Unravelling the structure–luminescence relationship in two dimensional antimony(iii)-doped cadmium(ii) halide hybrids†

Luminescent zero dimensional (0D) antimony halide (Sb–X) hybrids showcase emissive properties (emission peak position; photoluminescence quantum yield – PLQY) that are strongly dependent on the local metal halide geometry/site asymmetry. However, controlling the local metal halide geometry has been synthetically challenging due to the diverse coordination geometries adopted by the Sb–X units. Consequently, efforts ascertaining a clear structure–luminescence relation in 0D Sb–X hybrids have met with limited success. Reported here is an attempt to draw a structure–luminescence relationship by controlling the Sb–X geometry utilizing 2D cadmium halide hybrids as the host that serves as a framework for incorporating emissive Sb³⁺ dopants. The choice of a series of organic cations tunes the local metal halide geometry/distortion in the host hybrids that controllably alters the luminescent properties of the emissive dopants in 2D Sb³⁺ doped hybrids. A clear structure–luminescence relationship is observed: red-shifted emission peak positions and enhanced PLQYs as the extent of the local metal halide distortion increases. DFT calculations of the doped compounds, characterizing ground and excited state structural and electronic properties, reveal the operative luminescence mechanism and the origin of different efficiency of luminescence (PLQY). This work provides deeper insight into the luminescence mechanism highlighting the importance of ground and excited state structural distortions in Sb³⁺ doped 2D cadmium halide hybrids. The experimental–computational insights gained here are beneficial for establishing the structure–luminescence relationship for 0D Sb halide hybrids targeting their rational synthesis.