Wavelength-tunable deep blue emission from pure bromide-based colloidal perovskite nanocrystals

Metal halide perovskites are promising light emitters due to their tunable and highly pure emission color in visible light. However, achieving deep blue emission remains a major challenge due to low stability and intrinsic defects. Traditional methods for synthesizing blue-emitting colloidal perovskite nanocrystals (PNCs) involve organic ammonium engineering and halide engineering, which often suffer from problems such as ion migration and color instability. In this study, we demonstrate a novel central metal engineering approach that achieves deep blue emission with a wavelength of 435.8 nm from pure bromide-based PNCs at room temperature. To synthesize deep blue-emitting pure-bromide-based PNCs, we incorporate manganese bromide (MnBr₂) to the formamidinium-guanidinium lead bromide (FA_0.9GA_0.1PbBr₃) PNCs. Mn²⁺ suppresses the growth of FA_0.9GA_0.1PbBr₃ crystals during the synthesis, resulting in decreases in both particle size and dimensionality and deep blue emission by the quantum confinement effect. The emission wavelength of pure-bromide-based PNCs is controlled by varying the amount of MnBr₂. This study provides an effective and simple method for achieving deep blue emission from pure bromide-based PNCs, offering significant advantages for display technologies such as light-emitting diodes.