High Color Rendering Index White-Light Emission from UV-Driven LEDs Based on Single Luminescent Materials: Two-Dimensional Perovskites (C₆H₅C₂H₄NH₃)₂PbBr<i>_x</i>Cl_4–<i>x</i>

Two-dimensional (2D) white-light-emitting hybrid perovskites (WHPs) are promising active materials for single-component white-light-emitting diodes (WLEDs) driven by UV. However, the reported WHPs exhibit low quantum yields (≤9%) and low color rendering index (CRI) values less than 85, which does not satisfy the demand of solid-state lighting applications. In this work, we report a series of mixed-halide 2D layered WHPs (C₆H₅C₂H₄NH₃)₂PbBr<i>_x</i>Cl_4–<i>x</i> (0 < <i>x</i> < 4) obtained from the phenethylammonium cation. Unlike the reported WHPs including (C₆H₅C₂H₄NH₃)₂PbCl₄, the mixed-halide perovskites display morphology-dependent white emission for the different extents of self-absorption. Additionally, the amount of Br has a huge influence on the photophysical properties of mixed-halide WHPs. With the increasing content of Br, the quantum yields of WHPs increase gradually from 0.2 to 16.9%, accompanied by tunable color temperatures ranging from 4000 K (“warm” white light) to 7000 K (“cold” white light). When applied to the WLEDs, the mixed-halide perovskite powders exhibit tunable white electroluminescent emission with very high CRI of 87–91

High Performance and Enhanced Durability of Thermochromic Films Using VO₂@ZnO Core–Shell Nanoparticles

For VO₂-based thermochromic smart windows, high luminous transmittance (<i>T</i>_lum) and solar regulation efficiency (Δ<i>T</i>_sol) are usually pursued as the most critical issues, which have been discussed in numerous researches. However, environmental durability, which has rarely been considered, is also so vital for practical application because it determines lifetime and cycle times of smart windows. In this paper, we report novel VO₂@ZnO core–shell nanoparticles with ultrahigh durability as well as improved thermochromic performance. The VO₂@ZnO nanoparticles-based thermochromic film exhibits a robust durability that the Δ<i>T</i>_sol keeps 77% (from 19.1% to 14.7%) after 10³ hours in a hyperthermal and humid environment, while a relevant property of uncoated VO₂ nanoparticles-based film badly deteriorates after 30 h. Meanwhile, compared with the uncoated VO₂-based film, the VO₂@ZnO-based film demonstrates an 11.0% increase (from 17.2% to 19.1%) in Δ<i>T</i>_sol and a 31.1% increase (from 38.9% to 51.0%) in <i>T</i>_lum. Such integrated thermochromic performance expresses good potential for practical application of VO₂-based smart windows