Inverted Perovskite Solar Cells with Efficient Mixed‐Fullerene Derivative Charge Extraction Layers

Abstract

AbstractThe short‐circuit current density of inverted perovskite solar cells is unsatisfactory due to the intrinsic relatively low electron mobility and electrical conductivity of PC61BM. To solve this problem, a solution‐processed mixed‐fullerene derivative electron transporting material by mixing PC61BM with C60 was developed to improve charge extraction capacity in fully low temperature processed devices. Incorporation of C60 into the PC61BM layer improves the mobility from 2.15×10−3 to 4.71×10−3 cm2⋅V−1⋅s−1 and the conductivity of electron transporting layers, thus enhancing the interfacial electron extraction capacity and reducing the electron transfer resistance. As a result, the average power conversion efficiency increases from 12.80% to 15.47% by 21% due to the significant increases in the average short‐circuit current density from 19.26 to 22.08 mA⋅cm−2 by 15%. Meanwhile, the optimal efficiency of 16.44% with rigid substrates and 12.93% with flexible substrates are obtained with almost no hysteresis. This work provides a novel and simple method to greatly improve the short‐circuit current density and hence the photovoltaic performance of inverted perovskite solar cells.