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⁺ defects. The PSCs treated with DOPA 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.