Pressure-Synergistic Ligand Engineering Toward Enhanced Emission and Remarkable Piezochromism in Cadmium Sulfide Nanocrystals

Abstract

Challenge of passivating defects to harvest the high-efficiency emission in semiconductor materials significantly limit their practical applications in solid-state lighting. Here, a robust strategy is developed through pressure-synergistic ligand engineering to achieve enhanced emission and remarkable piezochromism in the synthesized cadmium sulfide (CdS) nanocrystals (NCs) that exhibits both band-edge (BE) emission and strong defect emission. With increasing pressure, the CdS NCs experienced a piezochromism from orange emission to white emission. Note that by introducing additional ligand of cadmium oleate, a marked transition is achieved in emission color from orange to blue–violet with high color purity of 71.4% under high pressure. Furthermore, through the pressure-enhanced defect passivation with capping ligand, the CdS NCs realized a considerable BE emission enhancement, accompanied by the gradually decreased defect emission. In situ high-pressure experiments and first-principles calculations indicate that the interaction between ligand and CdS NCs is indeed enhanced under high pressure, thus facilitating the defects passivation and ultimately leading to the observed piezochromism and emission enhancement. This study endows high pressure as an efficient tool to enhance the surface defect passivation, paving the way for precise control over piezochromism and high-efficiency emission through materials design.