Simultaneous Defect Passivation and Crystallization Kinetics Regulation of Perovskite Thin Films Using a Nitro-Rich Additive for Efficient Inverted Solar Cells.

Abstract

Metal halide perovskite solar cells are fundamentally limited by uncontrollable crystallization kinetics during film formation and defect-induced non-radiative recombination. To address this challenge, 4-Chloro-3,5-dinitrobenzotrifluoride (CNBF) is designed and introduced to simultaneously achieve precise regulation of the crystallization pathway and chemical passivation of defects. The nitro group (─NO2) in the CNBF molecule acts as a strong Lewis base site, coordinating strongly with Pb2+, thereby effectively modulating film crystallization and passivating deep-level trap states. In situ GIWAXS reveals that CNBF significantly accelerates the transformation from the photo-inactive δ-phase to the photoactive α-phase. Benefiting from the optimized crystallization kinetics, the CNBF-modified film exhibits an increased grain size from 400 nm to 640 nm, reduced surface roughness, and the formation of a single-grain structure throughout the entire film thickness. Optical characterization shows substantially enhanced PL intensity and prolonged carrier lifetime, indicating effective suppression of non-radiative recombination. Consequently, the CNBF-modified inverted PSC achieves a champion PCE of 25.66%. Furthermore, the device retains 86.21% of its initial efficiency after storage under high humidity and elevated temperature for 1200 h.