Minimized defective trap sites in perovskite absorber films by coumarin dye for efficient and reliable perovskite solar cells

Abstract

This study presents a defect passivation approach using coumarin dye (7-diethylaminobenzopyran-2-one) as a multi-functional passivating agent of perovskite films to boost power conversion efficiency (PCE) and operating stability of PSCs. The coumarin dye could offer strong interaction with under-coordinated Pb2+ and vacant I− in [PbI6] octahedral frameworks due to multiple functional groups, which could serve as potential Lewis bases or hydrogen bonding sites, as well as highly conjugated aromaticity. The incorporation of coumarin dye contributes to improved film morphology of perovskite films, leading to compact and uniform grains without compromising crystallinity. Correspondingly, enhanced carrier extraction/transport and suppressed trap-assisted recombination are promoted in the perovskite films modified with coumarin dye. As a result, the coumarin dye incorporation improved the photovoltaic performance delivering a PCE of 20.85 % in planar p-i-n PSCs. The optimized device also recorded excellent indoor photovoltaic performance (PCE = 30.35 %) under dim-light condition. Furthermore, the devices passivated with coumarin dye also maintained >90 % of their initial PCEs after exposed under continuous indoor lighting irradiation (1000 lux) in ambient atmosphere for 2000 h, exhibiting impressive reliability and practical applicability.