Enhancement of intrinsic luminescence by Sb3+ doped (C7H9N)2CdBr6 with lone pair 5s2 electrons

Abstract

Metal halides have a wide range of applications in the field of photovoltaics due to their diverse crystal and electronic structures and tunable emission properties. In recent years, organic–inorganic metal halides have received more attention due to their broad emission bands, high luminescence efficiencies, and excessive stability. However, their photoluminescence (PL) mechanisms still need to be further explored. In this work, we have chosen Cd as the metal center to synthesize a stable 2D organic–inorganic metal halide (C₇H₉N)₂CdBr₆ (C₇H₉N = 4-bromobenzylamine cation) and revealed its interesting luminescence properties through experimental studies and density-functional-theory (DFT) calculations. The photoluminescence (PL) of (C₇H₉N)₂CdBr arises from intrinsic self-trapped domain exciton emissions (STEs). Upon the introduction of Sb³⁺ containing lone-pair 5s² electrons, (C₇H₉N)₂CdBr₆ undergoes various changes, including bandgap reduction and structural lattice softening, and the STEs are progressively enhanced, with an increase in the photoluminescence quantum yield from 31.42% to 59.86%. In this work, the luminescence mechanism of Sb³⁺ doped (C₇H₉N)₂CdBr₆ with lone pair 5s² electrons is discussed in detail. An effective strategy is provided for the search for environmentally friendly stabilized organic–inorganic metal halides (OIMHs) and further enhancement of luminescence performance by doping with lone-pair-containing cations.