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

ABSTRACT 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 CsSnI 3 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 T 50 = 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.​