As perovskite solar cells (PSCs) are composed of multilayer structures, the formation of an appropriate interface between the perovskite lightabsorbing layer and charge transport layer is necessary to achieve a high power conversion efficiency (PCE). [6,6]-phenyl C61 butyric acid methyl ester (PCBM) is a popular organic material for the electron transport layer (ETL) in PSCs owing to its solution processability and excellent n-type properties. However, the annealing effects of the PCBM ETL on PSC performance are not adequately understood. Therefore, we fabricated p-i-n structured PSCs with annealed and unannealed PCBM ETL, and their device performances were compared. The PCE of the PSCs was markedly increased by annealing of the PCBM. The improved device performance resulted from the (1) enhanced electron transport ability of PCBM and (2) reduced non-radiative recombination at the interface between the perovskite and PCBM. These results show that annealing of PCBM is an efficient method to attain a high PCE of PSCs.

Keywords: Perovskite solar cell, PCBM, Electron transport layer, Annealing process