High-efficiency, long-lived lead-free perovskite light-emitting diodes.

Tin halide perovskite light-emitting diodes (PeLEDs) offer promise due to their solution processability and low toxicity, yet low efficiency and poor stability hinder practical use. We found that electroluminescence failure in CsSnI3 is primarily driven by excessive hole injection-triggered electrochemical Sn2+ oxidation and an irreversible phase transition to Cs2SnI6. Through a dual-side optimization strategy combining formamidine doping with triphenylphosphine oxide modification to stabilize the perovskite lattice, suppress nonradiative recombination, and balance carrier transport, we demonstrate highly efficient near-infrared PeLEDs. These lead-free devices achieve a peak external quantum efficiency of 21.2% at 963 nanometers and a maximum radiance of 195.8 watts per steradian per square meter (W sr-1 m-2). Notably, the operating half-lifetime reaches 920.5 hours at 7.1 W sr-1 m-2, providing pathways for high-performance lead-free PeLEDs.