Self-trapped Exciton Emission based on Halogen-substituted Metal Halides

Recently, organic-inorganic hybrid metal halides (OIHMs) have been effective white light emitters. Still, the toxicity and instability of lead halides limit their applications. Sb has a relatively similar structure to Pb making it a better substitution. In this work, we synthesized zero-dimensional antimony-based OIMHs (BTBAC)2SbCl5 and (BTBAB)2SbBr5 [BTBA+ (BTBA+ = benzyl tributyl ammonium ion)]. The chloride photoluminescence quantum yield (PLQY) is 72.69% and that of bromide is 17.33%. Spectral tunability from red to yellow is observed after halogen substitution. Density-functional theory (DFT) calculations show that halogens change the bandgap structure from (BTBAC)2SbCl5 direct bandgap to (BTBAB)2SbBr5 indirect bandgap. In addition, (BTBAC)2SbCl5 has excellent thermal stability at 455.15 K and optical properties with strong electron-phonon coupling producing broadband self-trapped exciton (STE) emission. By mixing (BTBAC)2SbCl5 with a commercial phosphor, a white LED with a color rendering index of 87 was created. We have demonstrated the photoluminescence properties of OIMH materials in terms of the series of halogen atoms. This work injects new innovative ideas for the design of novel photoluminescent materials.