Low-temperature annealing stabilizes Sn2+ in tin–lead perovskites via crystallization kinetics for robust near-infrared photodetectors

The photo-oxidation stability of tin–lead hybrid perovskites (TLHPs), arising from the facile Sn2+ oxidation and subsequent phase reconstruction, remains a major obstacle for near-infrared photodetectors (NIR PDs). Here, we demonstrate that low-temperature annealing provides an intrinsic and additive-free route to stabilize TLHPs by regulating crystallization kinetics. This process slows the crystallization of Sn-rich species relative to their Pb-rich counterparts, suppressing Sn accumulation at the bottom interface and forming a Sn-deficient barrier that inhibits initial Sn2+ oxidation. As a result, phase reconstruction and defect formation are effectively suppressed. The optimized PDs deliver a high responsivity of 0.40 A W−1, a specific detectivity of 2.64 × 1012 Jones at 810 nm, and an ultrafast response of 0.40/2.12 μs. Robust operation is further demonstrated in practical NIR applications, including photoplethysmography-based heart-rate monitoring and optical communication at 200 kHz. This work establishes crystallization-kinetics control as a scalable strategy for Sn2+ management, enabling stable and high-performance TLHP optoelectronics.