Surface p-Type Self-Doping Facilitating the Enhanced Performance of Air-Processed Carbon-Based Perovskite Solar Cells

Abstract

The fabrication of perovskite solar cells (PSCs) in the ambient environment offers considerable promise for practical applications, yet it also poses considerable challenges. Water is known to cause structural deterioration, which has a negative effect on the stability and efficiency of perovskite-based devices. The presence of defects is believed to provide pathways for water infiltration into the perovskite. Therefore, one important strategy for avoiding perovskite hydration is the passivation of perovskite defects. Herein, a simple antisolvent additive engineering approach is employed. By adding the additive with functional groups of CO, NH₂, and CF₃ to the antisolvent ethyl acetate, the defects in the perovskite thin film are successfully reduced and significantly mitigated the possibility of H₂O infiltrating the perovskite lattice through the defects. Additionally, the addition of methyl 2-amino-4-(trifluoromethyl)benzoate results in a p-type self-doping effect at the interface of the perovskite film, thereby improving hole extraction and transport. The power conversion efficiency of hole-transport layer-free carbon-based PSCs fabricated in ambient air conditions is 19.17% (0.04 cm²) and 17.78% (1 cm²), respectively. Moreover, the optimized unencapsulated devices retain 90.6% of their original efficiency after being kept for 1200 h in conditions of 70% relative humidity.