Influence of Lewis basicity on the S ²⁻ induced synthesis of 0D Cs ₄ PbBr ₆ hexagonal nanocrystals and its implications for optoelectronics

Perovskite nanocrystals (NCs) with their excellent optical and semiconductor properties have emerged as primary candidates for optoelectronic applications. While extensive research has been conducted on the 3D perovskite phase, the zero-dimensional (0D) form of this promising material in the NC format remains elusive. In this paper, a new synthesis strategy is proposed. According to the Hard-Soft Acid-Base (HSAB) principle, a novel class of hexagonal semiconductor nanocrystals (Cs₄PbBr₆ HNCs) derived from 0D perovskite Cs₄PbBr₆ is synthesized by doping an appropriate amount of PbS precursor solution into bromide. These Cs₄PbBr₆ HNCs are characterized and compared in detail to CsPbBr₃ cubic nanocrystals (CsPbBr₃ CNCs) as a reference. The Cs₄PbBr₆ HNCs exhibit significantly enhanced photoluminescence (PL) compared to CsPbBr₃ CNCs, with an external quantum efficiency (EQE) reaching 24.19%. Furthermore, they demonstrate superior UV stability compared to CsPbBr₃ CNCs. Comparative analysis of their physical properties and morphology, along with detailed investigations into band structures, density of states, and lifetime decay through DFT calculations, is provided. The practical application potential is validated by encapsulating them into backlight LEDs, covering 121.5% and 90.7% of the color gamut of NTSC and Rec. Our research provides comprehensive insights into the photophysical properties of inorganic halide perovskite nanomaterials and explores their potential in the field of optoelectronics.