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1
Xu, Wenwei. "Carrier transport characterization and thin film transistor applications of amorphous organic electronic materials." HKBU Institutional Repository, 2013. http://repository.hkbu.edu.hk/etd_ra/1542.
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Alexiou, I. "Hole transport materials for organic thin films." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595437.
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The aim of this project is to prepare and characterise novel triarylamine-based hole transport materials for xerographic applications that exhibit favourable electrochemical properties and amorphous nature. As an introduction, the six steps of the xerographic process and the common classes of hole transporting materials are described. The basic theories that have been developed for charge transport are discussed and an overview of the palladium-mediated amination and Suzuki reactions is given. In the following chapters, the synthesis and characterisation of a number of hole transporting triarylamines is reported. A series of linear trimeric arylamines is synthesised using the palladium-catalysed Suzuki protocol and their properties were determined using cyclic voltammetry, thermal gravimetric analysis and differential scanning calorimetry. Similar characterisation is carried out for a number of relatively unsubstituted phenyl and thiophene-based triarylamines. The synthesis of a series of oligomeric materials based on MPPD (Bis-methoxyphenyl-diphenyl-biphenyl-diamine) is reported and their electrochemical and thermal properties are investigated. Thiophene and dioctyl-fluorene-substituted MPPD-derivatives are studied as hole transport materials. Star-shaped and dendritic triarylamines with biphenyl and bithiophene-core molecules are also prepared using palladium-mediated chemistry and characterised. Finally, the attempts to synthesise macrocyclic triarylamine hole transporting materials are described in detail. The charge carrier properties for some of the synthesised materials are measured using the time-of-flight technique of using field-effect-transistors. Each set-up is described in detail and the hole mobility of the materials is calculated. A correlation between structural characteristics and charge-transporting properties is attempted.
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Mohamed, Norani M. "Electrical and optical properties of organic materials." Thesis, University of Essex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333723.
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Chen, Danti. "Local electron transport of organic semiconducting monolayers /." Connect to online version, 2009. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2009/363.pdf.
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Dalkiranis, Pereira Gustavo Gonçalves. "Thermal transport and thermoelectricity in organic and inorganic thin films." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667873.
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Yang, Dengliang. "Charge transport and chemical sensing properties of organic thin-films." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3262181.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed July 10, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 104-113).
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Limketkai, Benjie 1982. "Charge-carrier transport in amorphous organic semiconductors." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43063.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 101-106).
Since the first reports of efficient luminescence and absorption in organic semiconductors, organic light-emitting devices (OLEDs) and photovoltaics (OPVs) have attracted increasing interest. Organic semiconductors have proven to be a promising material set for novel optical and/or electrical devices. Not only do they have the advantage of tunable properties using chemistry, but organic semiconductors hold the potential of being fabricated cheaply with low temperature deposition on flexible plastic substrates, ink jet printing, or roll-to-roll manufacturing. These fabrication techniques are possible because organic semiconductors are composed of molecules weakly held together by van der Waals forces rather than covalent bonds. Van der Waals bonding eliminates the danger of dangling bond traps in amorphous or polycrystalline inorganic films, but results in narrower electronic bandwidths. Combined with spatial and energetic disorder due to weak intermolecular interactions, the small bandwidth leads to localization of charge carriers and electron-hole pairs, called excitons. Thus, the charge-carrier mobility in organic semiconductors is generally much smaller than in their covalently-bonded, highly-ordered crystalline semiconductor counterparts. Indeed, one major barrier to the use of organic semiconductors is their poor charge transport characteristics. Yet this major component of the operation of disordered organic semiconductor devices remains incompletely understood. This thesis analyzes charge transport and injection in organic semiconductor materials. A first-principles analytic theory that explains the current-voltage characteristics and charge-carrier mobility for different metal contacts and organic semiconductor materials over a wide range of temperatures, carrier densities, and electric field strengths will be developed.
(cont) Most significantly, the theory will enable predictive models of organic semiconductor devices based on physical material parameters that may be determined by experimental measurements or quantum chemical simulations. Understanding charge transport and injection through these materials is crucial to enable the rational design for organic device applications, and also contributes to the general knowledge of the physics of materials characterized by charge localization and energetic disorder.
by Benjie N. Limketkai.
Ph.D.
8
Limketkai, Benjie 1982. "Charge carrier transport in amorphous organic semiconductors." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87446.
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Benedetto, Alessandro. "Grafting organic thin films for the lubrification of electrical contacts." Paris 11, 2008. http://www.theses.fr/2008PA112352.
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Au cours de cette thèse a été étudié le rôle de films minces organiques immobilisés comme lubrifiants pour les contacts électriques. Les films minces ont été électrogreffés sur or qui est un métal couramment utilisé comme revêtement métallique final de certains connecteurs électriques bas-niveau. Les films étudiés appartiennent à deux familles : les poly(methacrylate)s obtenus par électrogreffage cathodique et des films de type poly(phenylene) obtenus par la réduction électrochimique de sels de diazonium aromatiques. Des films composites de poly(methacrylate) électrogreffés avec des nanotubes de carbone ou des polymères conducteurs ont été aussi réalisés. D’abord le comportement électrochimique des molécules de départ puis le greffage électrochimique des films ainsi que leur propriétés physico-chimiques ont été étudiés. Ensuite des tests tribologiques et électriques ont été effectués sur les substrats fonctionnalisés pour étudier l’effet lubrifiant des films organiques et la résistance électrique du contact ainsi protégé. Les recherches effectuées au cours de cette thèse ont mené à l’identification des films minces électrogreffés qui réduisent efficacement le frottement et l’usure des substrats métalliques en préservant des résistances électriques de contact satisfaisantes du même ordre qu’un contact direct or/orIn this thesis thin organic grafted films have been studied as lubrifiant for electrical contacts. Thin film were electrografted on gold which is currently used for the final metallic layer of some common low-level electrical connectors. Two families have been studied : the cathodic electrografted poly(methacrylate)s and the poly(phenylene)-like films obtained by the reduction of aromatic diazonium salts. Composite films have also been fabricated between the electrografted poly(methacrylate) and carbon nanotubes or conducting polymers in order to ameliorate electrical conduction properties. First the physical chemistry properties of the film have been studied and in particular the electrochemical behaviour of the molecules used as building blocks, the electrochemical grafting of the molecules used as building blocks, the electrochemical grafting of the films and the film surface physical chemistry properties. Then tribological and electrical tests were effectuated to study the lubrication effect obtained upon substrate functionalization by the organic films and their effect on the contact electrical resistance. The researches effectuated during this thesis allowed for the identification of thin electrografted films capable of effective reduction of friction and wear of gold substrates preserving low electrical resistances
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Krause, Stefan. "Determination of the transport levels in thin films of organic semiconductors." Doctoral thesis, kostenfrei, 2009. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2009/4047/.
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Park, June Hyoung. "Charge transport in organic multi-layer devices under electric and optical fields." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1182273300.
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Madigan, Conor (Conor Francis) 1978. "Aspects of exciton behavior in amorphous organic thin films." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87250.
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Shamba, Precious. "MOCVD growth and electrical characterisation of InAs thin films." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/706.
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In this work, a systematic study relating the surface morphologies, electrical and structural properties of both doped and undoped InAs and InAsSb epitaxial films grown by metalorganic chemical vapour deposition (MOCVD) was undertaken. A comparative study using TBAs and AsH3 as the group V source in the growth of InAs revealed a considerable improvement, primarily in the electrical properties of InAs grown using TBAs with no significant difference in the surface morphology. InAs layers grown using TBAs, exhibited superior 77 K mobilities of up to 46 000 cm2/Vs, exceeding the best MOCVD data to date. The feasibility of tetraethyl tin (TESn) as an n-type dopant in InAs was to our knowledge investigated for the first time. The incorporation efficiency of this dopant was extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that the doping efficiency is temperature dependent and is not influenced by a variation of the V/III ratio or substrate orientation. Furthermore, Sn doping concentrations could be controlled over 2 orders of magnitude ranging between 2.7 x 1017 and 4.7 x 1019 cm-3 with 77 K mobilities ranging from 12 000 to 1300 cm2/Vs. The electrical properties of zinc doped InAs employing dimethyl zinc (DMZn) as the ptype dopant, were studied as a function of V/III ratio and substrate orientation. The effect of a variation of these parameters on the structural properties and surface morphology of InAs is also reported. The substrate orientation appears to have no influence on the Zn incorporation. An increase in Zn incorporation resulted in a deterioration of both the surface morphology and structural quality of the InAs layers. The incorporation efficiency of DMZn in InAsSb was studied as a function of growth temperature, V/III ratio and DMZn flow rate. A higher Zn incorporation was observed in InAsSb epitaxial layers grown at a lower temperature and V/III ratio as opposed to the layers grown at a higher temperature and V/III ratio. This study also revealed that the use of DMZn caused a dopant memory effect. A two-layer model proposed by Nedoluha and Koch (1952) was used to simulate the Hall measurements of Zn doped InAs and InAsSb in order to correct the shortcomings of conventional Hall measurements in determining the electrical properties exhibited by these materials.
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Pevzner, Boris. "Transport and dielectric properties of thin fullerene (C₆₀) films." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41403.
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Casalini, R. "Organic thin films : a comparison of their electrical and gas sensitivity." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4477/.
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This thesis presents a study of the electrical properties and gas sensitivity of thin films of four different organic materials. These are: (i) Langmuir-Blodgett (LB) films of tetrabutylammonium Ni(dmit)(_2) complex (Bu(_4)-Ni(dmit)(_2) complex) mixed with tricosanoic acid (TA); (ii) thin films of polypyrrole (PPy) mixed with palmitic acid (PA) obtained using the LB technique followed by two solid state reactions; (iii) cast films of polycyanopropylmethylsiloxane (PCMS); and (iv) LB films of a co-ordination polymer?5,5' methylenebis (N-hexadecylsalicydeneamine) (MBSH) (poly(CuMBSH)). LB films of (Bu(_4)-Ni(dmit)(_2) complex)/TA were characterised by electrical measurements?(AC in the frequency range 10(^2)-10(^6) Hz) at room temperature. For the other three types of films, characterisation of the structure and electrical behaviour (DC and AC in the frequency range 10(^2)-10(^6) Hz) on varying the temperature (in the range 90 - 298 K) and during the exposure to benzene, ethanol, acetonitrile and water (concentrations in the range 10(^2) -10(^5) ppm) was undertaken. During exposure to vapours, reversible changes in the electrical properties of the films were observed. The electrical behaviour and the changes during exposure to vapours were interpreted in terms of models in the literature, assuming a bulk dissolution of the vapours in the organic films. In all cases an 'anomalous' response to water was observed. For poly(CuMBSH), this effect was interpreted in terras of a Low Frequency Dispersion. The device characteristics for gas sensing applications are also discussed. Estimated minimum detectable concentrations were between 1-100 ppm for the three organic solvent vapours. Moreover, it is shown that the fi-equency behaviour for the admittance changes of the PCMS and poly(CuMBSH) devices could be exploited for the improvement of the sensitivity of a single device. The unique response of all the films to water vapour could be useful for its discrimination.
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Ramanan, Sulinya. "Elastomeric contact printing for sub-micron patterning of organic films." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77034.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 87-89).
In this thesis, a novel diffusion-based contact-printing technology is investigated, by which a wide variety of low molecular weight organic materials can be patterned without added temperature, pressure, or chemical processing, with just the use of relief-patterned polymeric (PDMS) stamps. It is determined that the diffusion of organic molecules into the polymer matrix is a solvent-assisted process in which mobile oligomers aid in the removal of organic material. It is further shown that using composite stamps, organic films can be patterned at a sub-100 nm length scale. Among other features, this patterning process has enabled patterning of Organic Light Emitting Diodes on a wavelength scale to reduce total internal reflection and thereby enhance the outcoupling of light from the device.
by Sulinya Ramanan.
M.Eng.
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Schweizer, Thomas Martin. "Electrical characterization and investigation of the piezoresistive effect of PEDOT:PSS thin films." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-04172005-231324/unrestricted/schweizer%5Fthomas%5Fm%5F200505%5Fmast.pdf.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2005.Kippelen, Bernard, Committee Member ; Brand, Oliver, Committee Chair ; Allen, Mark G., Committee Member. Includes bibliographical references.
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Niroui, Farnaz. "Electromechanical modulation of electrical conduction through organic thin films for switching applications." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84387.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-105).
Nanoelectromechanical (NEM) switches exhibit abrupt switching behavior and near-zero leakage current making them promising alternatives to conventional semiconductor switches. However, they require high actuation voltages and commonly suffer from permanent adhesion of device components leading to failure. This thesis proposes a novel NEM switch, or "squitch", that overcomes these challenges by electromechanical modulation of tunneling current through a nanometer-thick gap defined by an organic thin-film sandwiched between two electrodes. The switching is initiated by an applied voltage compressing the organic film to reduce the tunneling width leading to an exponential increase in the tunneling current. The deformed organic material prevents direct contact of the electrodes, while also providing the restoring force necessary to turn off the switch when the electrostatic force is removed, mitigating stiction-induced failure. In this thesis, the feasibility of the proposed switching mechanism is investigated through theoretical analysis of two- and three-terminal devices, demonstrating the possibility of energy efficient operation in the sub-1 V regime, with nanoseconds switching time and a large on-off current ratio of greater than 106. Based on the theoretical studies, design requirements are identified to guide the fabrication process of the proposed devices. Various methods of fabricating these devices have been developed, the details of which are outlined in this work.
by Farnaz Niroui.
S.M.
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Mohamad, Syed Abdul Malik Syed. "Electrical studies on hybrid MIS structures incorporating CdS nanoparticles in organic films." Thesis, Sheffield Hallam University, 2005. http://shura.shu.ac.uk/20004/.
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This project involves the investigation of a.c. and d.c. electrical characterisations and low-frequency noise properties of Langmuir-Blodgett (LB) films in metal-insulator-semiconductor (MIS) structure. Two types of insulating films based on hybrid organic-inorganic materials sandwiched between metal and semiconductor were fabricated. The original insulating films (untreated) were 40 layers Y-type LB films of Cd-salt stearic acid (CdSt[2]). The second type of insulating films were formed after the treatment of CdSt[2] films with H[2]S gas over a period of 12 hours at room temperature to grow CdS nanoparticles within the stearic acid matrix (treated). The capacitance-voltage (C-V) measurement of CdSt[2] LB films exhibit significant dependence on the measurement frequency in the accumulation region due to high d.c. leakage currents. By embedding CdS nanoparticles into the stearic acid matrix, less frequency dependent C-V curves were obtained. The problem in determining the true insulator capacitance due to frequency dispersion was overcome by using the Yang's model. The corresponding dielectric constant of LB films of CdSt[2] was found to be 2.3 and increased to 5.1 when embedded with CdS nanoparticles. The results from the dielectric loss measurement show that both devices agree well with Goswami and Goswami model. By incorporating CdS nanoparticles in the stearic acid matrix, the dielectric loss was found to increase which could be due to electrons being trapped by the CdS nanoparticles. A large current density was observed in the untreated devices at room temperature giving evidence of a leaky dielectric. The analysis of the temperature dependent I-V characteristics shown that current is independent of temperature, similar to the results published by several researchers which explained the current conduction mechanism in term of electron hopping and tunnelling through each bilayer of the LB films. In contrast, by embedding the CdS nanoparticles in the stearic acid matrix the currents have reduced by one-order of magnitude. The temperature dependence of the I-V characteristics showed the dependence of current on the device temperature at low electric field densities whilst less temperature dependence was observed at higher electric field density. Further investigation into the carrier transport mechanism, has found that the Poole-Frenkel effect was the dominant mechanism in the treated devices. A low frequency noise measurement setup has been designed and validated. The results of low-frequency noise measurement reported here are new. 1 / f noise was the only low-frequency noise observed in treated and untreated devices for frequencies up to 1kHz. The current noise spectral density S[I](f), was found to fit well with themodified Hooge's empirical model; [mathematical formula] where C, /, and f are noisemagnitude, current and frequency respectively. The exponential values of gamma and beta were found to lie within the acceptable ranges of 0.7 < gamma < 1.4 and 1 < beta < 3 respectively. The current noise power spectral density (PSD) at several fixed bias current was found to be dependent on the bias current with the PSDs for treated devices found to be approximately two-orders of magnitude higher. These results show that low-frequency noise measurement can be used to probe into the microstructure of the electron devices. It is believed that by embedding the CdS nanoparticles into the stearic acid matrix, electron trapping centres have been created which result in different current conduction behaviour from the untreated LB films of cadmium stearate.
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Ederth, Jesper. "Electrical Transport in Nanoparticle Thin Films of Gold and Indium Tin Oxide." Doctoral thesis, Uppsala University, Department of Materials Science, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3260.
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Electrical transport properties of nanoparticle gold films made by the gas evaporation method were analysed using resistivity measurements. Low temperature electrical transport measurements showed a cross-over from a temperature range dominated by inelastic scattering to a temperature range dominated by elastic scattering, presumably by grain boundaries. This cross-over shifted towards lower temperatures with increasing grain size.
High temperature in-situ electrical transport measurements were carried out in isothermal annealing experiments. Four types of samples, prepared at different deposition rates, were analysed. Samples prepared at low deposition rate displayed a higher thermal stability than samples prepared at high deposition rate. A relaxation model was fitted to the in-situ electrical transport data. The model included an activation energy, which was found to increase with increasing annealing temperature for all samples, thus pointing at the presence of pinning mechanisms in the samples.
Optical properties of nanoparticle gold films were investigated in the 0.3 < λ < 12.5 µm wavelength range. A model taking grain boundary scattering into account was successfully fitted to the experimental data and it was shown that the infrared reflectance decreased with decreasing grain size as a consequence of increased grain boundary scattering.
Nanoparticle tin-doped indium oxide films were made by spin-coating a dispersion containing the nanoparticles onto a substrate. The tin-doped indium oxide particles were prepared by a wet-chemical method. Optical properties were investigated in the 0.3 < λ < 30 µm wavelength range by reflectance and transmittance measurements. Effective medium theory was employed in the analyses of the optical data and information regarding film porosity and charge carrier concentration and mobility within the individual nanoparticles was obtained. It was found that ionized impurity scattering of the conduction electrons dominates within the particles. The temperature-dependent film resistivity was found to be governed by insulating barriers between clusters containing a large number of nanoparticles, thereby giving a negative temperature coefficient of resistivity.
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Hreha, Richard Douglas. "Studies on the synthesis and the transport properties of organic materials." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289977.
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A series of photo-crosslinkable arylamine-based hole-transport copolymers has been synthesized. The synthetic methodology employed allows for the redox potential of the polymer to be tuned by the incorporation of electron-donating or withdrawing moieties. Upon exposure to ultraviolet radiation, the copolymers become insoluble, as evidenced by ultraviolet-visible absorption spectroscopy. The ability to switch the solubility of the polymers enable one to photo-pattern the materials, a feature that is useful for the fabrication of multilayer organic light-emitting diodes (OLEDs) by solution processing techniques. OLEDs using the methacrylate based hole-transport polymers have been fabricated and the performance of the devices has been evaluated. 2,7-Bis(p-methoxyphenyl- m'-tolylamino)-9,9-dimethylfluorene, 2,7-bis(phenyl- m'-tolylamino)-9,9-dimethylfluorene, and 2,7-bis( p-fluorophenyl-m'-tolylamino)-9,9-dimethylfluorene have been synthesized using palladium-catalyzed reaction of the appropriate diarylamines with 2,7-dibromo-9,9-dimethylfluorene. These molecules have glass-transition temperatures 15-20°C higher than those for their biphenyl-bridged analogues, and are 0.11-0.14 V more easily oxidized. The hole mobilities of the three fluorene derivatives (blended with polystyrene) have been measured by the time-of-flight technique and are lower than the corresponding biphenyl-bridged analogues. Analysis of transport data according to the disorder formalism yields parameters similar to those for the biphenyl species, but with lower zero-field mobility values. Density functional theory based calculations suggest that the enforced planarization of the fluorene bridge leads to a larger reorganization energy, due to increased vibration contributions in the bridge for the neutral/cation electron-exchange reaction relative to the analogous biphenyl-bridged system. OLEDs have been fabricated using blends of the fluorene-bridged compounds with polystyrene as the hole-transport layer and Alq₃ as electron-transport layer and lumophore. Device performance shows a correlation with the ionization potential of the amine materials paralleling that seen in biphenyl-based systems. Monomers based on the fluorene bridged arylamine-based hole transport materials were also synthesized. Monomers having methacrylate, styrene, and norbornene moieties have been synthesized and their hole mobilities measured. Adding a methacrylate or norbornene moiety had no effect on the hole mobility. The mobility of the norbornene polymer was significantly higher than the methacrylate polymer.
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Pingel, Patrick. "Morphology, charge transport properties, and molecular doping of thiophene-based organic semiconducting thin films." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6980/.
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Organic semiconductors combine the benefits of organic materials, i.e., low-cost production, mechanical flexibility, lightweight, and robustness, with the fundamental semiconductor properties light absorption, emission, and electrical conductivity. This class of material has several advantages over conventional inorganic semiconductors that have led, for instance, to the commercialization of organic light-emitting diodes which can nowadays be found in the displays of TVs and smartphones. Moreover, organic semiconductors will possibly lead to new electronic applications which rely on the unique mechanical and electrical properties of these materials.
In order to push the development and the success of organic semiconductors forward, it is essential to understand the fundamental processes in these materials. This thesis concentrates on understanding how the charge transport in thiophene-based semiconductor layers depends on the layer morphology and how the charge transport properties can be intentionally modified by doping these layers with a strong electron acceptor.
By means of optical spectroscopy, the layer morphologies of poly(3-hexylthiophene), P3HT, P3HT-fullerene bulk heterojunction blends, and oligomeric polyquaterthiophene, oligo-PQT-12, are studied as a function of temperature, molecular weight, and processing conditions. The analyses rely on the decomposition of the absorption contributions from the ordered and the disordered parts of the layers. The ordered-phase spectra are analyzed using Spano’s model. It is figured out that the fraction of aggregated chains and the interconnectivity of these domains is fundamental to a high charge carrier mobility. In P3HT layers, such structures can be grown with high-molecular weight, long P3HT chains. Low and medium molecular weight P3HT layers do also contain a significant amount of chain aggregates with high intragrain mobility; however, intergranular connectivity and, therefore, efficient macroscopic charge transport are absent. In P3HT-fullerene blend layers, a highly crystalline morphology that favors the hole transport and the solar cell efficiency can be induced by annealing procedures and the choice of a high-boiling point processing solvent. Based on scanning near-field and polarization optical microscopy, the morphology of oligo-PQT-12 layers is found to be highly crystalline which explains the rather high field-effect mobility in this material as compared to low molecular weight polythiophene fractions. On the other hand, crystalline dislocations and grain boundaries are identified which clearly limit the charge carrier mobility in oligo-PQT-12 layers.
The charge transport properties of organic semiconductors can be widely tuned by molecular doping. Indeed, molecular doping is a key to highly efficient organic light-emitting diodes and solar cells. Despite this vital role, it is still not understood how mobile charge carriers are induced into the bulk semiconductor upon the doping process. This thesis contains a detailed study of the doping mechanism and the electrical properties of P3HT layers which have been p-doped by the strong molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ. The density of doping-induced mobile holes, their mobility, and the electrical conductivity are characterized in a broad range of acceptor concentrations. A long-standing debate on the nature of the charge transfer between P3HT and F4TCNQ is resolved by showing that almost every F4TCNQ acceptor undergoes a full-electron charge transfer with a P3HT site. However, only 5% of these charge transfer pairs can dissociate and induce a mobile hole into P3HT which contributes electrical conduction. Moreover, it is shown that the left-behind F4TCNQ ions broaden the density-of-states distribution for the doping-induced mobile holes, which is due to the longrange Coulomb attraction in the low-permittivity organic semiconductors.Organische Halbleiter kombinieren die molekulare Vielfalt und Anpassbarkeit, die mechanische Flexibilität und die preisgünstige Herstellung und Verarbeitung von Kunststoffen mit fundamentalen Halbleitereigenschaften wie Lichtabsorption und -emission und elektrischer Leitfähigkeit. Unlängst finden organische Leuchtdioden Anwendung in den Displays von TV-Geräten und Smartphones. Für die weitere Entwicklung und den Erfolg organischer Halbleiter ist das Verständnis derer physikalischer Grundlagen unabdingbar. Ein für viele Bauteile fundamentaler Prozess ist der Transport von Ladungsträgern in der organischen Schicht. Die Ladungstransporteigenschaften werden maßgeblich durch die Struktur dieser Schicht bestimmt, z.B. durch den Grad der molekularen Ordnung, die molekulare Verbindung von kristallinen Domänen und durch Defekte der molekularen Packung. Mittels optischer Spektroskopie werden in dieser Arbeit die temperatur-, molekulargewichts- und lösemittelabhängigen Struktureigenschaften poly- und oligothiophenbasierter Schichten untersucht. Dabei basiert die Analyse der Absorptionsspektren auf der Zerlegung in die spezifischen Anteile geordneten und ungeordneten Materials. Es wird gezeigt, dass sich hohe Ladungsträgerbeweglichkeiten dann erreichen lassen, wenn der Anteil der geordneten Bereiche und deren molekulare Verbindung in den Schichten möglichst hoch und die energetische Unordnung in diesen Bereichen möglichst klein ist. Der Ladungstransport in organischen Halbleitern kann außerdem gezielt beeinflusst werden, indem die Ladungsträgerdichte und die elektrische Leitfähigkeit durch molekulares Dotieren, d.h. durch das Einbringen von Elektronenakzeptoren oder -donatoren, eingestellt werden. Obwohl der Einsatz dotierter Schichten essentiell für effiziente Leuchtdioden und Solarzellen ist, ist der Mechanismus, der zur Erzeugung freier Ladungsträger im organischen Halbleiter führt, derzeit unverstanden. In dieser Arbeit wird der Ladungstransfer zwischen dem prototypischen Elektronendonator P3HT und dem Akzeptor F4TCNQ untersucht. Es wird gezeigt, dass, entgegen verbreiteter Vorstellungen, fast alle F4TCNQ-Akzeptoren einen ganzzahligen Ladungstransfer mit P3HT eingehen, aber nur 5% dieser Paare dissoziieren und einen beweglichen Ladungsträger erzeugen, der zur elektrischen Leitfähigkeit beiträgt. Weiterhin wird gezeigt, dass die zurückgelassenen F4TCNQ-Akzeptorionen Fallenzustände für die beweglichen Ladungsträger darstellen und so die Ladungsträgerbeweglichkeit in P3HT bei schwacher Dotierung absinkt. Die elektrischen Kenngrößen Ladungsträgerkonzentration, Beweglichkeit und Leitfähigkeit von F4TCNQ-dotierten P3HT-Schichten werden in dieser Arbeit erstmals in weiten Bereichen verschiedener Akzeptorkonzentrationen untersucht.
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Philipp, Martin. "Electrical Transport and Scattering Mechanisms in Thin Silver Films for Thermally Insulating Glazing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-70920.
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Thin silver films are widely used in low-emissivity coatings for building glazing due to their high reflectance in the infrared and high transmittance in the visible spectrum. The determining parameter for the infrared reflectance is the electrical conductance of the layer stack - the better the conductance the higher the reflectance. Electrically conductive films of thicknesses smaller than the electron mean free path exhibit a strong increase in the residual resistivity proportional to the inverse of the film thickness. Despite intensive discussions, which have extended over tens of years, it is not understood yet if this conductive behavior originates from electron scattering at interfaces (Fuchs-Sondheimer model) or grain boundaries (Mayadas-Shatzkes model). To achieve a fundamental understanding of the prevailing electron scattering mechanisms, aluminum-doped zinc oxide (ZnO:Al) / Ag / ZnO:Al layer stacks produced by magnetron sputtering were investigated concerning their electronic structure and electrical transport properties. The electronic structure of the layer stacks was probed and analyzed by electron energy-loss spectroscopy. By this technique, plasmonic excitations are observed, which can be categorized into excitations of the electrons in the bulk silver and excitations at the ZnO:Al / Ag interface. The plasmons were analyzed with respect to their dispersion and the peak width, and brought into relation with electrical conductivity measurements by calculating the plasmon lifetime and the electron scattering rate. The difficulty in determining the relative contributions of the interface and grain boundary scattering in experimental conditions is due to the fact that the way in which these scattering mechanisms depend on the film thickness, is very similar. Understanding the electron transport in thin films is of paramount importance, because the differentiation between the scattering mechanisms is a key issue for the improvement of the coatings. In the present work, the solution came from the expected difference in the temperature-dependent behavior of the resistivity between electron scattering at interfaces and electron scattering at grain boundaries. Hence, the resistivity was measured as a function of the temperature on layer stacks with different silver film thickness varying in the range of 4 to 200 nm. The data were analyzed using the extended Mayadas-Shatzkes model involving both electron scattering at interfaces (Fuchs-Sondheimer model), and electron scattering at grain boundaries. The results demonstrate that electron scattering at grain boundaries dominates for all film thicknesses. The basic layer stack was compared to more sophisticated systems, obtained either by adding a thin titanium layer in between silver and ZnO:Al, or by exposing the growing silver film to an oxygen partial pressure (oxidizing the film). Furthermore, the effect of annealing at 250°C was studied for all these systemsDünne Silberfilme werden aufgrund ihres hohen Reflexionsvermögens im infraroten Spektrum und ihres hohen Transmissionsvermögens im Spektrum des Sonnenlichtes als Wärmeschutzbeschichtungen für Fensterglas verwendet. Der entscheidende Parameter für das Reflexionsvermögen der Schicht ist die elektrische Leitfähigkeit - je höher die Leitfähigkeit, desto stärker wird Infrarotlicht reflektiert. Elektrisch leitende Schichten mit Schichtdicken dünner als die mittlere freie Weglänge der Elektronen weisen einen starken Anstieg des spezifischen Widerstandes auf, der sich proportional zur inversen Schichtdicke verhält. Trotz ausführlicher Diskussionen während der letzten Jahrzehnte, ist noch nicht geklärt ob dieses Verhalten auf Streuung von Elektronen an Grenzflächen (Fuchs-Sondheimer-Modell) oder an Korngrenzen (Mayadas-Shatzkes-Modell) zurückzuführen ist. Um ein grundlegendes Verständnis der vorherrschenden Streumechanismen zu erlangen, wurden Schichtstapel der Struktur Aluminium-dotiertes Zinkoxid (ZnO:Al) / Ag / ZnO:Al, welche mittels Magnetron-Sputtern hergestellt wurden, hinsichtlich ihrer Transporteigenschaften und elektronischen Struktur untersucht. Die elektronische Struktur der Schichtsysteme ist mittels Elektronen-Energieverlust-Spektroskopie untersucht und bezüglich ihrer plasmonischen Anregungen analysiert wurden. Diese können in Anregungen der Volumenelektronen des Silbers und Anregungen der Elektronen aus der ZnO:Al / Ag Grenzfläche unterteilt werden. Die Plasmonen wurden hinsichtlich ihrer Impulsabhängigkeit und Anregungsbreite analysiert und durch Berechnung der Plasmonenstreurate mit den Messungen der elektrischen Leitfähigkeit verglichen. Aufgund der Tatsache, dass Genzflächen- und Korngrenzstreuung eine ähnliche Schichtdickenabhängigkeit aufweisen, gestaltet sich die Bestimmung der relativen Beiträge beider Streumechanismen als schwierig. Diese Problem kann durch die Untersuchung der Temperaturabhängigkeit der Streumechanismen, die sich für Grenzflächen- und Korngrenzstreuung unterscheidet, gelöst werden. Der spezifische Widerstand wurde in Abhängigkeit von der Temperatur an mehreren Proben unterschiedlicher Silberschichtdicke (im Bereich von 4 bis 200 nm) gemessen. Die Daten wurden anhand des erweiterten Mayadas-Shatzkes-Modells, welches sowohl Streuung an Grenzflächen (Fuchs-Sondheimer-Modell) als auch an Korngrenzen berücksichtigt, evaluiert. Die Ergebnisse zeigen eindeutig, dass für alle Schichtdicken die Elektronenstreuung an Korngenzen der dominierende Streumechanismus ist. Die Ergebnisse der Analyse des fundmentalen Schichtsystems wurden mit denen komplexerer Systeme verglichen, bei denen zum einen durch Hinzufügen einer dünnen Titanschicht die Grenzfläche zwischen Silber und ZnO:Al modifiziert wurde und zum anderen der Silberfilm durch einen erhöhten Sauerstoff-Partialdruck während der Beschichtung oxidiert wurde. Des Weiteren wurde der Effekt einer Temperung bei 250°C an allen Systemen untersucht
Les vitrages bas-émissifs sont fréquemment élaborés par dépôts de revêtements dont la couche active est un film mince d'argent. Le paramètre qui détermine la réflexion dans l'infra-rouge est la conductance électrique de l'empilement. La résistivité électrique résiduelle de films dont l'épaisseur est inférieure au libre parcours moyen des électrons croît fortement en fonction de l'inverse de l'épaisseur. En dépit d'intenses recherches menées pendant des dizaines d'années, l'origine de cet accroissement de résistivité - réflexion des électrons par les interfaces (modèle de Fuchs-Sondheimer) ou par les joints de grains (modèle de Mayadas-Shatzkes). Pour comprendre les mécanismes à l'œuvre dans le transport des électrons, des couches ZnO dopé aluminium (ZnO:Al) / Ag / (ZnO:Al) produites par pulvérisation plasma ont été étudiée concernant leur structure électronique et propriétés de transport électrique. Les empilements ont été examinés par spectroscopie de pertes d'énergie d'électrons. Les spectres font apparaître les excitations des électrons de volume de l'argent et les excitations à l'interface ZnO:Al / Ag. Les excitations ont été analysés concernant leur dispersion. En outre, la durée de vie moyenne des plasmons déterminée d'après la largeur du pic de plasmon d'interface se compare bien à la l'inverse de la fréquence de diffusion des électrons qui se déduit de l'application du modèle de Drude aux données relatives à la résistivité. La difficulté dans la détermination des contributions relatives des modèles de Fuchs-Sondheimer et Mayadas-Shatzkes dans les conditions expérimentales est due au fait que ces deux modèles présentent des variations très similaires en fonction de l'épaisseur des films. D'importance primordiale pour la compréhension du transport dans les films minces, la question est une clé pour l'amélioration des revêtements bas-émissifs. La solution a été apportée ici par la différence de comportement en fonction de la température des diffusions des électrons aux interfaces et aux joints de grains. D'après cela, la résistance d'empilements comportant des films d'argent d'épaisseurs comprises entre 4 et 200 nm a été mesurée en fonction de la température. Les données ont été analysées au moyen de la version du modèle de Mayadas-Shatzkes qui inclut à la fois la diffusion des électrons aux interfaces (modèle de Fuchs-Sondheimer) et la diffusion des électrons aux joints de grains. Il a té démontré que, pour toutes les épaisseurs, la diffusion des électrons aux joints de grains constitue l'effet dominant. Les résultats de l'analyse du système fondamental ont été comparées avec les résultats de systèmes plus sophistiqués, obtenus soit en intercalant une couche additionnelle de titane entre l'argent et le ZnO (méthode communément utilisée pour améliorer le mouillage du ZnO par l'argent), soit par exposition à une pression partielle du film d'argent encours de croissance (pour oxyder le film). En outre, l'effet du recuit à 250°C a été étudié pour tous ces systèmes
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Xu, Hua. "Critical behavior of superconductors and electrical transport properties of carbon nanotube thin films." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7587.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Chen, Yi. "Organic thin film transistors with mono-crystalline rubrene films by horizontal hot wall deposition." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66699.
Full textAbstract:
As promising candidates for future low-cost and flexible display applications, organic thin film transistors (OTFTs) have attracted considerable research interests for the past two decades. Recent advances in organic semiconductor theory and organic film growth/deposition techniques have resulted in OTFTs based on single crystalline organic films with performance approaching or even exceeding the present day's dominant amorphous silicon TFT technology. In this work, efforts have been made to explore suitable methods for the fabrication of thin film transistors based on high mobility organic semiconductors, such as rubrene and pentacene. In the early stage of this work, OTFTs with rubrene single crystals grown by PVT (Physical Vapor Transport) method were fabricated and measured with u-max,eff = 1.07 cm^2/V-s, ION/IOFF ~ 10^5 and VT = 0 V. However, it was noticed that these rubrene films are usually fragile and the adhesion to the substrates is often poor, leading to low reproducibility of functional devices. Hence, direct deposition of organic thin films to the substrates is a necessary measure to solve these problems. In this work, a horizontal hot wall deposition (HHWD) method has been developed to directly deposit high quality rubrene films onto the substrate under low pressure (P ~ 10^-6 torr). The resulted films were continuous with good coverage, however different structural phases from amorphous to near mono-crystalline were present. Through intensive studies on the film morphology and crystallinity of rubrene films deposited under different conditions, it is concluded that various factors can greatly affect the organic thin film growth, including surface treatment conditions, substrate orientations, source evaporation temperatures as well as substrate temperatures. Under the optimal deposition conditions, rubrene films are mono-crystalline with planar structure and grain sizes as large as 0.1 x 2En raison de leur potentiel de pouvoir contribuer à la diminution des coûts dans la fabrication des écrans plats flexibles, les transistors à couche mince organiques (OTFTs) ont attiré énormément d'intérêts dans les dernières décennies.Les avances récentes dans les théories sur les semiconducteurs organiques ainsi que celles sur les techniques de déposition et de croissance ont résulté au développement des OTFTs basés sur des couches organiques monocrystallines avec des performances approchant et même excédant celles dérivées des techniques de fabrication de TFTs de silicium amorphe qui sont couramment dominantes en industrie. Dans cette étude, des efforts ont étés mis pour explorer des méthodes convenables à la fabrication des transistors couches minces basés sur des semiconducteurs organiques à mobilité élevée comme le rubrène et le pentacène.Dans les premières étapes de cette étude, des OTFTs avec du rubrène monocrystalline dont la croissance a été atteinte par la méthode PVT ont été fabriqués et mesurés avec une max,eff = 1.07 cm^2/V-s, un ION/IOFF ~ 10^5 et un VT = 0 V. Il est à noter que ces couches de rubrène sont typiquement fragiles et l'adhésion aux substrats était souvent faible ce qui résultait en une reproductibilité réduite de dispositifs opérationnels. C'est alors que la déposition directe des couches minces organiques aux substrats devient une mesure nécessaire pour résoudre ces problèmes. Dans cette étude, une méthode de déposition à paroi chaude horizontale (HHWD) a été développée pour la déposition directe sous basse pression (P ~ 10^-6 torr)des couches de rubrène à haute qualité sur des substrats. Les couches résultantes sont continues avec une bonne couverture, tandis que des différentes phases structurelles amorphes et monocrystallines sont présentes. Par des études intensives sur la morphologie des couches et$
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Fung, Ka Man. "Injection characteristics of transport layers in PIN OLED." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1448.
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Wu, Mengfei Ph D. Massachusetts Institute of Technology. "Infrared-to-visible upconversion in hybrid thin films of colloidal nanocrystals and organic molecules." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/122872.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018Cataloged from PDF version of thesis.
Includes bibliographical references (pages 152-163).
Photon upconversion is a process where two or more low-energy photons are converted into a single higher-energy photon. Upconversion that turns infrared photons into visible ones is particularly useful, having potential applications in photovoltaics, infrared sensing, and biological imaging. In this thesis, I present a solid-state thin-film device that converts infrared photons with wavelength up to 1.1 [mu]m into visible wavelengths around [lambda] = 610 nm. The device consists of a monolayer of lead sulfide colloidal nanocrystals (NCs) and a thin film of rubrene mixed with emissive DBP molecules. Upconversion is realized via triplet-triplet annihilation (TTA) in rubrene sensitized by the NCs. We demonstrate that compared to the previous all-molecular upconverting systems, the use of inorganic NCs helps extend the excitation wavelength into the infrared and offers simple wavelength tunability.
However, a monolayer of NCs has low infrared absorption, severely limiting the upconversion efficiency and necessitating a high excitation intensity. Here, by adding a silver back reflector with an optical spacer to the device structure, we achieve a five-fold increase in the NC absorption due to optical interference effects and an eleven-fold enhancement in the up-converted output. To extend the idea, we further introduce a distributed Bragg reflector at the front of the device. A resonant microcavity is formed with the NCs placed at the peak of a drastically enhanced optical field. The upconversion efficiency is improved by another order of magnitude, with threshold excitation intensity falling to 13 mW/cm² , which is below the available solar flux. At resonance, the device converts (0.06±0.01)% of incident photons at [lambda] = 980 nm into emitted higher-energy photons. In addition, we improve the upconversion efficiency by shortening the surface ligands on NCs.
With faster triplet transfer, the upconverting device attains higher intrinsic efficiency, converting (7±l)% of the absorbed photons at [lambda] = 808 nm into higher-energy emissive excitons in rubrene. This thesis demonstrates the feasibility of NC-sensitized infrared-to-visible upconversion in solid thin films under low excitation intensities comparable to the solar flux, and paves the way toward the practical utilization of TTA-based upconversion in photovoltaics, imaging, and sensing technologies.
by Mengfei Wu.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Ferlauto, Laura. "Correlation between structural and electrical properties of organic semiconducting materials." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF009/document.
Full textAbstract:
Cette thèse présents plusieurs techniques de caractérisation appliqués à diverses matières organiques dans le but de démêler leur structure-propriétés relation once encapsulés comme matériaux actifs dans les dispositifs de OFET. Un soin particulier est alors dédié aux méthodes de caractérisation structurale (2D-GIXRD, XRR et XRD) à la fois de source de laboratoire classique et de rayonnement de synchrotron. Divers matériaux polymères organiques, compris de p- et n-type de petites molécules et polymères en solution ou déposés par sublimation sous vide sont étudiées. En particulier, l'étude de OFET basée sur deux fonctionnalisés isomères péryléne ne différant que par la forme des alkyle côté chaînes démontre comment la nature ramifié et asymétrique des chaînes peut conduire à une amélioration de la performance électrique avec un simple traitement thermique post-dépôt, tandis que la fabrication de dispositifs ambipolaire polymères au moyen de la technique Langmuir-Schaefer souligne l'importance de la méthode de dépôt sur l'agencement de la matière sur la surface du substrat. Une approche inhabituelle, nommé enquête structurelle in_situ et en temps réel, est aussi présenté pour évaluer les modifications structurelles dans les films minces organiques subissent un processus particulier. Plus précisément, la réponse de la structure des films minces de pentacene à l’application de VSG et VSD au OFET et des films minces dérivés de TTF à la variation d’humidité ont été étudiésThis thesis presents multiple characterization techniques applied to various organic materials with the ultimate goal of unraveling their structure-properties relationship once encapsulated as active materials in OFETs devices. Particular care is then dedicated to the structural characterization methods (2D-GIXRD, XRR and XRD) both from classical laboratory source and from synchrotron radiation. Various organic materials, comprising p- and n-type small molecules and polymers deposited from solution or by vacuum sublimation are investigated. In particular, the study on OFETs based two functionalized perylene isomers differing only in the shape of the alkyl side-chians demonstrates how the branched and asymmetric nature of the chains can lead to an improvement of the electrical performance with a simple post-deposition thermal treatment, while the fabrication of ambipolar polymeric devices by means of Langmir-Schaefer technique highligts the importance of the deposition method on the arrangement of the material on the substrate surface. A more unusual approach, named in-situ and real-time structural investigation, is also presented to evaluate structural modifications in organic thin films undergoing a particular process. Specifically, the structural responce of pentacene thin films to the application of VSG and VSD to the OFET and of TTF derivatives thin films to the variation of humidty were investigated
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Mäklin, J. (Jani). "Electrical and thermal applications of carbon nanotube films." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526203867.
Full textAbstract:
Abstract Carbon nanotubes (CNTs) have fascinating mechanical, electrical and thermal properties, all of which significantly depend on structural properties such as nanotube length, number of walls, lattice defect densities, impurities and surface functional groups. A number of different applications of carbon nanotubes have been demonstrated during the past two decades including electrical interconnects, transistors, heating and cooling devices, sensors and various actuators. However, further studies on the structure-dependent properties and innovative handling techniques of these materials are needed in order to explore the limitations of use and to be able fully to exploit the advantageous properties of such one-dimensional sp2 hybridized carbon nanomaterials. In this thesis, random networks of single-wall and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) and aligned films of multi-walled carbon nanotubes are studied in the context of three main application fields: gas sensing, electrical interconnects/electrodes and thermal cooling elements. Analyses of associated material properties and some feasible integration techniques are discussed. Single-wall and multi-walled carbon nanotube films cast from aqueous dispersions are shown to be selective nitric oxide sensing components in Taguchi-type sensor devices, in which films based on SWCNTs outperformed those made of MWCNTs. The thickness dependent electrical conduction mechanism of inkjet-printed SWCNT films is also discussed. Robust aligned MWCNT films are demonstrated as soft electrical contact brushes in DC motors and in other moving electrical contacts. The thermal properties of freestanding aligned MWCNT forests are analyzed and shown to be potential alternatives to copper or aluminium in the thermal management of electrical componentsTiivistelmä Hiilinanoputkien kiehtovat mekaaniset, sähköiset ja lämmönjohto-ominaisuudet ovat kiinnostaneet tutkijoita suuresti viimeisten kahden vuosikymmenen ajan. Monia erilaisia applikaatioita on demonstroitu tänä aikana: mukaan lukien sähköiset kontaktit, transistori-rakenteet, lämmitys- ja jäähdytyslaitteet, anturirakenteet sekä erilaiset aktuaattori-rakenteet. Tämän väitöskirjan päätavoitteena on tutkia hiilinanoputkien toiminnollisuutta ja käytännöllisyyttä erilaisissa sovelluskohteissa. Tässä työssä käytettävät hiilinanoputkirakenteet ovat joko satunnaisjärjestyksessä olevia nanoputkista koostuvia verkostorakenteita tai yhdensuuntaisia, makroskooppisia hiilinanoputkikalvoja. Nanoputkia tutkitaan kolmessa erityyppisessä sovelluskohteessa: kaasuanturisovelluksessa, sähköisissä kontaktirakenteissa sekä jäähdytyselementteinä. Työssä analysoidaan hiilinanoputkirakenteiden ominaisuuksia eri sovelluskohteissa sekä esitetään joitain käyttökelpoisia tekniikoita hiilinanoputkien integroimiseen olemassa oleviin tekniikoihin. Hiilinanoputkien osoitetaan olevan käyttökelpoisia aktiivisia materiaaleja typpioksidille resistiivisessä kaasuanturirakenteessa. Tulosten perusteella yksiseinämäiset hiilinanoputket ovat moniseinämäisiä herkempiä ja parempia kyseisessä sovelluksessa. Lisäksi tutkitaan ja analysoidaan mustesuihku-tulostettujen yksiseinämäisten hiilinanoputkifilmien sähköisten ominaisuuksien riippuvuutta filmin paksuudesta. Vantterien yhdensuuntaisten moniseinämäisten hiilinanoputkirakenteiden osoitetaan toimivan erinomaisesti pehmeinä sähköisinä kontaktielementteinä liikkuvissa sähköisissä kontakteissa. Vapaasti seisovien yhdensuuntaisten, moniseinämäisten hiilinanoputkirakenteiden lämmönjohto-ominaisuuksien tutkiminen ja analysointi osoittaa, että kyseisiä rakenteita voidaan käyttää tehokkaina jäähdytyselementteinä ja mahdollisesti korvaavana vaihtoehtona alumiinille ja kuparille sähköisten komponenttien lämmönhallinta sovelluksissa
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Zocco, Adam T. "Pentacene-based Organic Thin-film Transistors on Paper." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382950881.
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Gullu, O., S. Ruzgar, S. Asubay, E. Ozerden, T. Kilicoglu, and A. Turut. "Electrical Properties of Al/p-Si Structures with Colchicine Organic Thin Film." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35140.
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In this study, we have fabricated an Al/Colchicine/p-Si structure and have investigated its current–
voltage (I–V) and capacitance–voltage (C–V) characteristics at room temperature. The barrier height and
ideality factor values of 0.68 eV and 3.22, respectively, have been obtained from the I-V plot. The value of
the barrier height was compared with the barrier height value of 0.50 eV of a conventional Al/p-Si diode.
This was attributed to the Colchicine organic film modifying the effective barrier height by affecting the
space charge region of the inorganic Si semiconductor substrate. By using C – 2-V characteristics the diffusion
potential value has been extracted as 1.32 V.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35140
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Gardner, Paul. "Organic matter and size distribution transformations during a simulated bulk phase of sewer transport." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26372.
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As wastewater is transported in a sewer system, in-sewer transformations occur that allow the sewer system to be considered as a pipeline reactor. Domestic wastewater from the local wastewater treatment facility was monitored for a 3 day period to simulate the bulk phase of sewer flow. Aerobic and anoxic reactive environments were studied to determine the change in organic matter and size distribution. Aerobic and anoxic conditions showed similar treatment of organic matter with an average of 55% of the total chemical oxygen demand (CODt) removed in 72 hours. The CODt consumption rate increased to a mean maximum of 8.4 mg/L/h a mean experiment time of 24 hours. The majority of the organic removal occurred in the first 42 hours. Aerobic conditions led to the formation of larger microbial flocs than anoxic conditions demonstrated by an increasing trend of mean area particle diameter (D a) with the mean increase 8 microns compared to a 3 micron decrease for anoxic conditions. Initial substrate and biomass quality strongly influenced the observed transformations.
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Chan, Yiu Him. "Effect of dopants and gate dielectrics on charge transport and performance of organic thin film transistor." HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1450.
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Strunk, Karl-Philipp [Verfasser], and Christian [Akademischer Betreuer] Melzer. "Charge Carrier Transport in Solution Processed Organic Semiconductor Thin Films / Karl-Philipp Strunk ; Betreuer: Christian Melzer." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/1195143788/34.
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FERLAUTO, Laura. "CORRELATION BETWEEN STRUCTURAL AND ELECTRICAL PROPERTIES OF ORGANIC SEMICONDUCTING MATERIALS." Doctoral thesis, Università degli studi di Ferrara, 2015. http://hdl.handle.net/11392/2389073.
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Grande, Silvia. "Electrical spectroscopy of rubrene bulk and thin film crystals." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6678/.
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One of the most diffused electronic device is the field effect transistor (FET), contained in number of billions in each electronic device. Organic optoelectronics is an emerging field that exploits the unique properties of conjugated organic materials to develop new applications that require a combination of performance, low cost and processability. Organic single crystals are the material with best performances and purity among the variety of different form of organic semiconductors. This thesis is focused on electrical and optical characterization of Rubrene single crystal bulk and thin films. Rubrene bulk is well known but for the first time we studied thin films. The first Current-voltage characterization has been performed for the first time on three Rubrene thin films with three different thickness to extract the charge carriers mobility and to assess its crystalline structure. As results we see that mobility increase with thickness.
Field effect transistor based on Rubrene thin films on $SiO_2$ have been characterize by current-voltage (I-V) analyses (at several temperatures) and reveals a hopping conduction. Hopping behavior probably is due to the lattice mismatch with the substrate or intrinsic defectivity of the thin films. To understand effects of contact resistance we tested thin films with the Transmission Line Method (TLM) method. The TLM method revealeds that contact resistance is negligible but evidenced a Schottky behavior in a limited but well determined range of T. To avoid this effect we carried out annealing treatment after the electrode evaporation iswe performed a compete I-V characterization as a function of in temperature to extract the electronic density of states (DOS) distribution through the Space Charge Limited Current (SCLC) method. The results show a DOS with an exponential trenddistribution, as expected. The measured mobility of thin films is about 0.1cm^2/Vs and it increases with the film thickness. Further studies are necessary to investigate the reason and improve performances. From photocurrent spectrum we calculated an Eg of about 2.2eV and both thin films and bulk have a good crystal order. Further measurement are necessary to solve some open problems
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Effertz, Christian [Verfasser]. "Organic molecular crystals: from thin-films to devices : investigation of thin-film formation and electronic transport properties of polycrystalline perylene films / Christian Effertz." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018191550/34.
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Campbell, Duncan. "A study of the optical absorption and electrical conductivity of lead phthalocyanine with regard to its viability as a means of sensing nitrogen dioxide." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360641.
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Möllmann, Alexander [Verfasser]. "Nanostructured Metal Oxide Thin Films as Electron Transport Material for Inorganic-Organic Hybrid Perovskite Solar Cells / Alexander Möllmann." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219478067/34.
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Shihub, Salahedin Ibrahim. "Studies of the electrical and structural properties of organic semiconducting thin films of thermally evaporated cobalt phthalocyanine." Thesis, Keele University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301164.
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Andersson, Peter. "Charge Transport Modulation and Optical Absorption Switching in Organic Electronic Devices." Doctoral thesis, Norrköping : Department of Science and Technology, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10271.
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Kneiß, Max, Marcus Jenderka, Kerstin Brachwitz, Michael Lorenz, and Marius Grundmann. "Modeling the electrical transport in epitaxial undoped and Ni-, Cr-, and W-doped TiO2 anatase thin films." American Institute of Physics, 2014. https://ul.qucosa.de/id/qucosa%3A31223.
Full textAbstract:
Electrical transport in undoped and Ni-, Cr-, and W-doped TiO2 thin films on SrTiO3(001) is modelled
either with the sum of two thermally activated processes with exponential temperature dependence
of conductivity, or with the sum of three-dimensional Mott variable-range hopping
(VRH) and an activated process with low activation energy. The latter is interpreted for both models
as small polaron hopping (<θD/4). According to reduced chi-square values, the double activated
model is superior for data of higher ordered films grown at 540 and 460 °C. For lower growth temperature,
VRH plus activated conductivity fits partly better. For all dopants, n-type conductivity is
observed.
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Pingel, Patrick [Verfasser], and Dieter [Akademischer Betreuer] Neher. "Morphology, charge transport properties, and molecular doping of thiophene-based organic semiconducting thin films / Patrick Pingel. Betreuer: Dieter Neher." Potsdam : Universitätsbibliothek der Universität Potsdam, 2014. http://d-nb.info/1049328426/34.
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Adams, Michael [Verfasser], and B. S. [Akademischer Betreuer] Richards. "Triplet Exciton Transport in Porphyrin-Based Surface-Anchored Metal-Organic Framework Thin Films / Michael Adams ; Betreuer: B. S. Richards." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/119237360X/34.
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MORGANO, MANUEL. "Electrical and optical characterization of nanostructured silicon-rich oxide films for advanced photovoltaic applications." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28478.
Full textAbstract:
In this thesis a through study of nanostructured silicon rich oxide for advanced photovoltaic application is carried forward. Several structural parameters are studied, among which are: thickness, nanostructuration, stoichiometry, doping. Along with these, the effect of light is studied and an EQE measurements on an all silicon quantum dot based solar cell is presented.
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RESTREPO, JUAN HUMBERTO SERNA. "THIN FILMS OF ORGANIC MOLECULAR SYSTEMS: STUDY OF INFLUENCE OF THE DEPOSITION METHODS ON OPTICAL AND ELECTRICAL PROPERTIES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18798@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONeste trabalho é apresentado um estudo da influência das técnicas de deposição de filmes finos nas propriedades físicas de dois sistemas moleculares orgânicos. O estudo foi realizado através da análise das características ópticas e elétricas de filmes finos e dispositivos OLEDs crescidos utilizando os sistemas orgânicos: (1) DCM2:Alq3 e (2) [Sm(tta)3(dppmo):Eu(tta)3(dppmo)]. Em ambos os casos um material é utilizado como matriz (Alq3 ou complexo de Sm3+) e outro como dopante (DCM2 ou complexo de Eu3+). A análise das propriedades físicas do sistema (1), crescido por co-deposição térmica e por spin-coating, permitiram mostrar que a resposta do sistema muda em função da técnica de deposição usada. Por exemplo, o processo de transferência de energia molecular entre a matriz (Alq3) e o dopante (DCM2) varia de uma técnica para outra, sendo menos eficiente na técnica onde o filme crescido permite obter uma separação maior entre as moléculas. O estudo também mostrou que a transferência de energia pode ser inibida por meio de um processo de fotodegradação do sistema com luz UV. A análise do sistema (2), crescido pelas técnicas de co-deposição térmica e deposição térmica de moléculas misturadas na fase sólida, mostrou que a resposta deste sistema é independente do método de deposição utilizado. Além disso, a dopagem da matriz Sm(tta)3(dppmo) com um complexo de európio que possui os mesmos ligantes orgânicos, permitiu observar uma transferência de energia intermolecular entre os dois complexos, assim como um aumento da intensidade de emissão de algumas das transições do íon Eu3+. Estes sistemas foram usados na fabricação de dispositivos orgânicos eletroluminescentes e o sistema molecular 1 como sensor de radiação UV.
This dissertation reports the study of the influence of different deposition techniques on the physical properties of two molecular organic systems: (1) DCM2:Alq3 e (2) [Sm(tta)3(dppmo):Eu(tta)3(dppmo)]. The investigation was carried out by analyzing the optical and electrical characteristics of thin films and organic light-emitting devices (OLEDs) based on the two organic systems. In both systems, one of the compounds was used as the host (Alq3 and Sm-based complex) and the other as the dopant (DCM2 and Eu-based complex). Analysis of the system (1) physical properties, showed that the system response varies as a function of the used deposition technique (in this case, thermal codeposition and spin-coating). For example, the molecular energy-transfer process between the matrix (Alq3) and the dopant (DCM2) varies from one technique to the other, being less efficient in the one where the molecular separation is larger. The study also demonstrated that the energy transfer can be inhibited by means of UV photodegradation process. System (2) was grown by thermal codeposition as well as thermal deposition of molecules mixed in solid phase. In this case, the results indicated that the response of this system is independent of the deposition technique chosen. Besides, doping the Sm(tta)3(dppmo) host with an europium complex allowed to observe not only an intermolecular energytransfer between the two complexes but also an increasing in the emission intensity of some Eu3+ transitions. Both systems can be applied to UV radiation sensors’ fabrication and organic light-emitting devices.
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Chang, Mincheol. "Processing parameter effects on the molecular ordering and charge transport of poly(3-hexylthiophene) thin films." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54281.
Full textAbstract:
Conjugated polymers have attracted much interest as promising alternatives to inorganic semiconductors, due to their low-temperature, solution-based processability, which may provide for low-cost, large-area electronic device fabrication. However, commercialization of polymer-based electronic devices has been restricted owing to low device performance of solidified thin-films. In order to enhance charge transport of polymer semiconductor thin-films, the self-organization of organic polymer semiconductors into ordered supramolecular assemblies has been achieved by tuning a range of process parameters including film deposition method (spin vs. drop cast), solvent boiling point (low vs. high boiling point), polymer-dielectric interface treatment, and post-deposition processing (solvent vapor or thermal annealing). However, these strategies give rise to limitations for large-scale high-throughput processing due to associated pre- and/or post semiconductor deposition steps.
Therefore, in this thesis, we identify alternative processing parameters (i.e., hydrogen bonds between good and poor solvents, UV irradiation to polymer precursor solutions, and combination of sonication and subsequent UV irradiation to polymer precursor solutions) which can contribute to enhancement in charge transport of a model polymer semiconductor, poly(3-hexylthiophene) (P3HT), eliminating the additional pre- and/or post-steps mentioned above. Further, we understand of how the processing parameters effect intra- and intermolecular interactions of the polymer chains, micro- through macroscopic morphologies, and charge transport characteristics of the resultant films.
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Bange, Sebastian. "Transient optical and electrical effects in polymeric semiconductors." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3631/.
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Classical semiconductor physics has been continuously improving electronic
components such as diodes, light-emitting diodes, solar cells and transistors
based on highly purified inorganic crystals over the past decades. Organic
semiconductors, notably polymeric, are a comparatively young field of
research, the first light-emitting diode based on conjugated polymers having
been demonstrated in 1990. Polymeric semiconductors are of tremendous interest
for high-volume, low-cost manufacturing ("printed electronics"). Due to
their rather simple device structure mostly comprising only one or two
functional layers, polymeric diodes are much more difficult to optimize
compared to small-molecular organic devices. Usually, functions such as charge
injection and transport are handled by the same material which thus needs to
be highly optimized. The present work contributes to expanding the knowledge
on the physical mechanisms determining device performance by analyzing the
role of charge injection and transport on device efficiency for blue and
white-emitting devices, based on commercially relevant spiro-linked
polyfluorene derivatives. It is shown that such polymers can act as very
efficient electron conductors and that interface effects such as charge
trapping play the key role in determining the overall device efficiency. This work contributes to the knowledge of how charges drift through the polymer
layer to finally find neutral emissive trap states and thus allows a
quantitative prediction of the emission color of multichromophoric systems,
compatible with the observed color shifts upon driving voltage and temperature
variation as well as with electrical conditioning effects. In a more
methodically oriented part, it is demonstrated that the transient device
emission observed upon terminating the driving voltage can be used to monitor
the decay of geminately-bound species as well as to determine trapped charge
densities. This enables direct comparisons with numerical simulations based on
the known properties of charge injection, transport and recombination. The
method of charge extraction under linear increasing voltages (CELIV) is
investigated in some detail, correcting for errors in the published approach
and highlighting the role of non-idealized conditions typically present in
experiments. An improved method is suggested to determine the field dependence
of charge mobility in a more accurate way. Finally, it is shown that the
neglect of charge recombination has led to a misunderstanding of experimental
results in terms of a time-dependent mobility relaxation.Klassische Halbleiterphysik beschäftigt sich bereits seit mehreren Jahrzehnten erfolgreich mit der Weiterentwicklung elektronischer Bauteile wie Dioden, Leuchtdioden, Solarzellen und Transistoren auf der Basis von hochreinen anorganischen Kristallstrukturen. Im Gegensatz hierzu ist das Forschungsgebiet der organischen, insbesondere der polymeren Halbleiter noch recht jung: Die erste Leuchtdiode auf der Basis von "leitfähigem Plastik" wurde erst 1990 demonstriert. Polymere Halbleiter sind hierbei von besonderem Interesse für hochvolumige Anwendungen im Beleuchtungsbereich, da sie sich kostengünstig herstellen und verarbeiten lassen ("gedruckte Elektronik"). Die vereinfachte Herstellung bedingt dabei eine vergleichsweise geringe Komplexität der Bauteilstruktur und verringert die Optimierungsmöglichkeiten. Die vorliegende Arbeit leistet einen Beitrag zum Verständnis der Vorgänge an Grenzflächen und im Volumen von polymeren Leuchtdioden und ermöglicht damit ein besseres Verständnis der Bauteilfunktion. Im Fokus steht hierbei mit einem spiro-verknüpften Polyfluorenderivat ein kommerziell relevanter Polymertyp, der amorphe und hochgradig temperaturstabile Halbleiterschichten bildet. Ausgehend von einer Charakterisierung der Ladungstransporteigenschaften wird im Zusammenspiel mit numerischen Simulationen der Bauteilemission gezeigt, welche Rolle die polymeren und metallenen Kontaktelektroden für die Bauteilfunktion und -effizienz spielen. Des Weiteren wird ein weiß-emittierendes Polymer untersucht, bei dem die Mischung von blauen, grünen und roten Farbstoffen die Emissionsfarbe bestimmt. Hierbei wird das komplexe Wechselspiel aus Energieübertrag zwischen den Farbstoffen und direktem Ladungseinfang aufgeklärt. Es wird ein quantitatives Modell entwickelt, das die beobachtete Verschiebung der Emissionsfarbe unter wechselnden elektrischen Betriebsparametern erklärt und zusätzlich die Vorhersage von Temperatur- und elektrischen Konditionierungseffekten ermöglicht. Ausgehend von leicht messbaren Parametern wie Stromstärken und Emissionsspektren ermöglicht es Rückschlüsse auf mikroskopische Vorgänge wie die Diffusion von Ladungen hin zu Farbstoffen. Es wird gezeigt, dass im Gegensatz zu bisherigen Erkenntnissen der Ladungseinfang durch Drift im elektrischen Feld gegenüber der Diffusion überwiegt. In einem eher methodisch orientierten Teil zeigt die Arbeit, wie die beim Abschalten von Leuchtdioden beobachtbare Emission dazu verwendet werden kann, Erkenntnisse zu Ladungsdichten während der Betriebsphase zu gewinnen. Es wird abschließend nachgewiesen, dass eine gängige Methode zur Bestimmung von Ladungsbeweglichkeiten unter typischen Messbedingungen fehlerbehaftet ist. Ergebnisse, die bisher als eine zeitliche Relaxation der Beweglichkeit in ungeordneten Halbleitern interpretiert wurden, können damit auf die Rekombination von Ladungen während der Messung zurückgeführt werden. Es wird außerdem gezeigt, dass eine Modifikation der bei der Auswertung verwendeten Analytik die genauere Vermessung der Feldstärkeabhängigkeit der Beweglichkeit ermöglicht.
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Scaini, Denis. "Electrical characterization of organic monolayers at the nanoscale: a differential scanning conductive tip AFM investigation." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2609.
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2006/2007CT-AFM (Conductive Tip AFM) is commonly used for electrical characterization of organic and inorganic surface systems. Understanding electron transfer at the molecular level may lead to the development of molecular assemblies with unique properties and is of great importance for the advancement of both organic, molecular and bio-electronics. In this work we follow an approach to the study of Metal-molecule-Metal surface junctions that uses a combination of different AFM-based techniques. We first use nanografting to build nanopatches of the molecules of interest into a hosting reference self assembled monolayer (SAM) typically made of alkane and aromatic thiols. After the tip is changed to a conductive one, CT-AFM is used to characterize electrically the whole system recording, at the same time, the system topography. Some of the advantages of this approach are the possibility to build and study a wide range of different monolayers side-by-side on the same sample and the in-situ control of the quality both of the hosting monolayer and that of the grafted patches. Results will be presented on saturated and unsaturated thiols self-assembled and nanografted on Au(111) surfaces. We will also show a clear correlation between the contrast in current images and the quality of molecular packing inside the nanopatches.
XX Ciclo
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Sugiura, Kenji, Hiromichi Ohta, Shin-ichi Nakagawa, Rong Huang, Yuichi Ikuhara, Kenji Nomura, Hideo Hosono, and Kunihito Koumoto. "Anisotropic carrier transport properties in layered cobaltate epitaxial films grown by reactive solid-phase epitaxy." American Institite of Physics, 2009. http://hdl.handle.net/2237/12628.
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