Effects of organic solvents for the phenyl-C61-butyric acid methyl ester layer on the performance of inverted perovskite solar cells

Abstract

We fabricated inverted perovskite solar cells (PSCs) using different organic solvents, including chloroform, chlorobenzene, and 1,2-dichlorobenzene, to prepare the phenyl-C61-butyric acid methyl ester (PCBM) layer. We found that using 1,2-dichlorobenzene resulted in smoother PCBM morphology compared to the chloroform-and chlorobenzene-based solvents; this would be beneficial for improving charge transport between the perovskite and cathode. In accordance with the morphologies, the average power conversion efficiency (PCE) of 1,2-dichlorobenzene-processed PSCs was 17.5%, which was higher than those of chlorobenzene-and chloroform-processed PSCs (16.7% and 11.0%, respectively) The best-performing cell was fabricated using 1,2-dichlorobenzene, showing PCEs of 17.9% and 18.2% in forward and reverse scans, respectively. We found that the conductivity and the PCBM surface roughness showed good linear dependence on the evaporation rate of the solvent, which could be an important factor for identifying new good organic solvents.