High defect tolerance β-CsSnI 3 perovskite light-emitting diodes.

All-inorganic lead-free CsSnI 3 has shown promising potential in optoelectronic applications, particularly in near-infrared perovskite light-emitting diodes (Pero-LEDs). However, non-radiative recombination induced by defects hinders the optoelectronic properties of CsSnI 3 -based Pero-LEDs, limiting their potential applications. Here, we uncovered that β-CsSnI 3 exhibits higher defect tolerance compared to orthorhombic γ-CsSnI 3 , offering a potential for enhancing the emission efficiency. We further reported on the deposition and stabilization of highly crystalline β-CsSnI 3 films with the assistance of cesium formate to suppress electron-phonon scattering and reduce nonradiative recombination. This leads to an enhanced photoluminescence quantum yield up to ∼10%. As a result, near-infrared LEDs based on β-CsSnI 3 emitters are achieved with a peak external quantum efficiency of 1.81% and excellent stability under a high current injection of 1.0 A cm -2 .