A Bi(iii)-based halide with near-unity photoluminescence quantum yield as a blue-light-excited red phosphor for WLEDs

Abstract

In recent years, inorganic–organic hybrid metal halides (IOMHs) have attracted wide attention in the field of white light-emitting diodes (WLEDs) due to their advantages of high-efficiency broadband emission, high photoluminescence quantum yield (PLQY), simple preparation process, etc. In this work, a blue-light-excited red phosphor with near-unity PLQY, namely [BzPPh₃]₂[Bi₂Br₈(bp4do)(DMSO)₂] (denoted as Bz-BiBrON; BzPPh₃⁺ = benzyltriphenylphosphonium, bp4do = 4,4′-bipyridine 1,1′-dioxide, DMSO = dimethyl sulfoxide) was synthesized mechanically. The analysis of the photophysical properties shows that under the excitation of blue light (430 nm), Bz-BiBrON has a broadband emission of 550–800 nm, peaking at 607 nm with a phosphorescence lifetime of 58.43 μs. The PLQY of Bz-BiBrON is up to 90.52%, which is the highest among Bi(III)-based halides. Comparative analysis demonstrates that the modulation of cations in Bi(III)-based halides can help increase their PLQY. With the help of density functional theory calculations, the light absorption-emission mechanism of Bz-BiBrON was elucidated and its broadband red emission was attributed to the phosphorescence of the triplet energy level of the organic ligand bp4do. Bz-BiBrON was used as a red phosphor in a WLED based on blue LED chips, exhibiting a high color rendering index (CRI) of 90.3 and a lumen efficiency of 68.94 lm W⁻¹, which proves the great potential of Bi-IOMHs as the phosphor for WLEDs.