High
Color Rendering Index White-Light Emission from UV-Driven LEDs Based
on Single Luminescent Materials: Two-Dimensional Perovskites (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<i><sub>x</sub></i>Cl<sub>4–<i>x</i></sub>
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Abstract
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 (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<i><sub>x</sub></i>Cl<sub>4–<i>x</i></sub> (0 < <i>x</i> <
4) obtained from the phenethylammonium cation. Unlike the reported
WHPs including (C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub>)<sub>2</sub>PbCl<sub>4</sub>, 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
