Bioinspired molecules design for bilateral synergistic passivation in buried interfaces of planar perovskite solar cells

Trap-mediated energy loss in the buried interface with non-exposed feature constitutes one of the serious challenges for achieving high-performance perovskite solar cells (PSCs). Inspired by the adhesion mechanism of mussels, herein, three catechol derivatives with functional Lewis base groups, namely 3,4-Dihydroxyphenylalanine (DOPA), 3,4-Dihydroxyphenethylamine (DA) and 3-(3,4-Dihydroxyphenyl) propionic acid (DPPA), were strategically designed. These molecules as interfacial linkers are incorporated into the buried interface between perovskite and SnO2 surface, achieving bilateral synergetic passivation effect. The crosslinking can produce secondary bonding with the undercoordinated Pb2+ and Sn4+ exhibited the best performance and operational stability. Upon the DOPA passivation, a stabilized power conversion efficiency (PCE) of 21.5% was demonstrated for the planar PSCs. After 55 days of room-temperature storage, the unencapsulated devices with the DOPA crosslinker could still maintain 85% of their initial performance in air under relative humidity of ≈15%. This work opens up a new strategy for passivating the buried interfaces of perovskite photovoltaics and also provides important insights into designing defect passivation agents for other perovskite optoelectronic devices, such as light-emitting diodes, photodetectors, and lasers.