Engineering Green-to-Blue Emitting CsPbBr₃ Quantum-Dot Films with Efficient Ligand Passivation

A series of challenging issues such as field-driven spectral drift for the CsPbClxBr3–x system and mixed phases in quasi-two-dimensional structures still exist when devising blue-emitting perovskites. In this Letter, the CsPbBr3 quantum-dot (QD) system is proposed to overcome these challenges. However, to date, the CsPbBr3 QD films with tunable colors from green to blue still cannot be achieved using existing methods. Herein, a simple one-step spin-coating route incorporated with efficient ligand passivation is developed to realize this goal. The size restriction of CsPbBr3 QDs is enabled by a diammonium ligand, propane-1,3-diammonium bromide (PDAB). A mixed-ligand system of phenethylammonium bromide (PEAB) with PDAB is further explored to enhance their optical performance. The CsPbBr3 QDs experience a second growth process upon controlled air exposure, which is utilized to realize their size control and emission wavelength tunability. The CsPbBr3 QD-based devices exhibit no spectral drift in electroluminescence under voltage bias.