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Solar Cells: Electrical Performance of Organic Solar Cells with Additive‐Assisted Vertical Phase Separation in the Photoactive Layer (Adv. Energy Mater. 2/2014) 
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下载免费PDF全文 Min Kim Joo‐Hyun Kim Hyun Ho Choi Jong Hwan Park Sae Byeok Jo Myungsun Sim Jong Soo Kim Hiroshi Jinnai Yeong Don Park Kilwon Cho 《Liver Transplantation》2014,4(2)
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Ardalan Armin Gytis Juska Mujeeb Ullah Marappan Velusamy Paul L. Burn Paul Meredith Almantas Pivrikas 《Liver Transplantation》2014,4(4)
A novel technique based upon injection‐charge extraction by linearly increasing voltage (i‐CELIV) in a metal‐insulator‐semiconductor (MIS) diode structure is described for studying charge transport in organic semiconductors. The technique (MIS‐CELIV) allows selective measurement of both electron and hole mobilities of organic solar cells with active layers thicknesses representative of operational devices. The method is used to study the model high efficiency bulk heterojunction combination poly[N‐9′′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT) and [6,6]‐phenyl C70‐butyric acid methyl ester (PC70BM) at various blend ratios. The absence of bipolar transport in PCDTBT‐and‐PC70BM‐only diodes is shown and strongly imbalanced carrier mobility is found in the most efficient “optimized” blend ratios. The mobility measurements are correlated with overall device performance and it is found that balanced and high charge carrier mobility are not necessarily required for high efficiencies in thin film organic solar cells. 相似文献
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Aung Ko Ko Kyaw Dong Hwan Wang Chan Luo Yong Cao Thuc‐Quyen Nguyen Guillermo C. Bazan Alan J. Heeger 《Liver Transplantation》2014,4(7)
The effects of solvent additive (1,8‐diiodooctane (DIO)) on the morphology, charge generation, transport, and recombination in solution‐processed small‐molecule solar cells are studied and these parameters are correlated with device performance. In the optimum nanoscale morphology, which is processed with 0.4% DIO, the phase separation is large enough to create a percolating pathway for carrier transport, yet still small enough to form large interfacial area for efficient charge separation. Complete phase separation in this film reduces the interfacial defects, which occurs without DIO, and hence suppresses the monomolecular recombination. Moreover, balanced charge transport and weak bimolecular recombination lead to a high fill factor (72%). On the other hand, an excess amount of DIO (0.8%) in the solvent results in the over‐aggregation of the donor phase, which disturbs the percolating pathway of the acceptor phase and reduces the electron mobility. The over‐aggregation of the donor phase also shrinks the interfacial area for charge separation and consequently reduces the photocurrent generation. 相似文献
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Yiwen Wang Weixia Lan Ning Li Zhaojue Lan Zhen Li Jingnan Jia Furong Zhu 《Liver Transplantation》2019,9(19)
Remarkable progress has been made in the development of high‐efficiency solution‐processable nonfullerene organic solar cells (OSCs). However, the effect of the vertical stratification of bulk heterojunction (BHJ) on the efficiency and stability of nonfullerene OSCs is not fully understood yet. In this work, we report our effort to understand the stability of nonfullerene OSCs, made with the binary blend poly[(2,6‐(4, 8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′] dithiophene‐4,8‐dione)] (PBDB‐T):3,9‐ bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐ dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC) system. It shows that a continuous vertical phase separation process occurs, forming a PBDB‐T‐rich top surface and an ITIC‐rich bottom surface in PBDB‐T:ITIC BHJ during the aging period. A gradual decrease in the built‐in potential (V0) in the regular configuration PBDB‐T:ITIC OSCs, due to the interfacial reaction between the poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer and ITIC acceptor, is one of the reasons responsible for the performance deterioration. The reduction in V0, caused by an inevitable reaction at the ITIC/PEDOT:PSS interface in the OSCs, can be suppressed by introducing a MoO3 interfacial passivation layer. Retaining a stable and high V0 across the BHJ through interfacial modification and device engineering, e.g., as seen in the inverted PBDB‐T:ITIC OSCs, is a prerequisite for efficient and stable operation of nonfullerene OSCs. 相似文献
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Jhong‐Sian Wu Yu‐Ying Lai Yen‐Ju Cheng Chih‐Yu Chang Chien‐Lung Wang Chain‐Shu Hsu 《Liver Transplantation》2013,3(4):457-465
A new dithienobenzo‐carbazole (DTBC) heptacyclic arene using sp2‐sp2 dialkylethylene moiety as the bridge was successfully synthesized by Suzuki‐Miyaura cross‐coupling reaction. This facile benzoannulation planarizes the conjugated framework with the concomitant introduction of four octyl substituents, making the newly designed copolymer PDTBCDTBT exhibit solution processability, superior absorption ability, lower‐lying HOMO energy level, and crystalline nature. The solar cell using PDTBCDTBT has produced a high efficiency of 6.2%, which outperforms the corresponding sp3‐hybridized C‐bridged, Si‐bridged and N‐bridged analogous polymers. 相似文献
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Hamed Azimi Alessia Senes Markus C. Scharber Kurt Hingerl Christoph J. Brabec 《Liver Transplantation》2011,1(6):1162-1168
Charge transport and recombination are studied for organic solar cells fabricated using blends of polymer poly[(4,4′‐bis(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐(4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole)‐5,5′‐diyl] (Si‐PCPDTBT) with [6,6]‐phenyl‐C61‐butyric acid methyl ester (mono‐PCBM) and the bis‐adduct analogue of mono‐PCBM (bis‐PCBM). The photocurrent of Si‐PCPDTBT:bis‐PCBM devices shows a strong square root dependence on the effective applied voltage. From the relationship between the photocurrent and the light intensity, we found that the square‐root dependence of the photocurrent is governed by the mobility‐lifetime (μτ) product of charge carriers while space‐charge field effects are insignificant. The fill factor (FF) and short circuit current density (Jsc) of bis‐PCBM solar cells show a considerable increase with temperature as compared to mono‐PCBM solar cells. SCLC analysis of single carrier devices proofs that the mobility of both electrons and holes is significantly lowered when replacing mono‐PCBM with bis‐PCBM. The increased recombination in Si‐PCPDTBT:bis‐PCBM solar cells is therefore attributed to the low carrier mobilities, as the transient photovoltage measurements show that the carrier lifetime of devices are not significantly altered by using bis‐PCBM instead of mono‐PCBM. 相似文献
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Ardalan Armin Zhiming Chen Yaocheng Jin Kai Zhang Fei Huang Safa Shoaee 《Liver Transplantation》2018,8(7)
Charge extraction rate in solar cells made of blends of electron donating/accepting organic semiconductors is typically slow due to their low charge carrier mobility. This sets a limit on the active layer thickness and has hindered the industrialization of organic solar cells (OSCs). Herein, charge transport and recombination properties of an efficient polymer (NT812):fullerene blend are investigated. This system delivers power conversion efficiency of >9% even when the junction thickness is as large as 800 nm. Experimental results indicate that this material system exhibits exceptionally low bimolecular recombination constant, 800 times smaller than the diffusion‐controlled electron and hole encounter rate. Comparing theoretical results based on a recently introduced modified Shockley model for fill factor, and experiments, clarifies that charge collection is nearly ideal in these solar cells even when the thickness is several hundreds of nanometer. This is the first realization of high‐efficiency Shockley‐type organic solar cells with junction thicknesses suitable for scaling up. 相似文献
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Yilin Wang Xiaohui Wang Baojun Lin Zhaozhao Bi Xiaobo Zhou Hafiz Bilal Naveed Ke Zhou Hongping Yan Zheng Tang Wei Ma 《Liver Transplantation》2020,10(28)
Sequential deposition has great potential to achieve high performance in organic solar cells due to the resulting well‐controlled vertical phase separation. In this work, double bulk heterojunction organic solar cells are fabricated by sequential‐blade cast in ambient conditions. Probed by the in situ grazing incidence X‐ray diffraction and in situ UV–vis absorption measurements, the seq‐blade system exhibits a different tendency from each of the binary films during the film formation process. Due to the extensive aggregation of FOIC, the binary PBDB‐T:FOIC film displays a strong and large phase separation, resulting in low current density (Jsc) and unsatisfactory power conversion efficiency. In the seq‐blade cast system, the bottom layer PBDB‐T:IT‐M produces many crystal nuclei for the top layer PBDB‐T:FOIC, so the PBDB‐T molecules are able to crystallize easily and quickly. Balanced crystallization kinetics between polymer and small molecule and an ideal percolation network in the film are observed. In addition, the balanced crystallization kinetics are favorable toward realizing lower recombination loss through charge transport processes. 相似文献
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Jonathan A. Bartelt Jessica D. Douglas William R. Mateker Abdulrahman El Labban Christopher J. Tassone Michael F. Toney Jean M. J. Fréchet Pierre M. Beaujuge Michael D. McGehee 《Liver Transplantation》2014,4(9)
The bulk heterojunction (BHJ) solar cell performance of many polymers depends on the polymer molecular weight (M n) and the solvent additive(s) used for solution processing. However, the mechanism that causes these dependencies is not well understood. This work determines how M n and solvent additives affect the performance of BHJ solar cells made with the polymer poly(di(2‐ethylhexyloxy)benzo[1,2‐b:4,5‐b′]dithiophene‐co‐octylthieno[3,4‐c]pyrrole‐4,6‐dione) (PBDTTPD). Low M n PBDTTPD devices have exceedingly large fullerene‐rich domains, which cause extensive charge‐carrier recombination. Increasing the M n of PBDTTPD decreases the size of these domains and significantly improves device performance. PBDTTPD aggregation in solution affects the size of the fullerene‐rich domains and this effect is linked to the dependency of PBDTTPD solubility on M n. Due to its poor solubility high M n PBDTTPD quickly forms a fibrillar polymer network during spin‐casting and this network acts as a template that prevents large‐scale phase separation. Furthermore, processing low M n PBDTTPD devices with a solvent additive improves device performance by inducing polymer aggregation in solution and preventing large fullerene‐rich domains from forming. These findings highlight that polymer aggregation in solution plays a significant role in determining the morphology and performance of BHJ solar cells. 相似文献
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Jian Qing Xiao‐Ke Liu Mingjie Li Feng Liu Zhongcheng Yuan Elizaveta Tiukalova Zhibo Yan Martial Duchamp Shi Chen Yuming Wang Sai Bai Jun‐Ming Liu Henry J. Snaith Chun‐Sing Lee Tze Chien Sum Feng Gao 《Liver Transplantation》2018,8(21)
Recently, Ruddlesden–Popper perovskites (RPPs) have attracted increasing interests due to their promising stability. However, the efficiency of solar cells based on RPPs is much lower than that based on 3D perovskites, mainly attributed to their poor charge transport. Herein, a simple yet universal method for controlling the quality of RPP films by a synergistic effect of two additives in the precursor solution is presented. RPP films achieved by this method show (a) high quality with uniform morphology, enhanced crystallinity, and reduced density of sub‐bandgap states, (b) vertically oriented perovskite frameworks that facilitate efficient charge transport, and (c) type‐II band alignment that favors self‐driven charge separation. Consequently, a hysteresis‐free RPP solar cell with a power conversion efficiency exceeding 12%, which is much higher than that of the control device (1.5%), is achieved. The findings will spur new developments in the fabrication of high‐quality, aligned, and graded RPP films essential for realizing efficient and stable perovskite solar cells. 相似文献
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Charge‐transfer (CT) state electroluminescence is investigated in several polymer:fullerene bulk heterojunction solar cells. The ideality factor of the electroluminescence reveals that the CT emission in polymer:fullerene solar cells originates from free‐carrier bimolecular recombination at the donor‐acceptor interface, rather than a charge‐trap‐mediated process. The fingerprint of the presence of nonradiative trap‐assisted recombination, a voltage‐dependent CT electroluminescence quantum efficiency, is only observed for the P3HT:PCBM system, which is explained by a reduction of the competing bimolecular recombination rate. These results are in agreement with measurements of the illumination‐intensity dependence of the open‐circuit voltage. 相似文献
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John R. Tumbleston Yingchi Liu Edward T. Samulski Rene Lopez 《Liver Transplantation》2012,2(4):477-486
In this work, it is demonstrated that bimolecular recombination depends on the distance that free carriers are required to travel in transit to the electrodes in bulk heterojunction organic solar cells. By employing semi‐transparent devices, the carrier transport distance can be controlled via the local light absorption profile with an appropriate choice of the illumination side and incident wavelength. Using a series of light intensity‐dependent measurements, bimolecular recombination is shown to depend on the distance electrons or holes are required to transit the active layer. This effect is demonstrated for three different bulk heterojunction blends, where the restrictive carrier that causes the onset of recombination is identified. The mobility‐lifetime products of the limiting carriers are also estimated using a simple model for carrier extraction, where similar values are obtained regardless of the absorption profile. Implications for 1‐sun performance are also discussed, which provide guidelines for fabricating devices with thicker active layers capable of maximizing light absorption without succumbing to recombination losses. 相似文献
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Yilin Wang Qinglian Zhu Hafiz Bilal Naveed Heng Zhao Ke Zhou Wei Ma 《Liver Transplantation》2020,10(7)
As a predominant fabrication method of organic solar cells (OSCs), casting of a bulk heterojunction (BHJ) structure presents overwhelming advantages for achieving higher power conversion efficiency (PCE). However, long‐term stability and mechanical strength are significantly crucial to realize large‐area and flexible devices. Here, controlling blend film morphology is considered as an effective way toward co‐optimizing device performance, stability, and mechanical properties. A PCE of 12.27% for a P‐i‐N‐structured OSC processed by sequential blade casting (SBC) is reported. The device not only outperforms the as‐cast BHJ devices (11.01%), but also shows impressive stability and mechanical properties. The authors corroborate such enhancements with improved vertical phase separation and purer phases toward more efficient transport and collection of charges. Moreover, adaptation of SBC strategy here will result in thermodynamically favorable nanostructures toward more stable film morphology, and thus improving the stability and mechanical properties of the devices. Such co‐optimization of OSCs will pave ways toward realizing the highly efficient, large‐area, flexible devices for future endeavors. 相似文献