Layered halide perovskites and double perovskites optoelectronic properties have recently been the subject of intense research. Layered double perovskites represent the merging of both worlds, and as such, have the potential to further expand the already vast space of optoelectronic properties and applications of halide perovskites. Despite having more than 40 known members, to date, only the <111>-oriented layered double perovskites: Cs4Cd1–xMnxBi2Cl12, have shown efficient photoluminescence (PL). In this work, we replaced Bi with Sb to further investigate the electronic structure and PL properties of these materials, resulting in two new families of layered inorganic perovskites alloys with full solubility. The first family, Cs4Cd1–xMnSb2Cl12, exhibits a PL emission at 605 nm ascribed to Mn2+ centers in octahedral coordination, and a maximum photoluminescence quantum yield PLQY of 28.5%. The second family of alloys, also with full solubility, Cs4Cd0.8Mn0.2(Sb1–yBiy)2Cl12, contains a fixed amount of Mn2+ and Cd2+ cations but different concentrations of the trivalent metals. This variability allows the tuning of the PL emission from 603 nm to 614 nm. We show that the decreased efficiency of the Cs4Cd1–xMnxSb2Cl12family compared to Cs4Cd1–xMnxBi2Cl12, is mostly due to a decreased spin-orbit coupling in Sb and the subsequent increased electronic delocalization compared to the Bi alloys, reducing the energy transfer to Mn2+ centers. This work lays out a roadmap to understand and achieve high photoluminescence efficiencies in layered double perovskites.
SI SbMn final