Ultrabright near-infrared lead-free perovskite light-emitting diodes with negligible efficiency roll-off

Lead-free halide perovskite semiconductors show great promise for light-emitting diodes (LEDs), benefiting from tunable optoelectronic properties and solution processability. However, their practical applications in high-current-density LEDs are fundamentally constrained by severe efficiency roll-off, primarily caused by non-radiative recombination and carrier-induced structural instabilities. In this study, we introduce a molecular N,N′-diphenylthiourea (DPTA) engineered tin perovskite semiconductor (CsSnI3) that achieves photoluminescence quantum efficiency (PLQE) of 36% at a carrier concentration of 1018 cm-3. Our approach involves a strategy to precisely control charge carrier concentration and lattice growth. High resolution transmission electron microscopy further demonstrates that the uniform local strain distribution in lattice from doped films enhances carrier wavefunction overlap, leading to a substantial boost in PLQE. Leveraging the enhanced optoelectronic properties of DPTA-doped CsSnI3, we fabricate near-infrared LEDs that exhibit an external quantum efficiency (EQE) of 13.4% and an unprecedented peak radiance of 1248 W sr-1 m-2, with minimal efficiency roll-off even at high current densities exceeding 3500 mA cm-2 in the pulse-mode operation. This work introduces a new material doping strategy for lead-free perovskites, demonstrating their potential for high-power optoelectronic applications and advancing the feasibility of electrically pumped perovskite laser diodes.