Strong Self-Trapped Exciton Emissions in Two-Dimensional Na-In Halide Perovskites Triggered by Antimony Doping

Soft lattice and strong exciton-phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self-trapped exciton (STE) emitters for applications in solid-state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three-dimensional (3D) Cs2NaInCl6, we synthesized two 2D derivatives (PEA)(4)NaInCl8:Sb (PEA=phenethylamine) and (PEA)(2)CsNaInCl7:Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb-doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first-principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl6](3-) octahedron.

Automated summary

Layered double perovskites (LDPs) have shown strong exciton-phonon coupling and soft lattice, making them promising candidates for solid-state lighting applications. By synthesizing two 2D derivatives with excellent self-trapped exciton (STE) emissions, (PEA)(4)NaInCl8:Sb and (PEA)(2)CsNaInCl7:Sb, the photoluminescence quantum efficiency (PLQE) reached 48.7% and 29.3% respectively, surpassing current known LDPs. The broadband emissions originate from trapped STEs at the introduced [SbCl6](3-) octahedron, as indicated by spectroscopic characterizations and first-principles calculations.