Unraveling the Physical Origin of Broadband Emission in Tin–Lead Mixed Perovskites

To determine the physical mechanism of broadband photoluminescence (PL) in halide perovskites, polycrystalline MAPb 1– x Sn x I 3 ( x = 0.25, 0.50, 0.75,1.00) was prepared. The study aimed to identify the two potential physical origins: self-trapped exciton (STE) recombination and defect-assisted recombination by luminescence characteristics. Analysis of data, including significant Stokes shifts, temperature dependence of photoluminescence, and sub-bandgap excitation power dependence, confirmed that low-energy photons effectively excite broadband luminescence. This study made clear that the defect-assisted radiative recombination is the primary factor governing broadband luminescence. The research established a physical picture of the broadband luminescence phenomenon, providing theoretical and experimental guidance for the controllable realization of high-performance broadband luminescent halide perovskite materials.