High defect tolerance β-CsSnI3perovskite light-emitting diodesElectronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4mh00428k

All-inorganic lead-free CsSnI3has 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 CsSnI3-based Pero-LEDs, limiting their potential applications. Here, we uncovered that β-CsSnI3exhibits higher defect tolerance compared to orthorhombic γ-CsSnI3, offering a potential for enhancing the emission efficiency. We further reported on the deposition and stabilization of highly crystalline β-CsSnI3films 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-CsSnI3emitters 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.