Ultrathin,\nFriendly Environmental, and Flexible CsPb(Cl/Br)<sub>3</sub>‑Silica\nComposite Film for Blue-Light-Emitting Diodes

Due to intrinsic defects in blue-light-emitting perovskite\nmaterials,\nthe charge carriers are prone to being trapped by the trap states.\nTherefore, the preparation of efficient blue-light-emitting perovskite\nmaterials remains a significant challenge. Herein, CsPb(Cl/Br)<sub>3</sub> nanocrystal (NCs)@SiO<sub>2</sub> structures were fabricated\nthrough hydrolyzing (3-aminopropyl)-triethoxysilane (APTS). SiO<sub>2</sub> can passivate the surface trap states of NCs, suppress the\nnonradiative recombination pathways of NCs, and effectively stabilize\nthe surface of NCs. CsPb(Cl/Br)<sub>3</sub> NCs@SiO<sub>2</sub> exhibits\nhigher photoluminescence (PL) intensity and lifetime compared to those\nof the pure CsPb(Cl/Br)<sub>3</sub> NCs. The enhancement of the exciton\nbinding energy (<i>E</i><sub>b</sub>) leads to increased\nPL intensity and lifetime in CsPb(Cl/Br)<sub>3</sub> NCs @SiO<sub>2</sub>, as demonstrated by temperature-dependent PL spectra. Subsequently,\na 0.3 mm film of CsPb(Cl/Br)<sub>3</sub> NCs@SiO<sub>2</sub>/poly(methyl\nmethacrylate) (PMMA) was fabricated through optimizing the casting\nmethod. Due to the effective protection provided by SiO<sub>2</sub> and PMMA, CsPb(Cl/Br)<sub>3</sub> NCs@SiO<sub>2</sub>/PMMA film\nexhibits excellent thermal, water, and air stability. Moreover, the\nCsPb(Cl/Br)<sub>3</sub> NCs@SiO<sub>2</sub>/PMMA film also exhibits\ngood flexibility, maintaining the PL intensity unchanged under bending\nconditions. Importantly, lead can be well encapsulated in SiO<sub>2</sub> and PMMA, effectively preventing lead from leaking into the\nenvironment. This research demonstrates the potential of a CsPb(Cl/Br)<sub>3</sub> NCs@SiO<sub>2</sub>/PMMA film for applications in the friendly\nenvironmental field of optoelectronics, including light-emitting diodes\n(LEDs) and flexible displays.