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 CsPbCl x Br 3– x system and mixed phases in quasi-two-dimensional structures still exist when devising blue-emitting perovskites. In this Letter, the CsPbBr 3 quantum-dot (QD) system is proposed to overcome these challenges. However, to date, the CsPbBr 3 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 CsPbBr 3 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 CsPbBr 3 QDs experience a second growth process upon controlled air exposure, which is utilized to realize their size control and emission wavelength tunability. The CsPbBr 3 QD-based devices exhibit no spectral drift in electroluminescence under voltage bias.