Charge carrier mobility of the organic photovoltaic materials PTB7 and PC71BM and its influence on device performance
Charge carrier mobility of the organic photovoltaic materials PTB7 and PC71BM and its influence on device performance
复制标题
DOI：
10.1016/j.orgel.2015.03.013
复制
发表时间：
2015-07-01
影响因子：
3.2
通讯作者：
Samuel, Ifor D. W.
中科院分区：
文献类型：
--
作者：
Ebenhoch, Bernd;Thomson, Stuart A. J.;Samuel, Ifor D. W.
迁移率是有机太阳能电池材料的重要参数，因为它影响电荷提取和复合动力学。在本研究中，利用飞行时间技术研究重要有机光伏材料PC71BM、PTB7及其混合物的电荷迁移率。对于纯富勒烯薄膜，PC71BM的电子迁移率在1 x 10(-3) cm(2)/Vs范围内，并且具有正电场依赖性。在室温下，纯薄膜的PTB7 空穴迁移率为1 x 10(-3) cm(2)/Vs，其混合物的空穴迁移率为2 x 10(-4) cm(2)/Vs。当样品从室温冷却到 77 K 时，混合物的空穴迁移率降低了千分之一。这一发现与高效 PTB7:PC71BM 太阳能电池在不同温度下的器件性能进行了比较。在 77 K 时，由于填充因子和短路电流的损失，太阳能电池的效率减半。双分子和陷阱辅助复合在低迁移率（低温）条件下增加，而在高迁移率条件下开路电压降低。作为温度函数的功率转换效率在 260 K 至 295 K 之间具有最大值，显示出室温下的优化迁移率。 (C) 2015 年作者。由 Elsevier B.V. 出版
The mobility is an important parameter for organic solar cell materials as it influences the charge extraction and recombination dynamics. In this study, the time of flight technique is used to investigate the charge mobility of the important organic photovoltaic materials PC71BM, PTB7 and their blend. The electron mobility of PC71BM is in the region of 1 x 10(-3) cm(2)/Vs for the neat fullerene film, and has a positive electric field dependence. At room temperature the hole mobility of PTB7 is 1 x 10(-3) cm(2)/Vs for the neat film and 2 x 10(-4) cm(2)/Vs for their blend. The hole mobility of the blend reduces by a factor of a thousand when the sample is cooled from room temperature to 77 K. This finding is compared with the device performance of efficient PTB7:PC71BM solar cells for varying temperature. At 77 K the solar cell efficiency halved, due to losses in fill factor and short circuit current. Bimolecular and trap-assisted recombination increase at low mobility (low temperature) conditions, whereas at high mobility conditions the open circuit voltage reduces. The power conversion efficiency as a function of temperature has a maximum between 260 K and 295 K, revealing an optimized mobility at room temperature. (C) 2015 The Authors. Published by Elsevier B.V.