Ultrathin, Friendly Environmental, and Flexible CsPb(Cl/Br)₃-Silica Composite Film for Blue-Light-Emitting Diodes

Due to intrinsic defects in blue-light-emitting perovskite materials, the charge carriers are prone to being trapped by the trap states. Therefore, the preparation of efficient blue-light-emitting perovskite materials remains a significant challenge. Herein, CsPb(Cl/Br)₃ nanocrystal (NCs)@SiO₂ structures were fabricated through hydrolyzing (3-aminopropyl)-triethoxysilane (APTS). SiO₂ can passivate the surface trap states of NCs, suppress the nonradiative recombination pathways of NCs, and effectively stabilize the surface of NCs. CsPb(Cl/Br)₃ NCs@SiO₂ exhibits higher photoluminescence (PL) intensity and lifetime compared to those of the pure CsPb(Cl/Br)₃ NCs. The enhancement of the exciton binding energy (<i>E</i>_b) leads to increased PL intensity and lifetime in CsPb(Cl/Br)₃ NCs @SiO₂, as demonstrated by temperature-dependent PL spectra. Subsequently, a 0.3 mm film of CsPb(Cl/Br)₃ NCs@SiO₂/poly(methyl methacrylate) (PMMA) was fabricated through optimizing the casting method. Due to the effective protection provided by SiO₂ and PMMA, CsPb(Cl/Br)₃ NCs@SiO₂/PMMA film exhibits excellent thermal, water, and air stability. Moreover, the CsPb(Cl/Br)₃ NCs@SiO₂/PMMA film also exhibits good flexibility, maintaining the PL intensity unchanged under bending conditions. Importantly, lead can be well encapsulated in SiO₂ and PMMA, effectively preventing lead from leaking into the environment. This research demonstrates the potential of a CsPb(Cl/Br)₃ NCs@SiO₂/PMMA film for applications in the friendly environmental field of optoelectronics, including light-emitting diodes (LEDs) and flexible displays.