Journal Article

Metal halide perovskite light-emitting diodes (LEDs) are transformative optoelectronic platforms due to their tunable emission, high color purity, and broad color gamut. Nevertheless, the realization of high-luminance blue LEDs, particularly in the deep-blue spectral region, remains challenging compared to their green and red counterparts. This disparity is primarily attributed to the impaired charge transport kinetics and severe nonradiative recombination, both induced by the structural defects in wide-bandgap perovskites. Here, we address this issue through in situ growth of deep-blue-emitting perovskite single-crystal thin films (SCTFs). The resulting SCTFs exhibit exceptional crystallographic orientation, long-range structural ordering, and atomic-level smooth surfaces with a root mean square roughness of 109 picometers. In addition, the SCTFs show a low trap density of 6.9 x 1014 per cubic centimeter. These structural advantages translate to a high photoluminescence quantum yield of 48% and suppressed nonradiative recombination, enabling deep-blue LEDs with a maximum electroluminescence luminance of 179 candelas per square meter at 419 nanometers.