Designing guanidine-based lead-free hybrid indium perovskites with highly efficient intrinsic broadband emissions

Abstract

Recent advances in luminescent materials have highlighted zero-dimensional (0D) hybrid metal halides as highly efficient candidates. Notably, In³⁺-based organic–inorganic metal halides (OIMHs) are increasingly recognized as promising materials for solid-state light emission. However, the relatively low light yields of these materials significantly limit their application in advanced optoelectronic devices. In this study, we designed a novel 0D hybrid indium halide, (C₁₃H₁₄N₃)₃InBr₆, where C₁₃H₁₄N₃ represents 1,3-diphenylguanidine. This compound features a structure in which the halogen anionic polyhedron is completely isolated by large guanidine cations and is regularly arranged at considerable distances on these cations, thus forming an almost ideal host–guest structure. Impressively, the 0D indium halide exhibits intrinsic broadband yellow-orange light emission, achieving a photoluminescence quantum yield (PLQY) of 86.12%, which is the highest PLQY ever reported for In-based OIMHs. Additionally, we successfully fabricated white-light-emitting diodes (WLEDs) using (C₁₃H₁₄N₃)₃InBr₆ as a yellow phosphor, thereby demonstrating the potential of novel guanidine-based indium halides in solid-state lighting applications.