High Efficiency Perovskite Solar Cells by a Modified Low-Temperature Solution Process Inter-Diffusion Method

A modified inter-diffusion method to fabricate methylammoium lead iodide (MAPbI3) perovskite solar cell is proposed. A high quality perovskite active layer with thickness over 400 nm and grain sizes over 1 um was fabricated by the controlled solvent-assist annealing technique. (6,6)-Phenyl-C61-butyric acid methyl ester (PCBM) was used as the electron transport layer (ETL) to suppress the hysteresis. The performance dependence of solvent-assisted annealing and PCBM thickness was investigated. The highest power conversion efficiency (PCE) of 16.3% is obtained for a thick perovskite layer with reduced pin-holes and large grain sizes. A large external quantum efficiency (EQE) of 90% is obtained between 400-500 nm and it remains above 70% up to 700 nm.