Monolithic Integration of Redox-Stable Sn–Pb Halide Perovskite Single-Crystalline Films for Durable Near-Infrared Photodetection

Tin-lead (Sn-Pb) halide perovskite single crystals combine narrow bandgaps, long carrier diffusion lengths, and low trap densities, positioning them as ideal candidates for near-infrared (NIR) optoelectronics. However, conventional growth strategies rely on bulk crystallization at elevated temperatures, leading to uncontrolled nucleation, Sn²⁺ oxidation, and poor compatibility with planar integration. Here, we develop a coordination-engineered crystallization strategy that enables direct, low-temperature growth of micrometer-thick Sn-Pb single-crystal thin films on device-compatible substrates. By modulating metal-solvent coordination strength using a low-donor number cosolvent system, we delineate a narrow processing window that stabilizes precursor speciation, lowers the nucleation barrier, and guides directional crystal growth under mild thermal conditions (< 40 °C). The resulting crystal films exhibit smooth morphology, high crystallinity, compositional uniformity, and ultralow trap densities (~ 3.98 × 10¹² cm^-3). When integrated into NIR photodetectors, these films deliver high responsivity (0.51 A W^-1 at 900 nm), specific detectivity up to 3.6 × 10¹² Jones, fast response (~ 188 μs), and > 25,000 cycles of ambient operational stability. This approach establishes a scalable platform for redox-stable, low-temperature growth of Sn-Pb perovskite crystal films and expands the processing-structure-function landscape for next-generation infrared optoelectronics.