Efficiency enhancement of perovskite solar cells by forming a tighter interface contact of C/CH3NH3PbI3

Carbon materials have been gradually applied to perovskite solar cells as counter electrode. However, there always exists a poor interface contact between carbon and perovskite layer (C/CH3NH3PbI3), resulting in inferior performances. Herein, we introduce an additive of acetonitrile (ACN) into carbon slurry, which effectively improves the interface contact of C/CH3NH3PbI3. Because of a medium solubility for perovskite, ACN will dissolve the surface crystal of perovskite layer when the carbon slurry is doctor-bladed on the top of CH3NH3PbI3 film, which will form a liquid/liquid interface between C/CH3NH3PbI3, leading to a tighter contact. In addition, many surface grains of perovskite layer will get smaller after treated with ACN, which will enhance the light scattering performance of perovskite layer. By optimization toward the content of ACN in carbon slurry, the interface contact of C/CH3NH3PbI3 and the photovoltaic performance have been significantly improved. Compared to 7.45% of the control device, an optimal power conversion efficiency of 8.32% has been achieved for low-temperature carbon based perovskite solar cells, which shows great potential in future application.