Crystallization kinetics regulation of lead-tin-mixed perovskite with fully developed micron-scale pre-nucleation clusters for high-performance near-infrared photodetectors

The crystallization dynamics of lead-tin perovskites play a critical role in determining film quality and optoelectronic performance, yet the rapid crystallization rate induced by tin incorporation complicates the nucleation and growth processes of perovskite. With a focus on understanding the role of pre-nucleation clusters (PNCs) in precursor dispersion, we herein find that the particle size of fully developed micron-scale PNCs, under non-classical nucleation theory, is closer to the critical nucleation size, thereby lowering the nucleation barrier. Compared to partially aggregated pre-nucleation clusters (PAPNCs), PNCs exhibit a uniform distribution and larger dimensions, as confirmed by small angle X-ray scattering (SAXS) and dynamic light scattering (DLS) analyses, which reduce colloidal heterogeneity and bring the nanoparticle in precursor dispersion closer to the critical nucleation size. This promotes consistent nucleation, accelerates crystallization, and results in compact, pinhole-free films with enhanced crystallinity, reduced trap densities, and prolonged carrier lifetime. These improvements lead to superior near-infrared photodetector performance, achieving a detectivity of 2.54 × 10¹² Jones and a responsivity of 0.56 A/W under 940 nm NIR illumination. This work highlights the critical impact of uniformly distributed large size PNCs on tailoring crystallization dynamics and advancing the performance of perovskite-based optoelectronic devices.