High luminous efficiency and Ultra-Stable CsPbBr3@CsPb2Br5:Sr core-shell microplate for white light emitting diodes

Abstract

CsPbX3 (X = Br, Cl, and I) perovskite quantum dots (QDs) have become promising materials for phosphors and solar cells due to their remarkable photovoltaic properties. However, the high defect density and sensitivity to the surrounding environment have hindered the commercial application of the materials in the field of optoelectronics. Core-shell structures have been proved to be an effective method for passivating surface defects and improving stability. However, the complex post-processing tends to dissolve the CsPbX3 QDs, causing the strategy to remain relatively underdeveloped. Here, we present an improved hot-injection method that can facilitate the epitaxial growth of CsPb2Br5 shell on the surface of CsPbBr3 QDs, and, by doping Sr2+ ions to passivate the defects of the QDs, CsPbBr3@CsPb2Br5:Sr core-shell microplates have been obtained. The composites have enhanced optical properties and stability. Density Functional Theory (DFT) calculations show that this is benefited from the introduction of Sr which widens the bandgap of CsPbBr3 and CsPb2Br5, leading to the formation of a quantum well structure between the two, significantly improving the quantum yields of the samples. Finally, the white light emitting diodes prepared using the composite have high luminous efficiency and long-term operational stability.