Synergetic Effect of Ligand Removal, Reparation, and Surface Encapsulation of Cspbbr3 Quantum Dots with Improved Brightness and Stability

Abstract

Colloidal CsPbBr3 perovskite quantum dots (PQDs) are promising optoelectronic materials for use in solution-processed photoelectric devices. However, fabricating PQD thin films with high efficiency and good stability is still challenging. In this study, we investigate the synergetic effects of ligand removal using MeOAc washing, defect repair using cesium acetate (CsAc), and surface encapsulation using hexamethyldisilazane (HMDS) on the photoluminescence (PL) intensity and ambient stability of PQD thin films. The PL intensity is significantly improved by ligand removal and defect repair, and ambient stability is governed primarily by the SiO passivation process. However, the synergetic effect of these post-treatments is also important; the highest PL intensity and the best ambient stability are observed for the sample treated by all three post treatments in the proper order. The PL intensity is enhanced by a factor of up to 3.4, and the ambient instability is reduced by approximately 40 % compared with that of the untreated sample. Defect repair using CsAc is achievable only after the ligand is completely removed. Thus, these results provide essential information and an approach for post-treatments to obtain PQD films with high efficiency and robust stability.

Keywords: Perovskite Quantum Dot, encapsulation, surface passivation, stability, thin films