Asymmetric perinone-based electron-collecting monolayer materials for n–i–p perovskite solar cells†

A series of asymmetric perinone derivatives (PERNI) bearing different substituents (methyl, fluoro, chloro, bromo, and cyano) on the benzimidazole moiety were synthesized and investigated for possible application as electron-collecting monolayer materials in negative–intrinsic–positive perovskite solar cells. These compounds exhibit good thermal stability and suitable frontier molecular orbital energy levels for electron extraction and hole blocking. The perinone-based devices were found to demonstrate comparable power conversion efficiencies and higher operational stability than reference devices using the representative naphthalene diimide-based monolayer material under the same fabrication conditions. Within the PERNI series, devices fabricated with the chloro-substituted PERNI-Cl were found to tend to exhibit the highest open-circuit voltage and fill factor owing to the smallest energy offset between the lowest unoccupied molecular orbital and the conduction band of the perovskite.