Interface Regulation via an Organometallic Ferrocene-Based Molecule toward Inverted Perovskite Solar Cells

There is a significant challenge of charge recombination at the perovskite/electron transport layer (ETL), coupled with the need of optimized interface charge transfer in inverted perovskite solar cells (PSCs). In this work, an organometallic ferrocene-based molecule, ferrocenyl-bis-thieno[3,2-b]thiophene-2-carboxylate (FcTTPc), with inherent carboxylate and thiophene functionalities surrounding the central ferrocene motif, is meticulously designed and synthesized for the modification of the perovskite/ETL interface. The carboxylate and thiophene groups in the FcTTPc molecule interact strongly with perovskite components, effectively passivating interface defects. Furthermore, the thiophene group of FcTTPc can engage in robust pi-pi interactions with the ETL, thereby enhancing interface charge transport. Following the interface modification with FcTTPc, an improved alignment of energy levels is achieved, significantly optimizing carrier transport. Due to the interface modification via the FcTTPc molecule, the champion PSC achieves a PCE of 25.39%. The FcTTPc-modified devices maintained over 96% of their initial efficiency under 40% relative humidity conditions for 1500 h.