Enhanced intrinsic white-light emission upon near-UV excitation by crystal engineering of cationic lead bromide layered materials

Abstract

Corrugated lead halide 2D perovskites are an emerging class of intrinsic broadband white-light emitters. Recently, we reported first-generation ultrastable cationic lead halide emitters, overcoming the air/moisture sensitivity of perovskites. Herein, the crystal engineering of cationic lead bromide layers realized a 4-fold improvement of photoluminescence quantum efficiency (PLQE) over our previous materials. The PLQE is stepwise increased by enhancing the structural deformation from inorganic slabs as well as the quantum confinement effect from organic pillaring spacers. Upon continuous near-UV irradiation (>360 nm) under atmospheric conditions, [Pb₄Br₆][O₂C(CH₂)₆CO₂] exhibits undiminished broadband photoemission with a PLQE of 8.2% for at least 30 days. Variable-temperature photophysics studies and density functional theory calculations indicate the enhanced PLQE is largely attributed to the formation of self-trapped excitons (Pb₂³⁺ and Br₂⁻) originating from strong electron–phonon coupling in cationic bromoplumbate layers.