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

Metal halides have a wide range of applications in the field of photovoltaics due to their diverse crystal, electronic structures and tunable emission properties. In recent years, organic-inorganic metal halides have paid 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 the 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 (STE) emission. Upon the introduction of Sb3+ containing lone-pair 5s2 electrons, (C7H9N)2CdBr6 undergoes various changes, including bandgap reduction and structural lattice softening, and the self-trapped domain exciton emission (STEs) is 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 electron is discussed in detail. An effective strategy is provided for the search of environmentally friendly stabilized OIMHs and further enhancement of luminescence performance by doping with lone-pair-containing cations.