Highly efficient inverted perovskite solar cells based on self-assembled graphene derivatives

The performance of inverted perovskite solar cells (PSCs) based on graphene oxide hole transporting materials is still unsatisfactory due to the high degree of surface oxygen contents and the insulating properties. In this study, thickness-controlled and full-coverage graphene oxide films prepared using a layer-by-layer self-assembly technique are first developed as hole transporting layers for PSCs. Meanwhile, conductivity-tunable reduced graphene oxide films are in situ prepared using an environment-friendly and efficient reductant system. A superior PCE of 16.28% based on the as-prepared rGO is obtained, resulting in an increment by approximately 33% compared with 12.26% of the device based on GO-1 as mentioned. At the same time, this work reveals an anomalous charge-extraction behavior of PSCs based on GO or rGO HTLs. The competitive effect of interfacial recombination, charge transportation and radiation recombination in this process is proposed to analyze the internal mechanisms. This work provides a facile and novel method to prepare GO or rGO films, which can be used as efficient charge-extraction layers and even as electrodes in inverted PSCs.