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1
Ali, Alaa Y., Natalie P. Holmes, Nathan Cooling, John Holdsworth, Warwick Belcher, Paul Dastoor, and Xiaojing Zhou. "Optimization of Bulk Heterojunction Organic Photovoltaics." Coatings 13, no. 7 (July 24, 2023): 1293. http://dx.doi.org/10.3390/coatings13071293.
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The performance of poly(3-hexylthiophene) (P3HT): phenyl-C61-butyric acid methyl ester (PCBM) organic photovoltaic (OPV) devices was found to be strongly influenced by environmental during preparation, thermal annealing conditions, and the material blend composition. We optimized laboratory fabricated devices for these variables. Humidity during the fabrication process can cause electrode oxidation and photo-oxidation in the active layer of the OPV. Thermal annealing of the device structure modifies the morphology of the active layer, resulting in changes in material domain sizes and percolation pathways which can enhance the performance of devices. Thermal annealing of the blended organic materials in the active layer also leads to the growth of crystalline for P3HT domains due to a more arrangement packing of chains in the polymer. Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) acts as a hole transport layer in these P3HT:PCBM devices. Two commercially materials of PEDOT:PSS were utilizing in the optimization of the OPV in this research; high conductivity PEDOT:PSS-PH1000 and PEDOT:PSS-Al4083, which is specifically designed for OPV interfaces. It was demonstrated that OPVs were prepared with PEDOT:PSS-PH1000 have a less than the average performance of PEDOT:PSS-Al4083. The power conversion efficiency (PCE) decreased clearly with a reducing in masking area devices from 5 mm2 to 3.8 mm2 for OPVs based on PH1000 almost absolutely due to the reduced short circuit current (Jsc). This work provides a roadmap to understanding P3HT:PCBM OPV performance and outlines the preparation issues which need to be resolved for efficient device fabrication
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Kim, Jihee, Chang Woo Koh, Mohammad Afsar Uddin, Ka Yeon Ryu, Song-Rim Jang, Han Young Woo, Bogyu Lim, and Kyungkon Kim. "Improving the Photostability of Small-Molecule-Based Organic Photovoltaics by Providing a Charge Percolation Pathway of Crystalline Conjugated Polymer." Polymers 12, no. 11 (November 5, 2020): 2598. http://dx.doi.org/10.3390/polym12112598.
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Photostability of small-molecule (SM)-based organic photovoltaics (SM-OPVs) is greatly improved by utilizing a ternary photo-active layer incorporating a small amount of a conjugated polymer (CP). Semi-crystalline poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)] (PPDT2FBT) and amorphous poly[(2,5-bis(2-decyltetradecyloxy)phenylene)-alt-(5,6-dicyano-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole)] (PPDT2CNBT) with similar chemical structures were used for preparing SM:fullerene:CP ternary photo-active layers. The power conversion efficiency (PCE) of the ternary device with PPDT2FBT (Ternary-F) was higher than those of the ternary device with PPDT2CNBT (Ternary-CN) and a binary SM-OPV device (Binary) by 15% and 17%, respectively. The photostability of the SM-OPV was considerably improved by the addition of the crystalline CP, PPDT2FBT. Ternary-F retained 76% of its initial PCE after 1500 h of light soaking, whereas Ternary-CN and Binary retained only 38% and 17% of their initial PCEs, respectively. The electrical and morphological analyses of the SM-OPV devices revealed that the addition of the semi-crystalline CP led to the formation of percolation pathways for charge transport without disturbing the optimized bulk heterojunction morphology. The CP also suppressed trap-assisted recombination and enhanced the hole mobility in Ternary-F. The percolation pathways enabled the hole mobility of Ternary-F to remain constant during the light-soaking test. The photostability of Ternary-CN did not improve because the addition of the amorphous CP inhibited the formation of ordered SM domains.
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Bhargava, Udayagiri R. "A Brief Review on Dye Sensitized Solar Cells." International Journal for Research in Applied Science and Engineering Technology 9, no. VII (July 31, 2021): 3289–98. http://dx.doi.org/10.22214/ijraset.2021.37089.
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Photo-voltaic (PV) devices such as a Dye-Sensitized Solar Cell (DSSC) is a source of energy that converts incident photon or solar radiation to usable electricity. DSSCs are fast becoming a viable and interesting alternative to the traditional inorganic photo-voltaic devices to address the demerits of the inorganic PV devices like the use of expensive noble metals and high-cost chemical synthesis processes. A DSSC functions with two main components, i.e., a photo-sensitizer that absorbs incident light and a semiconductor onto which it is adhered to and a conductive glass housing such as Florine-doped Tin Oxide (FTO) or Indium-doped Tin Oxide (ITO), between which the sensitizer, semiconductor and an electrolyte are sandwiched. The semiconductor is preferably a wide-band semiconductor, of which the commonly used semiconductors in a DSSC are made of a nanoparticle layer of Titanium dioxide (TiO2), Zinc oxide (ZnO) and Tin oxide (SnO2). The utility of these solar cells with a diverse number of natural photo-sensitizers for use as an alternative PV device is described. Currently, there are an abundance of natural sources that could be used to obtain photo-sensitizers from, such as, micro and macro algae, plants, bacteria, etc. leading to increased importance in renewable energy sector and has gained traction to be a viable renewable energy resource. In addition to the functioning of an organic DSSC, various characteristics of the pigments used as photo-sensitizers are described here. Patents filed regarding eco-friendly and natural Dye-Sensitized Solar Cells have been increasing as of late and holds substantial promise.
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Bonasera, Aurelio, Giuliana Giuliano, Giuseppe Arrabito, and Bruno Pignataro. "Tackling Performance Challenges in Organic Photovoltaics: An Overview about Compatibilizers." Molecules 25, no. 9 (May 8, 2020): 2200. http://dx.doi.org/10.3390/molecules25092200.
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Organic Photovoltaics (OPVs) based on Bulk Heterojunction (BHJ) blends are a mature technology. Having started their intensive development two decades ago, their low cost, processability and flexibility rapidly funneled the interest of the scientific community, searching for new solutions to expand solar photovoltaics market and promote sustainable development. However, their robust implementation is hampered by some issues, concerning the choice of the donor/acceptor materials, the device thermal/photo-stability, and, last but not least, their morphology. Indeed, the morphological profile of BHJs has a strong impact over charge generation, collection, and recombination processes; control over nano/microstructural morphology would be desirable, aiming at finely tuning the device performance and overcoming those previously mentioned critical issues. The employ of compatibilizers has emerged as a promising, economically sustainable, and widely applicable approach for the donor/acceptor interface (D/A-I) optimization. Thus, improvements in the global performance of the devices can be achieved without making use of more complex architectures. Even though several materials have been deeply documented and reported as effective compatibilizing agents, scientific reports are quite fragmentary. Here we would like to offer a panoramic overview of the literature on compatibilizers, focusing on the progression documented in the last decade.
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Tian, Hongyue, Mingxin Zhao, Xiaoling Ma, Chunyu Xu, Wenjing Xu, Zhongyuan Liu, Miao Zhang, and Fujun Zhang. "Critical Progress of Polymer Solar Cells with a Power Conversion Efficiency over 18%." Energies 16, no. 11 (June 2, 2023): 4494. http://dx.doi.org/10.3390/en16114494.
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The power conversion efficiencies (PCEs) of organic photovoltaics (OPVs) have reached more than 19%, along with the prosperous development of materials and device engineering. It is meaningful to make a comprehensive review of the research of OPVs for further performance improvement. In this review, some typical materials of high-performance OPVs are summarized, including representative polymer donor materials, non-fullerene acceptor materials, and interfacial modification materials, as well as their design rules for molecular engineering. From the point of view of device engineering, active layer treatment and deposition technology are introduced, which can play a critical role in adjusting the degree of molecular aggregation and vertical distribution. Meanwhile, a ternary strategy has been confirmed as an efficient method for improving the performance of OPVs, and the multiple roles of the appropriate third component in the photo-electronic conversion process are emphasized and analyzed. The challenges and perspectives concerning this region are also put forward for further developing high-performance OPVs.
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Sreekala, C. O., P. F. Saneesh, K. S. Sreelatha, A. Kishnashree, and M. S. Roy. "Organic Bulk Heterojunction Solar Cell Based on Rosebengal: ncTiO2 and Parameter Extraction by Simulation." Advanced Materials Research 403-408 (November 2011): 4304–10. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.4304.
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In bulk heterojunction solar cells, the donor and acceptor materials are intimately blended throughout the bulk, so that the excitons generated will reach the interface within their lifetime. In this work, Rosebengal (RB) is used as the donor material and nanocrystalline Titanium dioxide (nc TiO2) as the acceptor material. Devices with device structure ITO/RB:TiO2/Ag are prepared and their optical and electrical properties are compared at different temperatures. Optical absorption spectroscopic analysis shows that the absorption of Rose bengal ranges from 650-800 nm corresponding to a band gap of 1.98 eV. Cyclic voltametric analysis, and photo voltaic properties are analysed. Using simulation, the dark current parameters such as ideality factor (n), mobility (µ) potential barrier (φb) and carrier concentration are extracted and tabulated.
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Channa, Iftikhar Ahmed, Ali Dad Chandio, Muhammad Rizwan, Aqeel Ahmed Shah, Jahanzeb Bhatti, Abdul Karim Shah, Fayaz Hussain, Muhammad Ali Shar, and Abdulaziz AlHazaa. "Solution Processed PVB/Mica Flake Coatings for the Encapsulation of Organic Solar Cells." Materials 14, no. 10 (May 12, 2021): 2496. http://dx.doi.org/10.3390/ma14102496.
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Organic photovoltaics (OPVs) die due to their interactions with environmental gases, i.e., moisture and oxygen, the latter being the most dangerous, especially under illumination, due to the fact that most of the active layers used in OPVs are extremely sensitive to oxygen. In this work we demonstrate solution-based effective barrier coatings based on composite of poly(vinyl butyral) (PVB) and mica flakes for the protection of poly (3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) against photobleaching under illumination conditions. In the first step we developed a protective layer with cost effective and environmentally friendly methods and optimized its properties in terms of transparency, barrier improvement factor, and bendability. The developed protective layer maintained a high transparency in the visible region and improved oxygen and moisture barrier quality by the factor of ~7. The resultant protective layers showed ultra-flexibility, as no significant degradation in protective characteristics were observed after 10 K bending cycles. In the second step, a PVB/mica composite layer was applied on top of the P3HT film and subjected to photo-degradation. The P3HT films coated with PVB/mica composite showed improved stability under constant light irradiation and exhibited a loss of <20% of the initial optical density over the period of 150 h. Finally, optimized barrier layers were used as encapsulation for organic solar cell (OSC) devices. The lifetime results confirmed that the stability of the OSCs was extended from few hours to over 240 h in a sun test (65 °C, ambient RH%) which corresponds to an enhanced lifetime by a factor of 9 compared to devices encapsulated with pristine PVB.
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Debesay, Thomas H., and Sam-Shajing Sun. "Phototransistors Based on A Lightly Doped P3HT." MRS Advances 5, no. 37-38 (2020): 1975–82. http://dx.doi.org/10.1557/adv.2020.306.
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AbstractOrganic/Polymeric Semiconductor (OSC) based devices have been under extensive study for the past three decades due to their intrinsic potential advantages such as lightweight, mechanical flexibility, biocompatibility, low toxicity, abundant material availability, low cost of processing, etc. A phototransistor incorporates the properties and functions of a transistor and photodetector. In this study, a phototransistor based on a donor/acceptor (D/A) pair (photo-doping) was studied and demonstrated. Unlike in organic photovoltaics (OPV) where 1:1 proportion by mass of the donor:acceptor is utilized to make up the active layer, that ratio appears to be too high for phototransistor applications. According to literature, this 1:1 concentration leads to low overall device performance, lack of I-V curve saturation (kink effect), and bipolar behavior. By altering fabrication techniques and doping concentrations, we were able to demonstrate a donor/acceptor based phototransistor with p-type characteristics with improved performance. In this work, we fabricated a high-performance OFET based on a very small amount of Phenyl-C71-butyric acid methyl ester (PCBM) doped into a Poly(3-hexylthiophene) (P3HT) host. With this work, a greater understanding behind the optimization of D/A based phototransistors is advanced.
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Roy, Palas, and Jyotishman Dasgupta. "Temporal probing of excitons in organic semiconductors." Pure and Applied Chemistry 92, no. 5 (May 26, 2020): 707–16. http://dx.doi.org/10.1515/pac-2018-1230.
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AbstractPhotoinduced charge generation forms the physical basis for energy conversion in organic photovoltaic (OPV) technology. The fundamental initial steps involved are absorption of light by organic semiconductors (generally π-conjugated polymers) to generate photoexcited states (Frenkel excitons) followed by charge transfer and charge separation processes in presence of suitable acceptor. The absorbed photon energy must be utilized completely for achieving maximum device efficiency. However progressive relaxation losses of instantaneously generated high-energy or hot-excited states form major bottleneck for maximum derivable voltage. This efficiency limiting factor has been challenged recently by the role of hot-carriers in efficient generation of charges. Therefore tailoring the dissociation of hot-exciton to be temporally faster than all relaxation processes could minimize the energy loss pathways. Implementation of this concept of hot-carrier photovoltaics demands critical understanding of molecular parameters that circumvent all energy relaxation processes and favor hot-carrier generation. In my dissertation work, I have examined the fate of photo-generated excitons in the context of polymer backbone and morphology, and therefore obtain a fundamental structure-function correlation in organic semiconductors.
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Ali, Alaa Y., Natalie P. Holmes, Mohsen Ameri, Krishna Feron, Mahir N. Thameel, Matthew G. Barr, Adam Fahy, et al. "Low-Temperature CVD-Grown Graphene Thin Films as Transparent Electrode for Organic Photovoltaics." Coatings 12, no. 5 (May 16, 2022): 681. http://dx.doi.org/10.3390/coatings12050681.
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Good conductivity, suitable transparency and uniform layers of graphene thin film can be produced by chemical vapour deposition (CVD) at low temperature and utilised as a transparent electrode in organic photovoltaics. Using chlorobenzene trapped in poly(methyl methacrylate) (PMMA) polymer as the carbon source, growth temperature (Tgrowth) of 600 °C at hydrogen (H2) flow of 75 standard cubic centimetres per minute (sccm) was used to prepare graphene by CVD catalytically on copper (Cu) foil substrates. Through the Tgrowth of 600 °C, we observed and identified the quality of the graphene films, as characterised by Raman spectroscopy. Finally, P3HT (poly (3-hexylthiophene-2, 5-diyl)): PCBM (phenyl-C61-butyric acid methyl ester) bulk heterojunction solar cells were fabricated on graphene-based window electrodes and compared with indium tin oxide (ITO)-based devices. It is interesting to observe that the OPV performance is improved more than 5 fold with increasing illuminated areas, hinting that high resistance between graphene domains can be alleviated by photo generated charges.
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Liu, Yong, Wei-Guo Liu, Da-Bin Lin, Xiao-Ling Niu, Shun Zhou, Jin Zhang, Shao-Bo Ge, Ye-Chuan Zhu, Xiao Meng, and Zhi-Li Chen. "Fabrication and Optical Properties of Transparent P(VDF-TrFE) Ultrathin Films." Nanomaterials 12, no. 4 (February 9, 2022): 588. http://dx.doi.org/10.3390/nano12040588.
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The films of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) are widely used in piezoelectric tactile sensors, vibration energy harvesters, optical frequency conversion materials and organic photo-voltaic devices because of high electroactive, good optical and nonlinear optical properties, respectively. In this work, the multilayer structured ultrathin films were fabricated by the Langmuir–Blodgett technique, and the thickness per layer can be controlled accurately. It was found that as the collapse pressure of P(VDF-TrFE) (25:75) and the optimal dipping value are 60~70 mN/m and 15 mN/m, respectively, a high-density film can be obtained due to the compression of molecules. The surface topography and optical properties of the LB films were characterized by X-ray diffraction, white light interferometer and variable-angle spectrum ellipsometer. It was observed that the films are transparent in the visible region and IR-band, but show a high absorption in the UV band. Besides, the transmittance of the films ranges from 50% to 85% in the visible region, and it linearly decreases with the number of monolayers. The average thickness of per deposition layer is 2.447 nm, 2.688 nm and 2.072 nm, respectively, under three measurement methods. The calculated refractive index ranged from 1.443 to 1.598 (600~650 nm) by the Cauchy-model.
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Ohta, Kaoru, Mitsuharu Suzuki, Hiroko Yamada, and Keisuke Tominaga. "(Invited) Probing Charge Carrier Dynamics in Porphyrin-Based Bulk Heterojunction Thin Films with Time-Resolved Terahertz Spectroscopy." ECS Meeting Abstracts MA2022-01, no. 13 (July 7, 2022): 909. http://dx.doi.org/10.1149/ma2022-0113909mtgabs.
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Organic photovoltaic (OPV) solar cells have attracted much attention in recent years because of the low production cost and ease of device fabrication. However, the power conversion efficiency is still low compared to the silicon and perovskite solar cells so that further research is necessary to improve their performance. In particular, understanding of the detailed mechanisms of charge carrier generation, recombination and carrier transport process is very important for developing design principles of new compounds for OPVs. Until now, polymer-based compounds have been widely used for p-type semiconductors. However, it is not easy to obtain information on how the microscopic structure of bulk heterojunction (BHJ) blend of donor and acceptor materials affect the charge carrier dynamics because one cannot easily control the molecular weight and conformational distributions of polymer compounds. On the other hand, small molecule-based semiconductors have several unique advantages such well-defined chemical structures, ease of purification and small batch-to-batch variations. Tetrabenzoporphyrin (BP) has been frequently used as a small-molecule organic semiconductor. Recently, Yamada and coworkers synthesized diketopyrrolopyrrole-linked tetrabenzoporphyrin (DPP-BP) conjugates that have linear alkyl groups on the DPP moieties whose chain length is defined as n, namely, Cn-DPP-BP (n=4, 6, 8, or 10). For DPP-BP based solar cells, they demonstrated that alkyl chain length affects the power conversion efficiency. Therefore, it is very interesting to see how the local BHJ structures of DPP-BP based thin films affect the initial step of the charge carrier dynamics because such studies are difficult to perform for polymer-based systems. We can take advantage of small molecule-based systems to study the relationship between the local structure and the charge carrier dynamics. In this work, we used time-resolved terahertz (THz) spectroscopy to investigate the charge carrier dynamics of DPP-BP BHJ thin films blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). Time-resolved THz spectroscopy is a unique method to quantify charge carrier mobility with very fast time resolution (less than picosecond). This spectroscopy reflects the charge carrier dynamics in the local spatial region because of the high-frequency nature of the THz electric field. We chose C4-DPP-BP:PC61BM and C10-DPP-BP:PC61BM thin films for the THz measurements. In the previous study, it was found that C4-DPP-BP molecule prefers to take a face-on geometry on the substrate. A grain size of the aggregates was around 100 nm or smaller which were measured by atomic force microscopy. In such a structure, one can expect that charge transport takes place very efficiently to the electrode. Actually, power conversion efficiency is 5.2 % which is highest among a series of DPP-BP chromophores. On the other hand, C10-DPP-BP adopts an edge-on geometry on the substrate and forms micrometer-sized aggregates. In this structure, molecular stacking is oriented perpendicular to the electrode so that power conversion efficiency decreases to 0.19%. In contrast to the other measurements, the THz spectroscopy has sensitivity to in-plane motion of the charge carriers with respect to the substrate, we expect to observe higher in-plane mobility of the charge carriers in the C10-DPP-BP:PC61BM BHJ films compared to C4-DPP-BP based films. In contrast to our intuitive expectation, we found that the product of the carrier mobility and the yield of the photo-generated charge carriers is similar to each other. We consider that the similarity of the charge carrier dynamics results from the high-frequency nature of the local mobility of the polarons because most of the polarons are confined in less than a 10-nm length scale. Furthermore, the lowest limit of the carrier mobility obtained from our results is about 1.0 cm2V-1s-1 when the quantum yield of the charge carrier generation is assumed to be unity. This value is much higher than those obtained by space-charge-limited current method. We expect that charge separation occurs very efficiently when the local mobility of the charge carrier is high. In this contribution, we will present importance of the local mobility of the charge carriers and difference of charge transport between short and long length scales in DPP-BP based solar cells.
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Chamola, Paritosh, and Poornima Mittal. "Flexible organic solar cell to power modern cardiac pacemakers: Versatile for all age groups, skin types and genders." Physica Scripta, February 9, 2023. http://dx.doi.org/10.1088/1402-4896/acbac8.
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Abstract Bio-medical electronic components execute an vital part in medical services. Powering these devices is a task. Thus, the biomedical electronic devices which are able to self-harvest and store power are in huge demand. Present pacemakers are powered by batteries which have limited volume for energy packing and are compulsory to be changed. This needs a surgical intervention and is costly, with attachment of complications and risk. The objective of this paper is to validate if a subdermal PPV-PCBM [poly (2-methoxy-5-{3’,7’-dimethyloctyloxy}-p-phenylene vinylene) and {6,6}-phenyl C61 – butyric acid methyl ester] active layer bulk heterojunction (BHJ) organic photo-voltaic (OPV) device could power a cardiac pacemaker. Power yield of 0.05 milliWatts (mW), 0.45 milliWatts & 2.1 milliWatts for African, Asian & Caucasian skin tones are gained at 2-millimeter implementation depth, acceptable to operate cardiac pacemaker demanding approximate power of 10 microWatts. Additionally, results correspondingly display higher output power is generated if the skin is thinner and brighter.
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Mori, Shigehiko, Haruhi Oh-oka, Hideyuki Nakao, Takeshi Gotanda, Yoshihiko Nakano, Hyangmi Jung, Atsuko Iida, et al. "Organic photovoltaic module development with inverted device structure." MRS Proceedings 1737 (2015). http://dx.doi.org/10.1557/opl.2015.540.
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ABSTRACTThe power conversion efficiency (PCE) of organic photovoltaic (OPV) modules with 9.5% (25 cm2) and 8.7% (802 cm2) have been demonstrated. This PCE of the module exceeded our previous world records of 8.5% (25 cm2) and 6.8% (396 cm2) that were listed in the latest Solar Cell Efficiency Tables ver.43 [1]. Both module design and coating/patterning technique were consistently studied for module development. In order to achieve highly efficient modules, we increased the ratio of photo-active area to designated illumination area to 94% without any scribing process and placed insulating layers in order to decrease the leakage current. The meniscus coating method was used for the fabrication of both buffer and photoactive layers. This technique ensures the fabrication of uniform and nanometer order thickness layers with thickness variation less than 3%. Furthermore, the PCE of the OPV under indoor illumination was found to be higher than that of the conventional Si type solar cells. This indicates that OPVs are promising as electrical power supplies for indoor applications. Therefore, we have also developed several prototypes for electronics integrated photovoltaics (EIPV) such as electrical shelf labels and wireless sensors embedded with our OPV modules, which can be operated by indoor lights.
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Ohmori, Yutaka, Hirotake Kajii, Takayuki Taneda, and Masamitsu Kaneko. "Organic Light Emitting Diodes and Photo Detectors Fabricated on a Polymeric Substrate for Flexible Optical Integrated Devices." MRS Proceedings 769 (2003). http://dx.doi.org/10.1557/proc-769-h4.4.
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AbstractDirect fabrication of organic light emitting diodes (OLED) on a polymeric substrate, i.e., polymeric waveguide substrate to form a flexile optical integrated devices has been realized. The OELD was fabricated by organic molecular beam deposition (OMBD) technique on a polymeric substrate and a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signal of faster than 100 MHz has been created by applying pulsed voltage directly to the OLED with emissive layers utilizing rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives. Optical signal transmission with OLED fabricated on a polymeric waveguide with optical connectors has been successfully realized. Optical photo detectors (OPD) utilizing phthalocyanine derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with 5 MHz of cut-off frequency has been realized with superlattice structure under reverse bias voltage to the OPD.
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Ramirez, Ivan, Alberto Privitera, Safakath Karuthedath, Anna Jungbluth, Johannes Benduhn, Andreas Sperlich, Donato Spoltore, Koen Vandewal, Frédéric Laquai, and Moritz Riede. "The role of spin in the degradation of organic photovoltaics." Nature Communications 12, no. 1 (January 20, 2021). http://dx.doi.org/10.1038/s41467-020-20601-6.
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AbstractStability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet oxygen production or fullerene dimerization. The latter is thought to proceed from unquenched singlet excitons that have undergone intersystem crossing (ISC). Instead, we show that in bulk heterojunction (BHJ) solar cells the photo-degradation of C60 via photo-oligomerization occurs primarily via back-hole transfer (BHT) from a charge-transfer state to a C60 excited triplet state. We demonstrate this to be the principal pathway from a combination of steady-state optoelectronic measurements, time-resolved electron paramagnetic resonance, and temperature-dependent transient absorption spectroscopy on model systems. BHT is a much more serious concern than ISC because it cannot be mitigated by improved exciton quenching, obtained for example by a finer BHJ morphology. As BHT is not specific to fullerenes, our results suggest that the role of electron and hole back transfer in the degradation of BHJs should also be carefully considered when designing stable OPV devices.
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S M, Nitin Bala. "A Review on Current State, Recent Developments and Future Prospects of Dye Sensitized Solar Cells." International Journal of Research Publication and Reviews, October 22, 2022, 1629–36. http://dx.doi.org/10.55248/gengpi.2022.3.10.58.
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The sun is a primary abundant renewable source of energy for most of the life forms in our planet. By fully grasping the power of the sun, we can improve our way of life, reduce our dependence on fossil fuels or other types of energy sources and stimulate economy by bringing new jobs to all our planet industry. Among sustainable and renewable energy sources, solar cell, also known as photovoltaic cell, is one of the promising options of renewable energy and the most efficient. For the past several years, different photovoltaic devices like inorganic, organic and hybrid solar cells are invented for different application purposes. Regardless of its high conversion rate of silicon-based solar cells, the high module cost and complicated production process restricted their application. Research has been focused on alternative organic solar cells for their inherent low module cost and easy fabrication processes. Dye sensitized solar cell (DSSC) is considered to be one of the most promising, efficient, low-cost organic solar cells in recent years. DSSC, being transparent to some extent and comparatively cheaper than conventional solar photo-voltaic, can be a potential energy source for the future. This review paper focuses on the working of DSSC, its current state and recent developments in the various components of DSSC. The perspectives for the future development of the technology have also been discussed.
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Kabir, Shahriar, Yukiko Takayashiki, Jun-ichi Hanna, and Hiroaki IINO. "Solution processed near-infrared organic photodetector based on a liquid crystalline phthalocyanine derivative for vital signal monitoring." Japanese Journal of Applied Physics, December 9, 2022. http://dx.doi.org/10.35848/1347-4065/acaa42.
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Abstract In this study, near-infrared (NIR) organic photodetectors (OPDs) based on a liquid crystalline phthalocyanine derivative, octaoctyl-phthalocyanine (8H2Pc), and phenyl-C61-butyric-acid-methyl-ester (PC61BM) were realized. The champion device was found at the blend ratio of 1:1 by weight and exhibited responsivity of 0.2 A/W, external quantum efficiency of 29%, and shot-noise-limited specific detectivity of 1.3 × 1012 Jones at 740 nm with -1 V reverse bias. This notable performance was attributed to the uniformity and smooth surface morphology of the spin-coated active layer and the intermixed condition of the liquid crystalline 8H2Pc and PC61BM, resulting in smaller domain sizes and better separation of photo generated exciton pairs. Finally, the future prospect of the realized NIR OPD in practical applications was demonstrated by monitoring the vital signals of a human subject with a very simple experimental setup.