Synthesis‐Kinetics of Violet‐ and Blue‐Emitting Perovskite Nanocrystals with High Brightness and Superior Stability toward Flexible Conversion Layer

Abstract The low photoluminescence (PL) efficiency and unstable features of small blue‐emitting CsPbX 3 nanocrystals (NCs) greatly limit their applications in optoelectronics field. Herein, the synergistic and post‐treatment kinetics are studied to create highly bright and anomalous stable violet (peak position of ≈408 nm) and blue (peak position of ∼ 466 nm) emitting perovskite NCs. Ligand and ion exchange mechanism are systematic studied by the evolution of absorption, PL, and fluorescence lifetime to evaluate ligand bonding, defect engineering, and non‐radiative recombination. Didodecyl dimethyl mmonium chloride (DDAC) and CuX 2 post‐synergistic treatment created DDAC‐CsPbCl 3 ‐CuCl 2 and DDAC‐CsPbCl 3 ‐CuBr 2 NCs that remained the phase composition, morphology, and size of CsPbCl 3 NCs. The PL efficiencies are drastically increased to 42 and 85% for violet‐ and blue‐emitting NCs, respectively. The stability test indicated that the NCs enable against various harsh conditions (e.g., ultraviolet light irradiation and heat‐treatment). The NCs retained their initial PL efficiency after 2 months under ambient conditions and UV light irradiation. These NCs also exhibited high stability after heat‐treatment at 120 °C. The emitting NCs embedded in flexible films still revealed bright PL and high stability, suggesting current results provide a new avenue for the application in the field of optoelectronics.