Ultrastable, cationic three-dimensional lead bromide frameworks that intrinsically emit broadband white-light.

Chengdong Peng,Honghan Fei,Huimin Yang,Zewen Zhuang,Guiyang Zhang

doi:10.1039/c7sc04118g

Abstract

Herein, we report the unusual broadband white-light emission as an intrinsic property from two cationic lead bromide frameworks. This is the first time that the metal halide materials adopting a purely inorganic positively-charged three-dimensional (3D) topology have been synthesized, thus affording highly distorted PbII centers. The single-component white-light emitters achieve an external quantum efficiency of up to 5.6% and a correlated color temperature of 5727 K, producing typical white-light close to that of fluorescent light sources. Unlike the air/moisture-sensitive 3D organolead halide perovskites, our cationic materials are chemically "inert" over a wide range of pH as well as aqueous boiling condition. Importantly, these long-sought ultrastable lead halide materials exhibit undiminished photoluminescence upon continuous UV-irradiation for 30 days under atmospheric condition (∼60% relative humidity, 1 bar). Our mechanistic studies indicate the broadband emission have contributions from the self-trapped excited states through electron-vibrational coupling in the highly deformable and anharmonic lattice, as demonstrated by variable-temperature photoluminescence/absorption spectra as well as X-ray crystallography studies. The chemical robustness and structural tunability of the 3D cationic bromoplumbates open new paths for the rational design of hybrid bulk emitters with high photostability.

Highlights

Solid-state lighting, an energy-saving alternative technology to conventional lighting sources, has attracted increasing attention in recent years.[1]
A typical whitelight light-emitting diodes (LEDs) device includes a blend of red, green and blue (RGB) LEDs or coating a blue LED with a yellow phosphor.[5,6,7]. These multi-color and/or multi-component strategies suffer from a variety of inevitable drawbacks, such as efficiency losses arising from selfabsorption and long-term instability due to different degradation rates of the phosphors.[8,9]
We reported a class of 2D cationic lead halide materials with high chemical resistance and high photoluminescence quantum efficiency.[47]

Summary

Introduction

Solid-state lighting, an energy-saving alternative technology to conventional lighting sources, has attracted increasing attention in recent years.[1]. The temperature-dependent photophysical studies (e.g. UV-vis absorption spectra and photoluminescence spectra) and X-ray crystallography studies attribute the broad emission to the self-trapped states from electron-vibrational coupling in the strongly deformable and anharmonic lattice.

Results

Conclusion