Highly efficient blue luminescence from stable lead-free Cu-doped Rb2LiBiBr6 double perovskites

Abstract

Highly efficient three-dimensional (3D) lead-free halide perovskites that produce blue light emission with outstanding stability have attracted global research attention. In order to increase the light emission efficiency of Rb2LiBiBr6 perovskites, band structure engineering can be performed by doping Cu2+ ions. In this work, the structural, chemical and optical characteristics of pure Rb2LiBiBr6 (RLBB) and Cu2+-doped Rb2LiBiBr6 (RLBBC) phosphors produced through conventional wet chemical processes are reported. A narrow and comparatively unique blue emission was exhibited by Cu2+-doped Rb2LiBiBr6 double perovskites (DPs) as a result of electron-phonon interactions. The phase purity and microstructure of the Rb2LiBiBr6:Cu2+ DP were assessed using X-ray diffraction and scanning electron microscopy, respectively. All the synthesized samples showed a orthorhombic crystal structure, and B sites had a substantial impact on the Pnma space group in the Rb2LiBiBr6 DP framework. The Bi3+ ions at the B ' sites were replaced by the doped Cu2+ ions, which distributed themselves to an equilibrium valence state and showed minimal variation in the ionic radius. Photoluminescence (PL) spectra were used to explore the corresponding mechanism of the Cu2+ -> Bi3+ energy-transfer process. The Cu2+-doped Rb2LiBiBr6 (RLBBC) phosphors exhibited a blue emission at 469 nm when excited at 367 nm. It showed an optical bandgap of 2.87 eV at room temperature. This as-prepared perovskite showed outstanding stable chromaticity with (x,y) coordinate values of (0.1367, 0.0596) under a continuous irradiation of 367 nm UV light. This lead-free and highly effective Cu2+-Rb2LiBiBr6 DP has a wide range of applications in the rarest blue photonic and optoelectronic domains as it demonstrates the potential to overcome the obstacles of extreme toxicity and inadequate stability.