Amino acid salt induced PbI2 crystal orientation optimization for high-efficiency perovskite solar cells with long-term stability

Abstract

The two-step method presents an efficient means to streamline the fabrication process of high-quality and reproducible perovskite films, making it a more suitable option for the fabrication of large-scale commercial perovskite solar cells. However, a challenge with the two-step method lies in the incomplete conversion of PbI₂, leading to decreased device performance. To address this issue, potassium L-glutamate (PL-Glu) is introduced to modify the crystal orientation of PbI₂, yielding a perovskite buried interface devoid of any PbI₂ residue. This modification enables better infiltration of FAI, resulting in perovskite films with enhanced crystal quality, thereby significantly reducing the adverse impact of non-radiative recombination caused by the incomplete conversion of PbI₂. Moreover, this method optimizes the energy level structure of the SnO₂ electron transport layer, improving charge transport efficiency at the perovskite/SnO₂ interface. Consequently, n-i-p perovskite solar cells achieve a power conversion efficiency (PCE) of 24.1% with a high fill factor of 82.9%. The PL-Glu-modified device maintained 92% of the initial PCE after 2700 hours under nitrogen. This study provides a novel engineering strategy for simultaneously optimizing perovskite absorbers and interfaces.