Thermal-Regulated Crystal Directional Growth for Efficient Sn-Based NIR-II Perovskite Light-Emitting Diodes

Tin-based perovskite light-emitting diodes (Sn-PeLEDs) are ideal for second near-infrared (NIR-II, 900-1800 nm) applications due to their tunable bandgap and environmental friendliness. However, they suffer from defect-induced non-radiative recombination and unbalanced charge transport. Here, we report a thermal-regulated directional crystal growth strategy that controls perovskite crystallization through precise modulation of annealing temperatures. Increasing annealing temperature transforms crystal growth orientation from in-plane lateral to out-of-plane vertical, effectively suppressing grain boundary defects while improving charge carrier balance. The optimized CsSnI₃ films exhibit significantly enhanced optoelectronic properties, enabling the fabrication of high-performance all-inorganic Sn-PeLEDs with 955 nm emission in the NIR-II window. The resulting devices achieve an external quantum efficiency of 7.87%, representing a nearly threefold improvement over conventional preparations, along with excellent operational stability of T₅₀ = 14.16 h at 50 mA cm^-2. This work establishes annealing temperature as a critical parameter for controlling perovskite crystallization dynamics, providing a component-free approach for high-performance NIR-II optoelectronics.​.