The synergistic passivation effect of functionally doped povidone-iodine on quasi-2D perovskite solar cells

Two-dimensional metallic halide perovskites with interlayer alternating cations (ACI) have shown great potential in photovoltaics. Compared to their Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) counterparts, ACI perovskites have a narrower band gap (E_g) and enhanced optical absorption. However, the relatively low power conversion efficiency (PCE) hampers the development of ACI-based devices due to their crystal orientation and quality. In this paper, a method of passivation of hybrid GAMA_nPb_nI_3n+1 (n = 5) perovskites by additive engineering was reported. Inverted perovskite solar cells (PSCs) were prepared by adding polyvinylpyrrolidone (PVP) and povidone-iodine (PVP-I), and the synergistic passivation effect of PVP and I was investigated. The optimal PVP-I concentration reduces the trap density, and enhances the charge mobility and transport because of the improved crystallinity and energy cascade, which eventually generates a PCE of 15.73%. Additionally, the optimized devices without encapsulation retain 80% of their initial efficiency for more than 700 h after storage under ambient conditions.