Surface passivation of halide perovskite nanocrystals for stable and high purity color conversion

Abstract

Surface passivation using aminopropyl-functionalized siloxane is proposed via a post-synthesis ligand exchange reaction. The near-unity photoluminescence quantum yield (PLQY) is explained by more efficient surface passivation, which is confirmed by transient PL measurements. Alternatively, the siloxane can be introduced during the hot-injection synthesis, and a thicker SiO2 shell structure is formed on the surface of nanocrystals (NCs), which leads to agglomeration and degrades optical properties. The low-temperature ligand exchange reaction lends precision process control; thereby, an optimized PLQY of 99% is achieved. Moreover, the emission wavelength of the siloxane passivated CsPbBr3 can be modulated via halide exchange for highly saturated and stable green emissions. The stability of these NCs is first ascribed to the siloxane moiety. Siloxane passivated CsPbI3 NCs were also prepared with bright red emission. A wide color gamut of 134.9% National Television System Committee or 100.7% Rec. 2020 is realized using blue light-emitting diodes together with green and red perovskite NCs. We stress the effect of Cs vacancy repair via the ligand exchange and the essentially monolayer thickness of the ligand shell to ascribe the high performance of these NCs.