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1
Søiland, Anne Karin. "Silicon for Solar Cells". Doctoral thesis, Norwegian University of Science and Technology, Department of Materials Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-565.
Testo completoAbstract (sommario):
This thesis work consists of two parts, each with a different motivation. Part II is the main part and was partly conducted in industry, at ScanWafer ASA’s plant no.2 in Glomfjord.
The large growth in the Photo Voltaic industry necessitates a dedicated feedstock for this industry, a socalled Solar Grade (SoG) feedstock, since the currently used feedstock rejects from the electronic industry can not cover the demand. Part I of this work was motivated by this urge for a SoG- feedstock. It was a cooperation with the Sintef Materials and Chemistry group, where the aim was to study the kinetics of the removal reactions for dissolved carbon and boron in a silicon melt by oxidative gas treatment. The main focus was on carbon, since boron may be removed by other means. A plasma arc was employed in combination with inductive heating. The project was, however, closed after only two experiments. The main observations from these two experiments were a significant boron removal, and the formation of a silica layer on the melt surface when the oxygen content in the gas was increased from 2 to 4 vol%. This silica layer inhibited further reactions.
Multi-crystalline (mc) silicon produced by directional solidification constitutes a large part of the solar cell market today. Other techniques are emerging/developing and to keep its position in the market it is important to stay competitive. Therefore increasing the knowledge on the material produced is necessary. Gaining knowledge also on phenomenas occurring during the crystallisation process can give a better process control.
Part II of this work was motivated by the industry reporting high inclusion contents in certain areas of the material. The aim of the work was to increase the knowledge of inclusion formation in this system. The experimental work was divided into three different parts;
1) Inclusion study
2) Extraction of melt samples during crystallisation, these were to be analysed for carbon- and nitrogen. Giving thus information of the contents in the liquid phase during soldification.
3) Fourier Transform Infrared Spectroscopy (FTIR)-measurements of the substitutional carbon contents in wafers taken from similar height positions as the melt samples. Giving thus information of the dissolved carbon content in the solid phase.
The inclusion study showed that the large inclusions found in this material are β-SiC and β-Si3N4. They appear in particularly high quantities in the top-cuts. The nitrides grow into larger networks, while the carbide particles tend to grow on the nitrides. The latter seem to act as nucleating centers for carbide precipitation. The main part of inclusions in the topcuts lie in the size range from 100- 1000 µm in diameter when measured by the Coulter laser diffraction method.
A method for sampling of the melt during crystallisation under reduced pressure was developed, giving thus the possibility of indicating the bulk concentration in the melt of carbon and nitrogen. The initial carbon concentration was measured to ~30 and 40 ppm mass when recycled material was employed in the charge and ~ 20 ppm mass when no recycled material was added. Since the melt temperature at this initial stage is ~1500 °C these carbon levels are below the solubility limit. The carbon profiles increase with increasing fraction solidified. For two profiles there is a tendency of decreasing contents at high fraction solidified.
For nitrogen the initial contents were 10, 12 and 44 ppm mass. The nitrogen contents tend to decrease with increasing fraction solidified. The surface temperature also decreases with increasing fraction solidified. Indicating that the melt is saturated with nitrogen already at the initial stage. The proposed mechanism of formation is by dissolution of coating particles, giving a saturated melt, where β-Si3N4 precipitates when cooling. Supporting this mechanism are the findings of smaller nitride particles at low fraction solidified, that the precipitated phase are β-particles, and the decreasing nitrogen contents with increasing fraction solidified.
The carbon profile for the solid phase goes through a maximum value appearing at a fraction solidified from 0.4 to 0.7. The profiles flatten out after the peak and attains a value of ~ 8 ppma. This drop in carbon content is associated with a precipitation of silicon carbide. It is suggested that the precipitation of silicon carbide occurs after a build-up of carbon in the solute boundary layer.
FTIR-measurements for substitutional carbon and interstitial oxygen were initiated at the institute as a part of the work. A round robin test was conducted, with the Energy Research Centre of the Netherlands (ECN) and the University of Milano-Bicocci (UniMiB) as the participants. The measurements were controlled against Secondary Ion Mass Spectrometer analyses. For oxygen the results showed a good correspondence between the FTIR-measurements and the SIMS. For carbon the SIMS-measurements were significantly lower than the FTIR-measurements. This is probably due to the low resistivity of the samples (~1 Ω cm), giving free carrier absorption and an overestimation of the carbon content.
2
Li, Dai-Yin. "Texturization of multicrystalline silicon solar cells". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/64615.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-111).
A significant efficiency gain for crystalline silicon solar cells can be achieved by surface texturization. This research was directed at developing a low-cost, high-throughput and reliable texturing method that can create a honeycomb texture. Two distinct approaches for surface texturization were studied. The first approach was photo-defined etching. For this approach, the research focus was to take advantage of Vall6ra's technique published in 1999, which demonstrated a high-contrast surface texture on p-type silicon created by photo-suppressed etching. Further theoretical consideration, however, led to a conclusion that diffusion of bromine in the electrolyte impacts the resolution achievable with Vallera's technique. Also, diffusion of photocarriers may impose an additional limitation on the resolution. The second approach studied was based on soft lithography. For this approach, a texturization process sequence that created a honeycomb texture with 20 ptm spacing on polished wafers at low cost and high throughput was developed. Novel techniques were incorporated in the process sequence, including surface wettability patterning by microfluidic lithography and selective condensation based on Raoult's law. Microfluidic lithography was used to create a wettability pattern from a 100A oxide layer, and selective condensation based on Raoult's law was used to reliably increase the thickness of the glycerol/water liquid film entrained on hydrophilic oxide islands approximately from 0.2 pm to 2.5 pm . However, there remain several areas that require further development to make the process sequence truly successful, especially when applied to multicrystalline wafers.
by Dai-Yin Li.
Ph.D.
3
Echeverria, Molina Maria Ines. "Crack Analysis in Silicon Solar Cells". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4311.
Testo completoAbstract (sommario):
Solar cell business has been very critical and challenging since more efficient and low costs materials are required to decrease the costs and to increase the production yield for the amount of electrical energy converted from the Sun's energy. The silicon-based solar cell has proven to be the most efficient and cost-effective photovoltaic industrial device. However, the production cost of the solar cell increases due to the presence of cracks (internal as well as external) in the silicon wafer. The cracks of the wafer are monitored while fabricating the solar cell but the present monitoring techniques are not sufficient when trying to improve the manufacturing process of the solar cells. Attempts are made to understand the location of the cracks in single crystal and polycrystalline silicon solar cells, and analyze the impact of such cracks in the performance of the cell through Scanning Acoustic Microscopy (SAM) and Photoluminescence (PL) based techniques.
The features of the solar cell based on single crystal and polycrystalline silicon through PL and SAM were investigated with focused ion beam (FIB) cross section and scanning electron microscopy (SEM). The results revealed that SAM could be a reliable method for visualization and understanding of cracks in the solar cells.
The efficiency of a solar cell was calculated using the current (I) - voltage (V) characteristics before and after cracking of the cell. The efficiency reduction ranging from 3.69% to 14.73% for single crystal, and polycrystalline samples highlighted the importance of the use of crack monitoring techniques as well as imaging techniques. The aims of the research are to improve the manufacturing process of solar cells by locating and understanding the crack in single crystal and polycrystalline silicon based devices.
4
Peters, Stefan. "Rapid thermal processing of crystalline silicon materials and solar cells /". Allensbach : UFO Atelier für Gestaltung und Verlag, 2004. http://www.loc.gov/catdir/toc/fy0805/2007493330.html.
Testo completo
5
Sheng, Xing Ph D. Massachusetts Institute of Technology. "Thin-film silicon solar cells : photonic design, process and fundamentals". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/105936.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 153-159).
The photovoltaic technology has been attracting widespread attention because of its effective energy harvest by directly converting solar energy into electricity. Thin-film silicon solar cells are believed to be a promising candidate for further scaled-up production and cost reduction while maintaining the advantages of bulk silicon. The efficiency of thin-film Si solar cells critically depends on optical absorption in the silicon layer since silicon has low absorption coefficient in the red and near-infrared (IR) wavelength ranges due to its indirect bandgap nature. This thesis aims at understanding, designing, and fabricating novel photonic structures for efficiency enhancement in thin-film Si solar cells. We have explored a previously reported a photonic crystal (PC) based structure to improve light absorption in thin-film Si solar cells. The PC structure combines a dielectric grating layer and a distributed Bragg reflector (DBR) for effcient light scattering and reflection, increasing light path length in the thin-film cell. We have understood the operation principles for this design by using photonic band theories and electromagnetic wave simulations. we discover that this DBR with gratings exhibit unusual light trapping in a way different from metal reflectors and photonic crystals. The light trapping effects for the DBR with and without reflector are numerically investigated. The self-assembled anodic aluminum oxide (AAO) technique is introduced to non- lithographically fabricate the grating structure. We adjust the AAO structural parameters by using different anodization voltages, times and electrolytes. Two-step anodization is employed to obtain nearly hexagonal AAO pattern. The interpore periods of the fabricated AAO are calculated by fast Fourier transform (FFT) analysis. We have also demonstrated the fabrication of ordered patterns made of other materials like amorphous Si (a-Si) and silver by using the AAO membrane as a deposition mask. Numerical simulations predict that the fabricated AAO pattern exhibits light trapping performance comparable to the perfectly periodic grating layer. We have implemented the light trapping concepts combining the self-assembled AAO layer and the DBR in the backside of crystalline Si wafers. Photoconductivity measurements suggest that the light absorption is improved in the near-IR spectral range near the band edge of Si. Furthermore, different types of thin-film Si solar cells, including a-Si, mi- crocrystalline Si ([mu]-Si) and micromorph Si solar cells, are investigated. For demonstration, the designed structure is integrated into a 1:5 [mu]m thick [mu]c-Si solar cell. We use numerical simulations to obtain the optimal structure parameters for the grating and the DBR, and then we fabricate the optimized structures using the AAO membrane as a template. The prototype devices integrating our proposed backside structure yield a 21% improvement in efficiency. This is further verified by quantum efficiency measurements, which clearly indicate stronger light absorption in the red and near-IR spectral ranges. Lastly, we have explored the fundamental light trapping limits for thin-film Si solar cells in the wave optics regime. We develop a deterministic method to optimize periodic textures for light trapping. Deep and high-index-contrast textures exhibit strong anisotropic scattering that is outside the regime of validity of the Lambertian models commonly used to describe texture-induced absorption enhancement for normal incidence. In the weak ab- sorption regime, our optimized surface texture in two dimensions (2D) enhances absorption by a factor of 2.7[pi]n, considerably larger than the classical [pi]n Lambertian result and exceeding by almost 50% a recent generalization of Lambertian model for periodic structures in finite spectral range. Since the [pi]n Lambertian limit still applies for isotropic incident light, our optimization methodology can be thought of optimizing the angle/enhancement tradeoff for periodic textures. Based on a modified Shockley-Queisser theory, we conclude that it is possible to achieve more than 20% efficiency in a 1:5 [mu]m thick crystalline Si cell if advanced light trapping schemes can be realized.
by Xing Sheng.
Ph. D.
6
Prönneke, Liv [Verfasser], e Jürgen [Akademischer Betreuer] Werner. "Fluorescent materials for silicon solar cells / Liv Prönneke. Betreuer: Jürgen Werner". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/102604359X/34.
Testo completo
7
Castellanos, Rodriguez Sergio. "Electrical impact assessment of dislocations in silicon materials for solar cells". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101529.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 117-133).
Cast multicrystalline silicon (mc-Si) makes up about 60% of the global photovoltaics market production, and is favored due to its lower areal and capex costs relative to monocrystalline silicon. This method, however, produces material with a higher density of defects (e.g., dislocations, grain boundaries, metal impurities) than more expensive single-crystalline growth methods. A higher density of defects, particularly dislocations, results in a greater density of charge-carrier recombination centers, which reduce a solar cell's efficiency. Interestingly, the recombination activity of individual dislocations and dislocation clusters can vary by orders of magnitude, even within the same device and a separation of only by millimeters of distance. In this thesis, I combine a surface-analysis approach with bulk characterization techniques to explore the underlying root cause of variations in recombination activity between different dislocation clusters. I propose and validate an optical inspection routine based on dislocations' surface characteristics to predict their recombination activity, and extend this methodology to novel growth processes. Lastly, I explore a spatial dispersion metric to assess its potential as a descriptor for the electrical recombination activity of clusters in silicon. This work provides tools to crystal growers and solar cell manufacturers that facilitate the evaluation of electrical performance at early stages of the cell processing, enabling them to reduce the time required for cycles of learning to improve crystal growth processes.
by Sergio Castellanos-Rodríguez.
Ph. D.
8
Chalfoun, Lynn Louise. "Process optimization of alloyed aluminum backside contacts for silicon solar cells". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10996.
Testo completo
9
Kang, Moon Hee. "Development of high-efficiency silicon solar cells and modeling the impact of system parameters on levelized cost of electricity". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47647.
Testo completoAbstract (sommario):
The objective of this thesis is to develop low-cost high-efficiency crystalline silicon solar cells which are at the right intersection of cost and performance to make photovoltaics (PV) affordable. The goal was addressed by improving the optical and electrical performance of silicon solar cells through process optimization, device modeling, clever cell design, fundamental understanding, and minimization of loss mechanisms. To define the right intersection of cost and performance, analytical models to assess the premium or value associated with efficiency, temperature coefficient, balance of system cost, and solar insolation were developed and detailed cost analysis was performed to quantify the impact of key system and financial parameters in the levelized cost of electricity from PV.
10
Kwapil, Wolfram [Verfasser]. "Alternative materials for crystalline silicon solar cells : risks and implications / Wolfram Kwapil". Konstanz : Bibliothek der Universität Konstanz, 2010. http://d-nb.info/1017235988/34.
Testo completo
11
Skarpeteig, Jon. "Cryogenic micro-photoluminescence of silicon solar cell materials". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11106.
Testo completoAbstract (sommario):
A literature review of relevant luminescence spectra for silicon solar cell materials has been performed. Three multi crystalline silicon samples in particular has been the focus of attention, one electronic grade sample R6, and two solar grade samples ES1, and MH2, where MH2 has added chromium. A list of relevant luminescence spectra has been compiled, and can be found in the appendix.The samples was measured using low temperature micro photoluminescence. They where cooled down by liquid helium in a cryostat, and excited using a laser. Photoluminescence was captured by a camera mounted on a spectrometer. Noise components was measured and removed, but are subject to changes in between measurements, causing some unwanted artifacts to appear in the end result.Luminescence due to P and B doping atoms are identified in ES1, and MH2 as expected, and a weak boron bound exciton line is also present in the clean sample R6. R6 also show signs of having a carbon-carbon complex impurity forming at grain boundaries. Lines attributed to chromium boron pairs where not observed in MH2, presumably due to the lack of such pairs. ES1 exhibits a luminescence attributed to a higher quality material, than both MH2, and R6. Expected behavior is for R6 to have such traits, but this is not the case. The reason for ES1 to show this enhanced luminescence is not known. Lines attributed to dislocations are observed in all the samples, but consist of less intense peaks than expected.Local heating is a severe problem using micro photoluminescence. Bound excitons, impurity lines, and dislocation related lines, all loose intensity at higher temperatures. The intrinsic TO line also have a substantial broadening with respect to energies, suggesting that local temperatures are as much as 70K higher than the sample holder temperature, when exciting with 128 mW using a 2 µm spot diameter.
12
Hudelson, George David Stephen III. "High temperature investigations of crystalline silicon solar cell materials". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50568.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 74-78).
Crystalline silicon solar cells are a promising candidate to provide a sustainable, clean energy source for the future. In order to bring about widespread adoption of solar cells, much work is needed to reduce their cost. Herein, I discuss the development of a new experimental technique to investigate solar cell materials under simulated processing conditions. I present the first applications and results using this technique, including observations of novel impurity interactions at elevated temperatures, and discuss their importance to the solar cell manufacturing process. One of the key drivers for reducing solar cell cost is developing a fundamental understanding of the behavior of defect and impurities in solar cell materials. Since solar cell processing occurs at high temperatures, experiments are needed that allow characterization of solar cell materials at high temperatures representative of manufacturing conditions, at the length-scales of the defects that are present. To achieve this, I have developed a novel in situ high temperature sample stage for measuring samples via synchrotron-based X-ray microprobe. This technique allows for mapping and chemical state determination of metal impurity clusters on the order of 100 nm to 100 [mu]m, over sample areas of several square millimeters, at temperatures in excess of 1200°C and under controlled ambient atmosphere. The application of this technique has yielded novel insights concerning the behavior of metal impurities at high temperature.
(cont.) For the first time, the phenomenon of retrograde melting (i.e. melting on cooling) has been observed in a semiconductor material. Internal gettering of dissolved metal to liquid metal-silicon droplets within the silicon matrix is observed. Understanding of this phenomenon provides the potential to improve solar cell devices by reducing the more-detrimental dissolved metal content within the material by concentrating it into precipitates. Finally, I provide results and a model that explains the formation and resulting morphology of mixed-metal silicide precipitates in multicrystalline silicon.
by George David Stephen Hudelson, III.
S.M.
13
Park, Jihong. "Electrical properties of polycrystalline solar cell silicon". Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1061389017.
Testo completo
14
Tahhan, Abdulla. "Energy performance enhancement of crystalline silicon solar cells". Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/14503.
Testo completoAbstract (sommario):
The work in this thesis examines the effects of the application of oxide coatings on the performance of the single crystalline silicon photovoltaic solar cells. A variety of potential oxide materials for solar cells performance enhancement are investigated. These films are silicon oxide, titanium oxide and rare earth ion-doped gadolinium oxysulfide phosphor. This study compares the electrical characteristics, optical properties and surface chemical composition of mono-crystalline silicon cells before and after coating. The first study investigates the potential for using single and double layers of silicon oxide films produced by low-temperature Plasma Enhanced Chemical Vapour Deposition (PECVD) using tetramethylsilane as a silicon precursor and potassium permanganate oxidising agent for efficiency enhancement of solar cells at low manufacturing cost. Deposition of the films contributes to the increase of the conversion energy of the solar cells on one hand while the variety of colours obtained in this study can be of great importance for building-integrated photovoltaic application on the other hand. The obtained results demonstrated a relative enhancement of 3% in the conversion efficiency of the crystalline silicon solar cell. In the second study, the effects of using a single layer of titanium oxide and a stack of silicon oxide and titanium oxide on the performance of solar cell are demonstrated. Moreover, this study shows the use of different sputtering configurations and oxidation methods. The experimental results showed a relative enhancement of 1.6% for solar cells coated with a stack of silicon oxide/titanium oxide. In the third study, silicon cells were coated with a luminescent layer consisting of down-converting phosphor, gadolinium oxysulfide doped with erbium and terbium, and a polymeric binder of EVA using doctor-blade screen printing technique. A relative enhancement of 4.45% in the energy conversion efficiency of PV solar cell was achieved. Also, the effects of combining silicon oxide layers together with the luminescent composite are also presented in this study.
15
Ekhagen, Sebastian. "Silicon solar cells: basics of simulation and modelling : Using the mathematical program Maple to simulate and model a silicon solar cell". Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62611.
Testo completoAbstract (sommario):
The main goal of this thesis was to simulate a solar cell with the symbolic manipulation tool Maple and discuss the strength and weaknesses of using Maple instead of the already known simulation program PC1D. This was done mainly by solving the three essential differential equations governing the current density and excess electron and hole densities in the solar cell. This could be done easily by using known simplifications especially the low injection assumption. However it was also a success without using this particular simplification but the solutions had to be achieved using a numerical method instead of direct methods. The results were confirmed by setting up the same solar cell with PC1D. The conclusion is that Maple gives the user increased freedom when setting up the solar cell, however PC1D is easier to use if this freedom is not needed. At the end of this thesis a brief introduction is also made on the possibility of using Maple with a tandem cell setup instead of single junction.
16
Zeng, Lirong Ph D. Massachusetts Institute of Technology. "High efficiency thin film silicon solar cells with novel light trapping : principle, design and processing". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44392.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references.
One major efficiency limiting factor in thin film solar cells is weak absorption of long wavelength photons due to the limited optical path length imposed by the thin film thickness. This is especially severe in Si because of its indirect bandgap. This thesis invents a novel light trapping scheme, the textured photonic crystal (TPC) backside reflector, which can enhance path length by at least several hundred times the film thickness for sufficient absorption. Physical principles and design optimization of TPC are discussed in detail. Thin film Si solar cells integrated with the new back reflector are successfully fabricated and significant efficiency enhancement is demonstrated.The new back reflector combines a one-dimensional photonic crystal as a distributed Bragg reflector (DBR) and reflection grating. The DBR achieves near unity reflectivity in a wide omnidirectional bandgap completely covering the wavelengths needing light trapping, and the grating can diffract light into large oblique angles and form total internal reflection against the front surface of the cell. The unique combination of DBR and grating tightly confines light inside the cell, effectively changing the path length from the thickness of the cell to its width.The back reflector parameters and the antireflection coating are systematically optimized for thin film Si solar cells through simulation and experiments. A 2 [mu]m thick cell can achieve 54% efficiency enhancement using the optimized design.For proof of concept, the TPC back reflector is integrated with thick crystalline Si solar cells (675 [mu]m thick), which demonstrate external quantum efficiency enhancement up to 135 times in the wavelength range of 1000-1200 nm.
(cont.) To prove the theory on the intended application, top-contacted thin film Si solar cells integrated with the TPC back reflector are successfully fabricated using Si-on-insulator material through an active layer transfer technique. All cells exhibit strong absorption enhancement, similar to that predicted by simulation. The 5 [mu]m thick cells gained 19% short circuit current density improvement, despite machine problems during fabrication. The textured photonic crystal back reflector design can be applied directly to single and poly-crystalline Si solar cells, and its principle is broadly applicable to other materials systems.
by Lirong Zeng.
Ph.D.
17
Fisher, Kate School of Photovoltaic & Renewable Energy Engineering UNSW. "The pitfalls of pit contacts: electroless metallization for c-Si solar cells". Awarded by:University of New South Wales. School of Photovoltaic and Renewable Energy Engineering, 2007. http://handle.unsw.edu.au/1959.4/29568.
Testo completoAbstract (sommario):
This thesis focuses on improving the adhesion of electroless metal layers plated to pit contacts in interdigitated, backside buried contact (IBBC) solar cells. In an electrolessly plated, pit contact IBBC cell, the contact grooves are replaced with lines of pits which are interconnected by the plated metal. It is shown, however, that electroless metal layers, plated by the standard IBBC plating sequence, are not adherent on pit contact IBBC solar cells. The cause of this adhesion problem is investigated by examining the adhesive properties of each of the metal layers in the electroless metallization sequence on planar test structures. This investigation reveals that Pd activation of heavily P diffused Si impedes Ni silicide growth and that, in the absence of a silicide at the Ni/Si interface, an electrolessly plated Cu layer will cause the underlying Ni layer to peel away from the substrate. It is also found that the Ni silicidation process itself intermittently causes the unreacted Ni to spontaneously peel away from the substrate. An electroless metallization sequence that results in thick, adhesive Cu deposits on planar < 100> surfaces is developed in this thesis. It is shown that this process leads to the formation of a Ni silicide on both n- and p- type, heavily diffused surfaces. Fully plated, pit contact IBBC solar cells were not able to be fabricated during the course of this work but it is reasonable to expect that the modified plating sequence developed in this work will result in the metal layers being adhesive on these cells.
18
Helland, Susanne. "Electrical Characterization of Amorphous Silicon Nitride Passivation Layers for Crystalline Silicon Solar Cells". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16310.
Testo completoAbstract (sommario):
High quality surface passivation is important for the reduction of recombination losses in solar cells. In this work, the passivation properties of amorphous hydrogenated silicon nitride for crystalline silicon solar cells were investigated, using electrical characterization, lifetime measurements and spectroscopic ellipsometry. Thin films of varying composition were deposited on p-type monocrystalline silicon wafers by plasma enhanced chemical vapor deposition (PECVD). Highest quality surface passivation was obtained for silicon-rich thin films, where a surface recombination velocity of 30 cm/s was obtained after a heat treatment corresponding to the industrial contact firing process. Electrical characterization of the interface between silicon nitride and silicon was performed by capacitance and conductance measurements. Several challenging aspects related to the interpretation of these measurements were investigated in detail, including charging and discharging, leakage currents, and frequency dependent capacitance.
19
Salomon, Ashley. "Oxygen precipitate studies in silicon for gettering in solar cell applications". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/114090.
Testo completoAbstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001.Cataloged from PDF version of thesis.
Includes bibliographical references (page 31).
Oxygen precipitates in silicon can be used (in a process called internal gettering) as sites of heterogeneous nucleation of precipitates of iron and other transition metal that are harmful to solar cell device operation. Oxygen precipitate densities in p- (10¹⁴ boron atoms/cm³) wafers were quantified using chemical etch techniques. The precipitate densities were then used to estimate times to getter iron based on a diffusion limited precipitation model. Oxygen precipitate densities in p++ (10¹⁹ boron atoms/cm³) wafers were quantified using chemical etch techniques. High levels of boron in p++ wafers make quantifying precipitate densities particularly difficult, via etching, or other methods because precipitate densities in highly doped wafers are very high and the size of precipitates small.
by Ashley Salomon.
S.B.
20
Murphy, Robert Clayton. "Effects of material inhomogeneity on the terminal characteristics of polycrystalline silicon solar cells /". Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Testo completo
21
Sauaia, Rodrigo Lopes. "Development and analysis of silicon solar cells with laser-fired contacts and silicon nitride laser ablation". Pontifícia Universidade Católica do Rio Grande do Sul, 2013. http://hdl.handle.net/10923/5499.
Testo completoAbstract (sommario):
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Previous issue date: 2013The goal of this thesis was the development and analysis of crystalline silicon solar cells processed by laser radiation. Solar cells with n+pp+ structure on p-type, CZ-Si solar grade substrate were developed, analysed, and evaluated, based on two laser processing techniques: laser-fired rear contacts (LFC) and laser ablation of the front surface silicon nitride by means of laser chemical processing (LPC) or using a mirror galvanometer laser system (SCA). The LFC method was employed to form the rear contacts of crystalline silicon solar cells after the deposition of an aluminium layer. The LCP and SOA methods were used to develop a silicon nitride ablation process. The laser ablation process was employed to open regions of the devices antireflection coating, followed by selective chemical deposition of Ni/Ag to form the front metal grid. The best laser processing parameters found for LFC solar cells were: 33. 0 A pumping lamp current, 20. 0 kHz q-switch frequency, and 0. 50 mm contact distance. LFC solar cells with screen printed front metallization and Si02 rear passivation layer achieved an average efficiency of 14. 4 % and best value of 15. 3 %, after an annealing step at 400 00 with a belt speed of 50 cm/min. lncreasing the rear aluminium layer thickness from 2 um to 4 um did not improve the performance of the devices significantly. The best laser processing parameters found for the silicon nitride laser ablation process based on the LCP technique were: 15. 3 uJ laser pulse energy, 16. 0 kHz q-switch frequency, and 100 mm/s processing speed. The best laser processing parameters found for the silicon nitride laser ablation process based on the SOA technique were: 5. 0 uJ laser pulse energy, 130. 0 kHz q-switch frequency, and 813 mm/s processing speed. Solar cells with silicon nitride laser ablation, front side metallization by Ni/Ag selective electrochemical deposition, and screen-printed rear side metallization achieved an average efficiency of 16. 1 % and best value of 16. 8 % for the LCP technique and an average efficiency of 16. 3 % and best value of 16. 6% for the SOA technique.
O objetivo desta tese foi o desenvolvimento e análise de células solares em substrato de silício cristalino com processamento por radiação laser. Células solares com estrutura n+pp+ em substrato de CZ-Si tipo p foram fabricadas, analisadas e comparadas, com base em duas técnicas de processamento laser: contatos posteriores formados por laser (CFL) e ablação do filme antirreflexo frontal de nitreto de silício por processamento químico com laser (PQL) ou por processamento com laser guiado por galvanômetro de espelhos (SCA). O método CFL foi utilizado na formação dos contatos posteriores de células solares, após a deposição de uma camada de alumínio. Os métodos PQL e SCA foram usados no desenvolvimento de um processo de ablação a laser do filme frontal de nitreto de silício. Trilhas foram abertas no filme antirreflexo e posteriormente metalizadas seletivamente por deposição química de níquel e prata, para formar a malha de metalização frontal. Os melhores parâmetros de processamento laser encontrados para células solares CFL foram: corrente da lâmpada de bombeamento óptico de 33,0 A, freqüência q-swttch de 20,0 kHz e distância entre contatos posteriores de 0,50 mm. Células solares CEL com metalização frontal por serigrafia e passivação posterior com SiO2 alcançaram uma eficiência média de 14,4 % e melhor valor de 15,3 %, após tratamento térmico a 400 °C com velocidade de esteira de 50 cm/min.O aumento da espessura da camada de alumínio posterior de 2 um para 4 um não resultou em melhora significativa da performance das células solares. Os melhores parâmetros de processamento encontrados para o processo de ablação a laser de nitreto de silício pela técnica PQL foram: energia do pulso laser de 15,3 uJ, frequência q-switch de 16,0 kHz e velocidade de processamento de 100 mm/s. Os melhores parâmetros de processamento encontrados para o processo de ablação a laser de nitreto de silicio pela técnica SCA foram: energia do pulso laser de 5,0 uJ, freqüência q-switch de 130,0 kHz e velocidade de processamento de 813 mm/s. Células solares com ablação a laser de nitreto de silicio, metalização frontal seletiva por deposição química de níquel e prata e metalização posterior por serigrafia atingiram a eficiência média de 16,1 % e o melhor valor de 16,8 % com a técnica PQL e a eficiência média de 16,3 % e melhor valor de 16,6 % com a técnica SCA.
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Coronel, Naomi (Naomi Cristina). "Investigation of porous alumina as a self-assembled diffractive element to facilitate light trapping in thin film silicon solar cells". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58066.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 33).
Thin film solar cells are currently being investigated as an affordable alternative energy source because of the reduced material cost. However, these devices suffer from low efficiencies, compared to silicon wafer solar cells, due to the poor absorption of longer wavelengths of light in the very thin active layer. One method of improving the efficiency of thin film solar cells is to use light trapping to increase the path length of long wavelength light to increase the probability of absorption. Previous work has yielded a new light trapping design, the textured photonic crystal, which incorporates a backside distributed Bragg reflector with a diffraction grating for large-angle diffraction. This study develops a simple and cost-effective fabrication method of using porous alumina as a self-assembled textured photonic crystal. Porous alumina is an attractive material because under certain anodization conditions, the pores form an ordered array. The ordered pore structure on the surface can serve as a diffraction grating, while alternating the pore size could vary the refractive index and form a distributed Bragg reflector. In this thesis, the arrangement of pores on the alumina surfaces is determined using a Fourier transform analysis. Results show that the average interpore distance of the samples depends linearly on the anodization voltage during pore initiation. These results will help to understand the pore initiation process and control that process to minimize fabrication steps.
by Naomi Coronel.
S.B.
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Gerrish, Nicole D. (Nicole Danielle) 1976. "A miniaturized single crystal silicon solar cell array for a MEMS power source". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85371.
Testo completo
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Michaud, Amadeo. "III-V / Silicon tandem solar cell grown with molecular beam epitaxy". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS247.
Testo completoAbstract (sommario):
Le photovoltaïque terrestre est actuellement largement dominé par des dispositifs à base de Silicium. La limite théorique d’efficacité de photoconversion pour les cellules solaires en silicium est de l’ordre de 29%. Avec des modules photovoltaïques ayant une efficacité de 26.3% sur le marché, la filière Si est à un niveau de maturité avancée et exploite déjà la quasi-totalité du potentiel de ce genre de cellule solaires. Le travail exposé ici traite d’une autre voie d’amélioration de l’efficacité de conversion des dispositifs photovoltaïques. En effet, les cellules solaires tandem, assemblées en empilant plusieurs cellules permettent de dépasser les limites associées aux cellules Si. La complémentarité importante des cellules solaire III-V avec les cellules Si permettrai en théorie d’atteindre plus de 40% d’efficacité. Cette thèse vise à l’élaboration de cellule III-V performante et compatible avec un usage en tandem. Dans un premier temps, l’épitaxie d’alliages phosphures a été étudiée et en particulier l’influence des conditions de croissance sur le GaInP. Une réduction de la pression en phosphore durant la croissance provoque des modulations de composition au sein de l’alliage. La température a un impact significatif sur la valeur de bande interdite qui diminue en augmentant la température. Des caractérisations de photoluminescence ont permis de définir les conditions optimales de croissance en maximisant le signal de luminescence de l’alliage. L’étude a notamment révélé que cru dans les conditions choisies, le GaInP présente moins de défaut et d’états profonds qu’à plus faibles températures de croissance. Enfin la capacité à atteindre des niveaux de dopages élevés dans l’alliage AlGaInP et l’impact de sa composition sur le dopage ont étés étudié. Dans un second temps, la structure des cellules solaires simple jonction GaInP a été optimisée. Nous illustrons l’impact de la passivation de la surface des cellules par AlInP et AlGaInP, ainsi que l’amélioration du photo-courant par l’amincissement de l’émetteur dopé n. L’introduction de couche non-dopée dans la structure ne permit pas de remédier au problème de collection des porteurs constaté dans les cellules. La couche limitant l’efficacité des cellules est composée de p-GaInP. Des caractérisations par Cathodoluminescence et Fluorescence résolue en temps d’échantillons identiques à cette couche ont été menées. Elles ont mis en avant une faible longueur de diffusion des porteurs générés dans le matériau. La comparaison de ces propriétés avec la littérature et celle mesurées pour GaInP épitaxié par MOCVD, indique que l’amélioration de l’efficacité des cellules passe par une augmentation de la mobilité des porteurs au sein du GaInP. Une solution pratique, combinant GaInP et AlGaAs dans une cellule à hétérojonction a été mise en œuvre. Ce type de structure est une autre perspective intéressante à l’avenir puisque des efficacités à l’état de l’art ont été mesurées. Enfin nous avons développé un procédé permettant d’adapter les cellules pour un usage tandem. Les structures sont crues en inversé puis transférées sur verre ou wafer de silicium sans endommager leur performance. Toutefois, des améliorations sont toujours nécessaires pour permettre l’assemblage d’une cellule tandem fonctionnelle. En effet, la non-planéité introduite par les contacts arrières de la cellule III-V cause actuellement des problèmes de collageTerrestrial photovoltaic is dominated by Silicon based devices. For this type of solar cells, the theory predicts an efficiency limit of 29%. With photovoltaic modules showing 26.6% efficiency already, Silicon-based modules is a mature technology and harvest almost their full potential. In this work, we intend to explore another path toward the enhancement of photovoltaic conversion efficiency. Tandem solar cells that consist in stacking sub-cells, allow to overcome the Si efficiency limit. Since solar cells made of III-V semiconductors are complementary to Silicon solar cells, theory predicts that efficiency above 40% is attainable when combining those types of cells. Here we focus on the elaboration of a performant III-V solar cell, compatible for a tandem use. The first stage of the PhD was to build know-how on phosphide alloys epitaxy with MBE. The influence of the growth conditions on GaInP properties was studied. We noted that composition modulations appear in the alloy when grown with low phosphorus pressure. The growth temperature also impacts the material bandgap, which reduces while increasing the temperature. Photoluminescence characterization served to select the best growth conditions by maximizing the photoluminescence efficiency. We could also highlight that in the conditions chosen, the GaInP exhibits less defect states. AlGaInP alloys are used for passivation purposes in the cells, the influence of the composition of the alloy on the Beryllium doping efficiency was studied. Then GaInP single junction solar cells were fabricated. The different layers composing the cells were optimized. The impact of the front surface passivation with AlGaInP and AlInP was emphasized; improvement of the cell photocurrent by the thinning of the n-doped GaInP layer was also demonstrated. The introduction of a non-intentionally-doped layer in the structure was tested in order to remedy the limits encountered with photocurrent collection. The p-GaInP composing the cells was eventually identified as the limiting factor. In depth characterization of samples mimicking the limiting layer was performed with cathodoluminescence and time-resolved fluorescence. A small diffusion length of the generated carriers was evidenced. Comparison with MOVPE and with literature values suggests that improving the carrier mobility in this layer is the main route to follow for improving of the GaInP cell efficiency. A practical solution was proposed and implemented: we designed a cell combining GaInP and AlGaAs in a heterojunction cell. This structure proves to be very relevant for the project since state of the art photoconversion efficiency of 18.7% was obtained. Finally a process was developed to adapt the III-V solar cells to the tandem configuration. Inverted PV cells structures were grown and transferred on glass or Silicon hosts without degradation of their efficiency. Further improvement of the process is needed to build a full tandem device, in particular the back metallization of the III-V cells must be compatible with the bonding of the cells on the host substrate
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Kirner, Simon [Verfasser], Bernd [Akademischer Betreuer] Rech, Bernd [Akademischer Betreuer] Stannowski e Miro [Akademischer Betreuer] Zeman. "Development of wide band gap materials for thin film silicon solar cells / Simon Kirner. Gutachter: Bernd Rech ; Miro Zeman. Betreuer: Bernd Rech ; Bernd Stannowski". Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1065665717/34.
Testo completo
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Charpentier, Coralie. "Investigation of deposition conditions and annealing treatments on sputtered ZnO:Al thin films : Material properties and application to microcristalline silicon solar cells". Phd thesis, Ecole Polytechnique X, 2012. http://tel.archives-ouvertes.fr/tel-00796955.
Testo completoAbstract (sommario):
La couche mince d'Oxyde Transparent Conducteur (OTC) utilisée en tant qu'électrode avant pour les cellules photovoltaïques silicium microcristallin est un matériau déterminant pour l'amélioration de leur rendement. Un OTC prometteur est l'oxyde de zinc dopé aluminium ZnO:Al déposé par pulvérisation cathodique magnétron RF. Une première partie du travail de thèse est dédiée à l'étude de l'influence des conditions de dépôt sur la microstructure, les mécanismes de croissance et les propriétés optoélectroniques du ZnO:Al. Nous avons ainsi obtenu un optimum en termes de transparence maximale dans le domaine visible et de résistivité minimale pour un dépôt réalisé à une pression de 0.12 Pa pour une température de 325 °C. Une seconde partie du travail de thèse porte sur l'effet de traitements après-dépôt, recuit thermique ou laser excimère, sur les propriétés du ZnO:Al déposé à température ambiante. L'influence de différentes atmosphères (sous-vide, N2/H2, et pur N2) et températures de recuit (de 400 à 500 °C) a été étudié. L'étape de recuit thermique a permis une amélioration notable des propriétés optoélectroniques de la couche ZnO:Al, jusqu'à une résistivité de 3.5×10-4 Ohm.cm pour une transmittance entre 400 et 1000 nm de 81.2%. L'étape de recuit laser, quant à elle, influe notamment les propriétés morphologiques du matériau. L'étape finale de ce travail de thèse est basée sur l'étude de la texturation chimique, étape ayant pour but la formation d'une morphologie de surface optimale, c'est-à-dire permettant le piégeage optique dans les couches actives silicium microcristallin et ce, sans altérer les qualités électriques de la couche. L'intégration de ces couches minces ZnO:Al en tant qu'électrode avant dans des cellules photovoltaïques PIN à base de silicium microcristallin à été et étudié en détail.
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Recht, Daniel. "Energetic Beam Processing of Silicon to Engineer Optoelectronically Active Defects". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10305.
Testo completoAbstract (sommario):
This thesis explores ways to use ion implantation and nanosecond pulsed laser melting, both energetic beam techniques, to engineer defects in silicon. These defects are chosen to facilitate the use of silicon in optoelectronic applications for which its indirect bandgap is not ideal. Chapter 2 develops a kinetic model for the use of point defects as luminescence centers for light-emitting diodes and demonstrates an experimental procedure capable of high-throughput screening of the electroluminescent properties of such defects. Chapter 3 discusses the dramatic change in optical absorption observed in silicon highly supersaturated (i.e., hyperdoped) with the chalcogens sulfur, selenium, and tellurium and reports the first measurements of the optical absorption of such materials for photon energies greater than the bandgap of silicon. Chapter 3 examines the use of silicon hyperdoped with chalcogens in light detectors and concludes that while these devices display strong internal gain that is coupled to a particular type of surface defect, hyperdoping with chalcogens does not lead directly to measurable sub-bandgap photoconductivity. Chapter 4 considers the potential for Silicon to serve as the active material in an intermediate-band solar cell and reports experimental progress on two proposed approaches for hyperdoping silicon for this application. The main results of this chapter are the use of native-oxide etching to control the surface evaporation rate of sulfur from silicon and the first synthesis of monocrystalline silicon hyperdoped with gold.Engineering and Applied Sciences
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Cruz, Bournazou Alexandros [Verfasser], Bernd [Akademischer Betreuer] Szyszka, Bernd [Akademischer Betreuer] Stannowski, Bernd [Gutachter] Szyszka, Bernd [Gutachter] Stannowski e Olindo [Gutachter] Isabella. "Transparent conductive oxides for silicon heterojunction solar cells: interaction between materials and device / Alexandros Cruz Bournazou ; Gutachter: Bernd Szyszka, Bernd Stannowski, Olindo Isabella ; Bernd Szyszka, Bernd Stannowski". Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1231908297/34.
Testo completo
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Togonal, Alienor. "Silicon Nanowires for Photovoltaics : from the Material to the Device". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX032/document.
Testo completoAbstract (sommario):
Les cellules solaires à base de nanofils de silicium offrent une alternative intéressante pour la réalisation de panneaux photovoltaïques à haut rendement et à faible coût. Elles bénéficient notamment des excellentes propriétés optiques des nanofils qui forment une surface à très faible réflectivité tout en piégeant efficacement la lumière. Dans cette thèse, nous utilisons et améliorons une méthode de gravure chimique peu coûteuse et industrialisable pour la fabrication de forêts de nanofils de silicium. En adaptant la mouillabilité du substrat et des nanofils, nous avons remédié au problème d'agglomération inhérent à cette méthode lorsqu’on veut obtenir des forêts denses et désordonnées de nanofils. En combinant cette méthode de gravure chimique à la lithographie assistée par nanosphères, nous avons pu fabriquer des réseaux ordonnés de nanofils avec un contrôle précis des propriétés géométriques (diametre des nanofils et distance entre eux). Les propriétés optiques de ces réseaux ont été étudiées théoriquement et expérimentalement afin d'identifier les configurations optimales. Nous avons ensuite fabriqué des cellules solaires à partir de ces différents types de nanofils et deux types de structures. Le premier type, des cellules solaires HIT (Hétérojonction avec couche mince Intrinsèque) à base de nanofils de silicium, a été fabriqué par RF-PECVD. L'optimisation des conditions de dépôt plasma nous a permis d'obtenir des cellules solaires hautement performantes: rendements de 12,9% et facteurs de forme au-delà de 80%. Le second type, des cellules solaires hybrides, est basé sur la combinaison d'une couche organique et des nanofils de silicium. La caractérisation des cellules fabriquées montre des rendements prometteurs. Enfin, nous présentons des résultats préliminaires pour transférer ces concepts à une technologie couches mincesSilicon Nanowire (SiNW) based solar cells offer an interesting choice towards low-cost and highly efficient solar cells. Indeed solar cells based on SiNWs benefit from their outstanding optical properties such as extreme light trapping and very low reflectance. In this research project, we have fabricated disordered SiNWs using a low-cost top-down approach named the Metal-Assisted-Chemical-Etching process (MACE). The MACE process was first optimized to reduce the strong agglomeration observed at the top-end of the SiNWs by tuning the wettability properties of both the initial substrate and the SiNWs surface. By combining the MACE process with the nanosphere lithography, we have also produced ordered SiNW arrays with an accurate control over the pitch, diameter and length. The optical properties of these SiNW arrays were then investigated both theoretically and experimentally in order to identify the geometrical configuration giving the best optical performance. Disordered and ordered SiNW arrays have been integrated into two types of solar cells: heterojunction with intrinsic thin layer (HIT) and hybrid devices. SiNW based HIT devices were fabricated by RF-PECVD and the optimization of the process conditions has allowed us to reach efficiency as high as 12.9% with excellent fill factor above 80%. Hybrid solar cells based on the combination of SiNWs with an organic layer have also been studied and characterized. The possible transfer of this concept to the thin film technology is finally explored
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Ek, Anton. "Silicon surface passivation via ultra-thin SiO2, TiO2, and Al2O3 layers". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75913.
Testo completoAbstract (sommario):
Energy traps at the silicon surface originating from discontinuities in the lattice is detrimental to the performance of solar cells. Acting as recombination centers, they offer a location where the charge carriers may easily return to their original energy band after excitation. Surface passivation is an effective method to combat this and can be done either by suppressing traps (lowering trap density) or by forming an electric field, preventing the carriers from reaching the defect states. Silicon oxide, SiO2, and aluminum oxide, Al2O3, are two materials which have previously been shown to provide good passivating qualities. In this thesis, SiO2 and Al2O3 have been used both as single layers and in a stack configuration to passivate the surface of crystalline silicon (c-Si). Using a response surface methodology approach, temperature optimization with respect to deposition and annealing temperature has been conducted for SiO2/Al2O3 stacks deposited with plasma-enhanced atomic layer deposition, PEALD. It was shown that the same deposition temperature (Tdeposition = 140 °C, Tanneal = 395 °C) could be used for both materials and provide good passivation with an effective surface recombination velocity, Seff, of 5.3 cm/s (1Ωcm n-type Si wafers). From FTIR measurements, an increase in hydroxyl groups was seen as the SiO2 deposition temperature increased while the opposite was observed for Al2O3 which also showed fewer carbon related impurities with increasing temperature. Increasing the SiO2 temperature strongly affected the fixed charge density, causing it to decrease and even switch polarity. The fixed charge density could also be controlled by varying the thickness of the intermediate SiO2 layer. At a thickness of 1-2 nm, a minimum in the effective lifetime was observed and was correlated to Si close to flat-band conditions. N-type wafers showed a larger negative fixed charge density than p-type wafers which results in stronger field-effect passivation. For phosphorous doped emitters (200 Ω/sq on 10 Ωcm p-type wafer), it was seen that SiO2/Al2O3 stacks with a SiNx anti-reflection coating performed better than SiO2 or Al2O3 single layers. By depositing SiO2 at 130 °C in SiO2/Al2O3 stacks and annealing at 450 °C, an implied open circuit voltage (iVoc) of 710 mV was measured (AM1.5G) together with an implied fill factor (iFF) of 84.1% and a recombination parameter (J0) of 19.2 fA/cm2. Al2O3 single layer showed an extremely low J0 of 10 fA/cm2 but suffered from a decreased iFF and strong injection dependent lifetimes which originates from an inversion layer. ALD ozone processes were successfully developed for SiO2 and Al2O3. The deposition rate per cycle for SiO2 was found to be only ~0.175 Ǻ/cycle (PEALD ~1.1 Ǻ/cycle), making it rather unpractical for use outside of research. Single layer SiO2 deposited with ozone showed, similarly to a plasma process, almost no surface passivation. Al2O3 however proved to be highly passivating on its own with a τeff = 3.8 ms, Seff = 1.2 cm/s (1 Ωcm n-type) after depositing at 250 °C. Studies on the effect of annealing showed that an annealing temperature of 450 °C is necessary to completely activate the passivation. The low Seff values were attributed to a very high negative fixed charge density ~1013 cm-2 together with strong chemical passivation.
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Kim, Ka-Hyun. "Hydrogenated polymorphous silicon : establishing the link between hydrogen microstructure and irreversible solar cell kinetics during light soaking". Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00747463.
Testo completoAbstract (sommario):
Cette thèse est consacrée au silicium polymorphe hydrogéné (pm-Si:H). Elle porte tout d'abord sur une étude du pm-Si :H puis sur une étude des cellules photovoltaïques fabriquées à partir de ce matériau. Le pm-Si:H est formé de couches minces nanostructurées et peut être déposé par PECVD conventionnelle. Les effets des différents paramètres de dépôt (mélanges gazeux, pression, puissance RF, température du substrat) sur les propriétés du matériau ont été étudiés pour optimiser sa qualité. La caractérisation des couches a été un enjeu primordial. Pour cela, nous avons choisi de combiner une palette très large de méthodes de caractérisation (ellipsomètrie spectroscopique, exodiffusion d'hydrogène, SIMS, FTIR, AFM, etc...). A cause de la contribution des nanoparticules de silicium dans le plasma, la nature du dépôt du pm-Si:H montre la différence contrairement au a-Si:H pour lequel le dépôt se fait par le biais de radicaux ionisés. L'étude des conditions du procédé nous a conduit à fabriquer des cellules solaires d'un rendement initial de 9.22 % avec un facteur de forme élevé (74.1), mais aussi de démontrer des effets de vieillissement inhabituels, tels que i) une dégradation initiale rapide, ii) une dégradation irréversible, et iii) de grands changements structuraux macroscopiques. Nous avons découvert que le principal problème se situe entre le substrat et la couche mince de silicium. L'hydrogène moléculaire diffuse et s'accumule à l'interface entre le substrat et la couche mince, ce qui introduit un délaminage local qui a pour conséquence une dégradation initiale rapide des performances des cellules. Nous avons trouvé que sous éclairement une structure PIN facilite l'accumulation d'hydrogène et le délaminage à l'interface entre le substrat et la couche dopée p. Cependant, l'utilisation d'une structure NIP empêche l'accumulation d'hydrogène et le délaminage. Cela nous a permis de fabriquer des cellules solaires pm-Si:H de structure NIP d'un rendement stable de 8.43 %, mais aussi de démontrer une degradation minimale (10 %) après un vieillissement de 500 heures.
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Kroely, Laurent. "Process and material challenges in the high rate deposition of microcrystalline silicon thin films and solar cells by Matrix Distributed Electron Cyclotron Resonance plasma". Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00550241.
Testo completoAbstract (sommario):
High deposition rates on large areas are industrial needs for mass production of microcrystalline silicon (μc-Si:H) solar cells. This doctoral work aims at exploring the usefulness of Matrix Distributed Electron Cyclotron Resonance (MDECR) plasmas to process the intrinsic layer of μc-Si:H p-i-n solar cells at high rates. With the high dissociation of silane achieved in MDECR plasmas, deposition rates as high as 6nm/s and 2.8nm/s have been demonstrated in our lab for amorphous and microcrystalline silicon respectively, without hydrogen dilution. This technique is also promising because it can be easily scaled up on large areas, just by extending the matrix of elementary microwave applicators. This subject was a unique opportunity to cover the whole chain of this field of research : A new MDECR reactor has been specially designed and assembled during this project. Its maintenance and its improvement have been important technical challenges : for example, the addition of a load-lock enabled us to lower the oxygen concentration in our films by a factor of 10. The impact of the deposition parameters (e.g. the ion energy, the substrate temperature, different gas mixtures, the microwave power) has been explored in extensive parametric studies in order to optimize the material quality. Great efforts have been invested in the characterization of the films. Our strategy has been to develop a wide range of diagnostics (ellipsometry, Raman spectroscopy, SIMS, FTIR, XRD, electrical characterizations etc.). Finally, p-i-n cells have been processed with the selected interesting materials. The successive successful improvements in the material quality (e.g. diffusion lengths of holes parallel to the substrate as high as 250 nm) did unfortunately not result in high efficiency solar cells. Their limited performance is in particular due to a very poor response in the red part of the spectrum resulting in low current densities. Consequently, the potential sources of limitation of the reactor, the material and the device have been studied : e.g. the presence of “cracks” prone to post-oxidation in the highly crystallized materials and the risk of deterioration of the ZnO substrate or of the p-doped layer by a too high process temperature or by hydrogen diffusing from the plasma.
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Ben, Dkhil Sadok. "Cellules solaires hybrides transparentes à base de nanofils de silicium et du poly(vinylcarbazole)". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10130.
Testo completoAbstract (sommario):
Le travail présenté dans ce mémoire porte sur la réalisation et l’étude des cellules solaires PV hybrides à réseaux interpénétrés utilisant les nanofils de silicium. Nos études ont porté essentiellement sur l’optimisation des structures hybrides à base de PVK ou de MEH-PPV mélangé dans leur volume avec une phase de nanofils de silicium, référant aux structures PVK/NFSi et MEH-PPV/NFSi respectivement. Cette étude a montré l’étroite interdépendance entre la morphologie des nanocomposites et les propriétés photovoltaïques des cellules réalisées. Nous avons étudiés l’influence de la concentration des nanofils de silicium sur le processus de dissociation des paires photo-générées. Nous avons également étudié l’effet des traitements thermiques et nous avons mis en évidence un meilleur transfert de charge dans le cas des structures PVK/NFSi. Nous avons aussi observé l’influence bénéfique de la désoxydation ainsi que le traitement de fonctionnalisation des nanofils sur l’amélioration du transfert de charge dans le cas des structures réalisées. En conclusion, nous avons montré que les cellules PV hybrides à réseaux interpénétrés utilisant les nanofils de silicium peuvent être optimisées grâce à la compréhension et au réglage fin du transfert de chargesThe work presented in this thesis focuses on the implementation and study of hybrid solar cells interpenetrating networks using silicon nanowires. Our studies have focused on the optimization of hybrid structures based PVK or MEH-PPV mixed in their volume with silicon nanowires phase, referring to structures PVK/NFSI and MEH-PPV/NFSI respectively. This study showed the close interdependence between morphology and properties of nanocomposites photovoltaic cells made. We studied the influence of the concentration of silicon nanowires on the dissociation process of photo-generated pairs. We also studied the effect of heat treatment and we have demonstrated a better load transfer in the case of structures PVK/NFSI. We also observed the beneficial effect of deoxidation treatment and functionalization of the nanowires on the improvement of charge transfer in the case of structures made. In conclusion, we have shown that the PV hybrid cell using silicon nanowires can be optimized through understanding and fine tuning of the charge transfer
34
Huang, Zhiquan. "Spectroscopic Ellipsometry Studies of Thin Film a-Si:H/nc-Si:H Micromorph Solar Cell Fabrication in the p-i-n Superstrate Configuration". University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1460919549.
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35
Kafka, Martin. "Fotoluminiscenční diagnostická metoda s transmisním osvětlením". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218153.
Testo completoAbstract (sommario):
The aim of this diploma thesis is an innovation of photoluminescence measure research workplace for measurement of cells structure defects by method of transmissive illumination while employing the current methods of measurement of defect in the solar cells structure. The first part deals with explanation of historical development of solar energy, of how we can reach production of electric power with contribution of solar radiation and defines usability of solar cells in practice. The thesis further analyses a practical application of measurement via laboratory diagnostic methods used by Department of Electrotechnology Brno University of Technology. The second part is focused on mechanical design of experimental photoluminescence measure workspace used for quick diagnostic defects employing the rear arousing source for detection of defects with assistance of transmissive system of illumination. Finally, with co-operation of SOLARTEC s.r.o. three types of solar cells are measured by this new method and compared with results of measurement via diagnostic methods of LBIV (Light Beam Induced Current), LBIC (Light Beam Induced Voltage), Electroluminescence, Photoluminescence, and detection defects by radiation of Microplasma.
36
Das, Saikat. "FUNDAMENTAL STUDIES OF SURFACTANT TEMPLATED METAL OXIDE MATERIALS SYNTHESIS AND TRANSFORMATION FOR ADSORPTION AND ENERGY APPLICATIONS". UKnowledge, 2015. http://uknowledge.uky.edu/cme_etds/48.
Testo completoAbstract (sommario):
This work addresses fundamental aspects of designing templates and curing conditions for the synthesis of mesoporous metal oxide thin films. The first section addresses selection of cationic-carbohydrate surfactant mixtures to synthesize templated silica thin films for selective adsorption of simple carbohydrates based on molecular imprinting. Nuclear magnetic resonance and fluorescence spectroscopy results suggest a novel structure for mixtures of alkyl glucopyranosides or xylopyranosides with cationic (trimethylammonium) surfactants. Despite thermodynamically favorable mixing, the carbohydrate headgroups in the mixed micelle adopt an inverted configuration with their headgroups in the micelle core, and therefore are inaccessible for molecular imprinting. This orientation occurs even when the alkyl tail length of the carbohydrate surfactant is greater than that of the cationic surfactant, but this limitation can be overcome by introducing a triazole linker to the carbohydrate surfactant. The next section addresses the effects of aging conditions on the structural and chemical evolution of surfactant templated silica thin films. The third section describes the synthesis of carbohydrate/cationic surfactant imprinted silica thin films with orthogonally oriented cylindrical pores by modifying the glass surface with a random copolymer. The last part of the dissertation addresses the effect of pore orientation on the transformation mechanism of block copolymer templated titania thin films during high temperature curing. Mesoporous titania thin films can be used for photochemical and solar cell applications, but doing so requires addressing the tradeoff between loss of mesostructural order and growth of crystallinity during thermal treatment. By using advanced x-ray scattering techniques it has been shown that the titania films with vertically oriented pores can better withstand the anisotropic stress that develops during thermal treatment compare to titania films with mixed pore orientation. For instance, films with parallel or mixed pores can only be heated at 400 °C for a brief time (~10 min) without loss of order, while orthogonally oriented films can be heated at 550 °C or greater for extended time periods (on the order of hours) without significant loss of long-range mesopore structure. Detailed kinetic modeling was applied to enable the comparison of activation energy for mesostructure loss in films as a function of pore orientation and thickness.
37
Landi, Giovanni [Verfasser]. "Organic semiconductor material and device characterization by low-frequency noise and admittance spectroscopy of polymer: fullerene solar cells and silicon/organic thin film heterodiodes / Giovanni Landi". Hagen : Fernuniversität Hagen, 2014. http://d-nb.info/1060847574/34.
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Nuys, Maurice René Verfasser], Uwe [Akademischer Betreuer] [Rau e Axel [Akademischer Betreuer] Lorke. "Characterization modification of copper and iron oxide nanoparticles for application as absorber material in silicon based thin film solar cells / Maurice René Nuys ; Uwe Rau, Axel Lorke". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1127143778/34.
Testo completo
39
Adhikari, Dipendra. "Optical and Microstructural Properties of Sputtered Thin Films for Photovoltaic Applications". University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1573118517150321.
Testo completo
40
Michard, Stephan Yann Verfasser], Uwe [Akademischer Betreuer] [Rau e Joachim [Akademischer Betreuer] Knoch. "Relation between growth rate, material quality, and device grade condition for intrinsic microcrystalline silicon : from layer investigation to the application to thin-film tandem solar cells / Stephan Yann Michard ; Uwe Rau, Joachim Knoch". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://d-nb.info/1127739654/34.
Testo completo
41
Michard, Stephan Yann [Verfasser], Uwe [Akademischer Betreuer] Rau e Joachim [Akademischer Betreuer] Knoch. "Relation between growth rate, material quality, and device grade condition for intrinsic microcrystalline silicon : from layer investigation to the application to thin-film tandem solar cells / Stephan Yann Michard ; Uwe Rau, Joachim Knoch". Aachen : Universitätsbibliothek der RWTH Aachen, 2015. http://nbn-resolving.de/urn:nbn:de:hbz:82-rwth-2015-012581.
Testo completo
42
Tarabsheh, Anas al. "Amorphous silicon based solar cells". kostenfrei, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29491.
Testo completo
43
Al, Tarabsheh Anas. "Amorphous silicon based solar cells". [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-29491.
Testo completo
44
Bett, Alexander Jürgen [Verfasser], e Stefan [Akademischer Betreuer] Glunz. "Perovskite silicon tandem solar cells : : two-terminal perovskite silicon tandem solar cells using optimized n-i-p perovskite solar cells". Freiburg : Universität, 2020. http://d-nb.info/1214179703/34.
Testo completo
45
Carton, Louise. "Mechanical properties of thin silicon wafers for photovoltaic applications : Influence of material quality and sawing process". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI107.
Testo completoAbstract (sommario):
Le wafer de silicium cristallin est le composant clé de la cellule solaire et représente une part significative du prix du module photovoltaïque. La réduction de l’épaisseur des wafers offre donc une voie privilégiée pour diminuer les coûts de production de l’énergie solaire. Le maintien de faibles taux de casse lors de la manipulation de ces fines plaquettes reste cependant un obstacle majeur. Dans ce contexte, il est primordial d’améliorer notre compréhension des mécanismes de fragilisation et de rupture des wafers. Ce travail étudie les propriétés mécaniques des wafers de silicium obtenus par découpe au fil diamanté. Nous avons développé une méthodologie de caractérisation mécanique adaptée à l’extrême fragilité de ces échantillons, en combinant des essais de rupture en flexion 4-lignes, biaxiale ainsi que des sollicitations dynamiques par chocs. En parallèle, des simulations par la méthode des éléments finis ont été implémentées afin de mieux comprendre les phénomènes en jeu. Des essais réalisés sur des échantillons bruts de découpe, attaqués chimiquement et recuits thermiquement ont révélé que l’endommagement le plus critique pour la défaillance mécanique se situe dans une couche de faible épaisseur inférieur à 3 µm) sous la surface, dont les propriétés sont contrôlées par l’étape de découpe. Au travers d’une vaste campagne de caractérisation sur des wafers de différentes épaisseurs (de 180 à 100 µm), nous avons montré que l’amincissement des plaquettes permet un gain de flexibilité sans diminution de la résistance mécanique intrinsèque, mais qui s’accompagne d’un risque plus élevé de rupture suite à un impact sur la tranche. Enfin, nous avons mis en évidence que les défauts structurels dans le silicium multicristallin et mono-like sont indirectement responsables de la diminution de la résistance à rupture des wafers : la difficulté accrue du fil à traverser ces défauts se traduit par des microfissures plus profondesThe crystalline silicon wafer is the key component of the solar cell and accounts for a significant portion of the total photovoltaic (PV) module cost. Reducing wafer thickness is therefore a privileged pathway to decrease solar energy production costs. Maintaining low breakage rates when processing such thin samples remains however challenging. In this context, it is essential to improve our understanding of the mechanisms responsible for wafer embrittlement and failure. This work investigates the mechanical properties of silicon wafers obtained using diamond wire sawing. We developed a mechanical characterization methodology suited for these thin, brittle samples, combining destructive tests with 4-line bending, biaxial bending and dynamic impacts. In parallel, finite element simulations were implemented to better understand the underlying phenomena. Tests performed on as-cut, chemically etched and annealed samples revealed that the most critical damage regarding mechanical failure is located within a thin subsurface layer (less than 3 µm), which properties are controlled by the sawing step. Through an extensive characterization campaign on wafers with different thicknesses (from 180 to 100 µm), we demonstrated that thinner samples exhibit an increased bending flexibility without alteration of their intrinsic mechanical strength, accompanied however by a higher risk of failure following an impact. Finally, we highlighted that the presence of structural defects in multicrystalline and mono-like silicon is indirectly responsible for the lower fracture strength of the wafers: the increased suffering of the diamond wire when cutting through these defects generates indeed deeper microcracks
46
Forster, Maxime. "Compensation engineering for silicon solar cells". Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00876318.
Testo completoAbstract (sommario):
This thesis focuses on the effects of dopant compensation on the electrical properties of crystalline silicon relevant to the operation of solar cells. We show that the control of the net dopant density, which is essential to the fabrication of high-efficiency solar cells, is very challenging in ingots crystallized with silicon feedstock containing both boron and phosphorus such as upgraded metallurgical-grade silicon. This is because of the strong segregation of phosphorus which induces large net dopant density variations along directionally solidified silicon crystals. To overcome this issue, we propose to use gallium co-doping during crystallization, and demonstrate its potential to control the net dopant density along p-type and n-type silicon ingots grown with silicon containing boron and phosphorus. The characteristics of the resulting highly-compensated material are identified to be: a strong impact of incomplete ionization of dopants on the majority carrier density, an important reduction of the mobility compared to theoretical models and a recombination lifetime which is determined by the net dopant density and dominated after long-term illumination by the boron-oxygen recombination centre. To allow accurate modelling of upgraded-metallurgical silicon solar cells, we propose a parameterization of these fundamental properties of compensated silicon. We study the light-induced lifetime degradation in p-type and n-type Si with a wide range of dopant concentrations and compensation levels and show that the boron-oxygen defect is a grown-in complex involving substitutional boron and is rendered electrically active upon injection of carriers through a charge-driven reconfiguration of the defect. Finally, we apply gallium co-doping to the crystallization of upgraded-metallurgical silicon and demonstrate that it allows to significantly increase the tolerance to phosphorus without compromising neither the ingot yield nor the solar cells performance before light-induced degradation.
47
Schultz, Oliver. "High-efficiency multicrystalline silicon solar cells". München Verl. Dr. Hut, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=977880567.
Testo completo
48
Osorio, Ruy Sebastian Bonilla. "Surface passivation for silicon solar cells". Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:46ebd390-8c47-4e4b-8c26-e843e8c12cc4.
Testo completoAbstract (sommario):
Passivation of silicon surfaces remains a critical factor in achieving high conversion efficiency in solar cells, particularly in future generations of rear contact cells -the best performing cell geometry to date. In this thesis, passivation is characterised as either intrinsic or extrinsic, depending on the origin of the chemical and field effect passivation components in dielectric layers. Extrinsic passivation, obtained after film deposition or growth, has been shown to improve significantly the passivation quality of dielectric films. Record passivation has been achieved leading to surface recombination velocities below 1.5 cm/s for 1 Ωcm n-type silicon covered with thermal oxide, and 0.15 cm/s in the same material covered with a thermal SiO2/PECVD SiNx double layer. Extrinsic field effect passivation, achieved by means of corona charge and/or ionic species, has been shown to decrease by 3 to 10 times the amount of carrier recombination at a silicon surface. A new parametrisation of interface charge, and electron and hole recombination velocities in a Shockley-Read-Hall extended formalism has been used to model accurately silicon surface recombination without the need to incorporate a term relating to space-charge or surface damage recombination. Such a term is unrealistic in the case of an oxide/silicon interface. A new method to produce extrinsic field effect passivation has been developed in which charge is introduced into dielectric films at high temperature and then permanently quenched in place by cooling to room temperature. This approach was investigated using charge due to one or more of the following species: ions produced by corona discharge, Na+, K+, Cs+, Mg2+ and Ca2+. It was implemented on both single SiO2 and double SiO2/SiNx dielectric layers which were then measured for periods of up to two years. The decay of the passivation was very slow and time constants of the order of 10,000 days were inferred for two systems: 1) corona-charge-embedded into oxide grown on textured FZ-Si, and 2) potassium ions driven into an oxide on planar FZ-Si. The extrinsic field effect passivation methods developed in this work allow more flexibility in the combined optimisation of the optical properties and the chemical passivation properties of dielectric films on semiconductors. Increases in cell Voc, Jsc and η parameters have been observed in simulations and obtained experimentally when extrinsic field effect passivation is applied to the front surface of silicon solar cells. The extrinsic passivation reported here thus represents a major advancement in controlled and stable passivation of silicon surfaces, and shows great potential as a scalable and cost effective passivation technology for solar cells.
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Zhu, Mingxuan. "Silicon nanowires for hybrid solar cells". Ecole centrale de Marseille, 2013. http://tel.archives-ouvertes.fr/docs/00/94/57/87/PDF/The_manuscript-4.pdf.
Testo completo
50
McCann, Michelle Jane, e michelle mccann@uni-konstanz de. "Aspects of Silicon Solar Cells: Thin-Film Cells and LPCVD Silicon Nitride". The Australian National University. Faculty of Engineering and Information Technology, 2002. http://thesis.anu.edu.au./public/adt-ANU20040903.100315.
Testo completoAbstract (sommario):
This thesis discusses the growth of thin-film silicon layers suitable for solar cells using
liquid phase epitaxy and the behaviour of oxide LPCVD silicon nitride stacks on silicon
in a high temperature ambient.¶
The work on thin film cells is focussed on the characteristics of layers grown using liquid
phase epitaxy. The morphology resulting from different seeding patterns, the transfer of
dislocations to the epitaxial layer and the lifetime of layers grown using oxide compared
with carbonised photoresist barrier layers are discussed. The second half of this work
discusses boron doping of epitaxial layers. Simultaneous layer growth and boron doping
is demonstrated, and shown to produce a 35um thick layer with a back surface field
approximately 3.5um thick.¶
If an oxide/nitride stack is formed in the early stages of cell processing, then characteristics of the nitride may enable increased processing flexibility and hence the realisation
of novel cell structures. An oxide/nitride stack on silicon also behaves as a good anti-
reflection coating. The effects of a nitride deposited using low pressure chemical vapour
deposition on the underlying wafer are discussed. With a thin oxide layer between the
silicon and the silicon nitride, deposition is shown not to significantly alter effective life-times.¶
Heating an oxide/nitride stack on silicon is shown to result in a large drop in effective
Lifetimes. As long as at least a thin oxide is present, it is shown that a high temperature
nitrogen anneal results in a reduction in surface passivation, but does not significantly
affect bulk lifetime. The reduction in surface passivation is shown to be due to a loss of
hydrogen from the silicon/silicon oxide interface and is characterised by an increase in
Joe. Higher temperatures, thinner oxides, thinner nitrides and longer anneal times are all
shown to result in high Joe values. A hydrogen loss model is introduced to explain the
observations.¶
Various methods of hydrogen re-introduction and hence Joe recovery are then discussed
with an emphasis on high temperature forming gas anneals. The time necessary
for successful Joe recovery is shown to be primarily dependent on the nitride thickness
and on the temperature of the nitrogen anneal. With a high temperature forming gas
anneal, Joe recovery after nitrogen anneals at both 900 and 1000oC and with an optimised
anti-reflection coating is demonstrated for chemically polished wafers.¶
Finally the effects of oxide/nitride stacks and high temperature anneals in both nitrogen
and forming gas are discussed for a variety of wafers. The optimal emitter sheet
resistance is shown to be independent of nitrogen anneal temperature. With textured
wafers, recovery of Joe values after a high temperature nitrogen anneal is demonstrated
for wafers with a thick oxide, but not for wafers with a thin oxide. This is shown to be
due to a lack of surface passivation at the silicon/oxide interface.