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

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 photophysical properties shows that under the excitation of blue light (430 nm), Bz-BiBrON has a broadband emission of 550 nm-800 nm, peaking at 607 nm with 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 analyis demonstates 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 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.