Sulfate-Passivated\nCsPbI₃ Perovskite Nanocrystals\nfor Efficient Red Light-Emitting Diodes

Abstract

Due to their excellent optical performance, lead halide\nperovskite\nnanocrystals (PeNCs) have been widely used in optoelectronic devices.\nHowever, the presence of surface defects such as localized trap states\nseverely hampers their practical application in optoelectronic fields.\nIn this work, we have developed a simple method to reduce surface\ndefects by introducing sulfuric acid after the nucleation of CsPbI₃ PeNCs is complete. Sulfate ions effectively interact with\nthe exposed metal lead ions on the surface of perovskite NCs, leading\nto surface passivation. This process represses nonradiative recombination\nand significantly enhances the luminescence efficiency of PeNCs. Moreover,\nthe passivated CsPbI₃ PeNCs with SO₄^2– exhibit a lower overall energy-level structure compared to that\nof pristine CsPbI₃ PeNCs, promoting improved electron injection.\nBenefiting from this highly effective passivation strategy, light-emitting\ndiodes (LEDs) based on SO₄^2–-passivated\nPeNCs exhibit an optimal external quantum yield of 9.94% and luminance\nof 2182 cd m^–2, surpassing the performance of LEDs\nmade from pristine PeNCs.