Low-Temperature fabrication of CsPbI3@PVA films for Ultra-Stable Down-Conversion white Light-Emitting Diodes: From molecular interactions to phase stability

Perovskite nanocrystals (NCs) are sparking intensive interest in display applications, due to their universal and unique merits such as exceptional color purity, tunable emission, and high efficiency. Unfortunately, their intrinsically unstable emission in the red part of the spectrum, mainly attributed to high formation energy barriers and undesired phase transitions significantly challenges their potential applications. Herein, we present a low-temperature (down to 50 °C) and aqueous-solvent process for the in-situ growth of γ -CsPbI 3 perovskite NCs in the polyvinyl alcohol (PVA) composite films. Introduced PVA was demonstrated to reduce the forming energy to lower the reaction temperature by forming [PbI 6 ] 4- @PVA complexes as well as to bond with CsPbI 3 preventing its transition to a non-luminous phase, thus enabling fundamentally enhanced stability. The resultant CsPbI 3 @PVA films exhibit highly efficient red photoluminescence (PL) at 686 nm, with a full width at half-maximum of 37 nm and quantum yield up to 91%, respectively. Moreover, the films demonstrate superb stability, which retains 97% initial PL intensity after 1000 hours of aging at 80 °C and blue-light exposure at 460 nm and 13 mW cm −2 . The as-assembled white light-emitting device achieves a T 95 lifetime up to 240 hours at 200000 cd/m −2 , underscoring their promise for commercial lighting and display applications.