Institute for Physics and Astronomy, University of Potsdam , Karl-Liebknecht-Straße 24-25, Potsdam-Golm 14476, Germany.
Department of Chemistry and The Materials Research Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
ACS Appl Mater Interfaces. 2017 Dec 6;9(48):42011-42019. doi: 10.1021/acsami.7b10361. Epub 2017 Nov 17.
Hybrid lead halide perovskites are introduced as charge generation layers (CGLs) for the accurate determination of electron mobilities in thin organic semiconductors. Such hybrid perovskites have become a widely studied photovoltaic material in their own right, for their high efficiencies, ease of processing from solution, strong absorption, and efficient photogeneration of charge. Time-of-flight (ToF) measurements on bilayer samples consisting of the perovskite CGL and an organic semiconductor layer of different thickness are shown to be determined by the carrier motion through the organic material, consistent with the much higher charge carrier mobility in the perovskite. Together with the efficient photon-to-electron conversion in the perovskite, this high mobility imbalance enables electron-only mobility measurement on relatively thin application-relevant organic films, which would not be possible with traditional ToF measurements. This architecture enables electron-selective mobility measurements in single components as well as bulk-heterojunction films as demonstrated in the prototypical polymer/fullerene blends. To further demonstrate the potential of this approach, electron mobilities were measured as a function of electric field and temperature in an only 127 nm thick layer of a prototypical electron-transporting perylene diimide-based polymer, and found to be consistent with an exponential trap distribution of ca. 60 meV. Our study furthermore highlights the importance of high mobility charge transporting layers when designing perovskite solar cells.
混合卤化铅钙钛矿被引入作为电荷产生层 (CGL)，以准确确定薄有机半导体中的电子迁移率。由于其高效率、易于溶液处理、强吸收和高效光生电荷，此类混合钙钛矿已成为一种广泛研究的光伏材料。实验结果表明，由钙钛矿 CGL 和不同厚度的有机半导体层组成的双层样品的飞行时间 (ToF) 测量结果由载流子在有机材料中的运动决定，这与钙钛矿中更高的电荷载流子迁移率一致。结合钙钛矿中高效的光子到电子的转换，这种高迁移率不平衡使得在相对较薄的与应用相关的有机薄膜上进行电子迁移率的测量成为可能，而传统的 ToF 测量则无法实现。这种结构使得电子选择性的迁移率测量可以在单个组件以及体异质结薄膜中进行，正如在典型的聚合物/富勒烯混合物中所证明的那样。为了进一步展示这种方法的潜力，在只有 127nm 厚的典型电子传输苝二酰亚胺基聚合物层中，测量了电子迁移率作为电场和温度的函数，发现其与约 60meV 的指数陷阱分布一致。我们的研究进一步强调了在设计钙钛矿太阳能电池时，高迁移率电荷传输层的重要性。
