The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yoshiaki Nakano - One of the best experts on this subject based on the ideXlab platform.
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a superlattice solar cell with enhanced Short Circuit Current and minimized drop in open Circuit voltage
IEEE Journal of Photovoltaics, 2012Co-Authors: Yunpeng Wang, Yu Wen, Hassanet Sodabanlu, Kentaroh Watanabe, Masakazu Sugiyama, Yoshiaki NakanoAbstract:A quantum-well (QW) solar cell including InGaAs wells is a promising candidate for the purpose of Current matching in InGaP/GaAs/Ge tandem solar cells by extending the edge of quantum efficiency to longer wavelengths. Even though QWs increase Short-Circuit Current by the extended effective band edge, they tend to obstruct carrier transport and degrade the efficiency of a cell. Therefore, a superlattice (SL) structure has been proposed to prevent the recombination of carriers inside of the wells and, more importantly, to enable carriers to tunnel to a neighboring well, leading to an efficient carrier transportation in such a photovoltaic device. In this paper, a SL solar cell was implemented with a strain-balancing technique. It exhibited excellent performance: Enhanced photoCurrent (3.0 mA/cm $^2$ ) with minimized drop (0.03 V) in open-Circuit voltage. Behind these achievements, substantial contribution of tunneling transport has been confirmed for the SL cell by external quantum efficiency measurement at 77 K.
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a superlattice solar cell with enhanced Short Circuit Current and minimized drop in open Circuit voltage
Photovoltaic Specialists Conference, 2011Co-Authors: Yunpeng Wang, Hassanet Sodabanlu, Kentaroh Watanabe, Masakazu Sugiyama, Yoshiaki NakanoAbstract:Multiple quantum wells (MQWs) solar cell can increase the quantum efficiency of solar cell devices. Extra adsorption from quantum wells at longer wavelengths leads to a photovoltaic device with a high-density Current output, which can solve the issue of Current matching in tandem solar cells. However, enhancement in Current density of a cell usually necessitates deeper wells in MQWs. As a result, open-Circuit voltage would suffer from serious degradation due to a reduced quasi-Fermi-level splitting. Therefore, an optimization of a MQWs solar cell presents a trade-off between open-Circuit voltage and Short-Circuit Current. Our strategy is to avoid narrowing of the bandgap for the well material while maximizing the quantum efficiency in the sub-bandgap wavelength of the host material. This necessitates enhancement in carrier escape, which in turn requires thin enough barriers to allow tunneling of electrons and holes over an entire set of superlattice (SL). In this study, by the use of interface management technique for the crystal growth of MQWs, we have successfully implemented an ultra high efficiency SL solar cell by reducing the barrier thickness to 3.1 nm. For this cell, an increment of I sc as large as 3.0 mA/cm2 was obtained as compared to a control GaAs p-i-n cell. A remarkable achievement was quite a small degradation in V oc , 0.02V, in spite of substantial increment in I sc . An overall efficiency was 18%, which was a bit larger than that of the GaAs p-i-n control cell. Behind that remarkable achievement of almost no degradation in total conversion efficiency associated with the inclusion of quantum wells and enhanced output Current, substantial contribution of tunneling transport has been confirmed for the SL cell by external quantum efficiency measurement at 77K.
Shijian Su - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous enhancement of open-Circuit voltage, Short-Circuit Current density, and fill factor in polymer solar cells
Advanced Materials, 2011Co-Authors: Zhicai He, Chengmei Zhong, Hongbin Wu, Wai-yeung Wong, Liwei Chen, Xun Huang, Shijian SuAbstract:Simultaneous enhancement of open-Circuit voltage, Short-Circuit Current density, and fill factor in highly efficient polymer solar cells by incorporating an alcohol/water-soluble conjugated polymer as cathode interlayer is domonstrated. When combined with a low-bandgap polymer PTB7 as the electron donor material, the power efficiency of the devices is improved to a certified 8.370%. Due to the drastic improvement in efficiency and easy utilization, this method opens new opportunities for PSCs from various material systems to improve towards 10% efficiency.
Thomas P Russell - One of the best experts on this subject based on the ideXlab platform.
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small molecule solar cells with simultaneously enhanced Short Circuit Current and fill factor to achieve 11 efficiency
Advanced Materials, 2017Co-Authors: Li Nian, Ke Gao, Yufeng Jiang, Qikun Rong, Dong Yuan, Feng Liu, Xiaobin Peng, Thomas P RussellAbstract:High-efficiency small-molecule-based organic photovoltaics (SM-OPVs) using two electron donors (p-DTS(FBTTh2)2 and ZnP) with distinctively different absorption and structural features are reported. Such a combination works well and synergically improves device Short-Circuit Current density (Jsc) to 17.99 mA cm−2 and fill factor (FF) to 77.19%, yielding a milestone efficiency of 11%. To the best of our knowledge, this is the highest power conversion efficiency reported for SM-OPVs to date and the first time to combine high Jsc over 17 mA cm−2 and high FF over 77% into one SM-OPV. The strategy of using multicomponent materials, with a selecting role of balancing varied electronic and structural necessities can be an important route to further developing higher performance devices. This development is important, which broadens the dimension and versatility of existing materials without much chemistry input.
Zhenan Bao - One of the best experts on this subject based on the ideXlab platform.
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controlled conjugated backbone twisting for an increased open Circuit voltage while having a high Short Circuit Current in poly hexylthiophene derivatives
Journal of the American Chemical Society, 2012Co-Authors: Eric T Hoke, Laxman Pandey, Sanghyun Hong, Rajib Mondal, Chad Risko, Rodrigo Noriega, Michael D Mcgehee, Jeanluc Bredas, Alberto Salleo, Zhenan BaoAbstract:Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-Circuit voltages in solar cells, though with decreased Short-Circuit Current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-Circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone--due to an increase in the polymer ionization potential--while the Short-Circuit Current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2':5',2''-terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-Circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar Short-Circuit Current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-Circuit voltage while retaining the Short-Circuit Current.
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controlled conjugated backbone twisting for an increased open Circuit voltage while having a high Short Circuit Current in poly hexylthiophene derivatives
Journal of the American Chemical Society, 2012Co-Authors: Eric T Hoke, Laxman Pandey, Sanghyun Hong, Rajib Mondal, Chad Risko, Rodrigo Noriega, Michael D Mcgehee, Jeanluc Bredas, Alberto Salleo, Zhenan BaoAbstract:Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-Circuit voltages in solar cells, though with decreased Short-Circuit Current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-Circuit voltage and...
Shaopeng Yang - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous enhancement of Short-Circuit Current density, open Circuit voltage and fill factor in ternary organic solar cells based on PTB7-Th:IT-M:PC71BM
Solar Energy Materials and Solar Cells, 2018Co-Authors: Guang Li, Zhaoxiang Huai, Shahua Huang, Lixin Wang, Guangsheng Fu, Shaopeng YangAbstract:Abstract Recently, studies on ternary organic solar cells (OSCs) have revealed their potentials for achieving the improved device performances. However, owing to the trade-off between the Short-Circuit Current density J SC ) and open Circuit voltage ( V OC ), the mismatch of the energy levels between donors and acceptors leads to a large energy loss and then leads to a lower V OC in most ternary systems. In this study, we incorporated 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)− 5-methylindanone)− 5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b’]-dithiophene (IT-M) into a PTB7-Th:PC 71 BM host system as the third component, which has a higher energy level of the lowest unoccupied molecular orbital (LUMO) than that of PC 71 BM. The introduction of IT-M adjusts the energy-level cascade, enhances the absorption intensity and modulates the film morphology, which facilitate the charge generation, enhance the charge transport, and suppress the charge recombination, as manifested by the significantly enhanced V OC , J SC , and fill factor (FF). Therefore, the results indicate that a simultaneous enhancement of V OC , J SC , and FF can be achieved by incorporation of IT-M in ternary OSCs, providing a higher efficiency.