Role of Electron–Phonon Coupling in the Thermal Evolution of Bulk Rashba-Like Spin-Split Lead Halide Perovskites Exhibiting Dual-Band Photoluminescence

The optoelectronic properties of lead halide perovskites strongly depend on their underlying crystal symmetries and dynamics, sometimes exhibiting a dual photoluminescence (PL) emission via Rashba-like effects. Here we exploit spin- and temperature-dependent PL to study single-crystal APbBr₃ (A = Cs and methylammonium; CH₃NH₃) and evaluate the peak energy, intensity, and line width evolutions of their dual emission. Both perovskites exhibit temperature trends governed by two temperature regimesabove and below approximately 100 Kwhich impose different carrier scattering and radiative recombination dynamics. With increasing temperature, high-energy optical phonons activate near 100 K to drive energy splitting of the dual bands and induce line width broadening via electron–phonon coupling, with a stronger coupling constant inferred for carriers recombining by the spin-split indirect bands, compared to the direct ones. We find that the unusual thermal evolutions of all-inorganic and hybrid bulk lead bromide perovskites are comparable, suggesting A-site independence and the dominance of dynamic effects, and are best understood within a framework that accounts for Rashba-like effects.