Energy Transfer and Self-Trapping Exciton Luminescence in Sb³⁺-Doped Two-Dimensional Layered Dion-Jacobson Phase Cadmium-Based Perovskites

Two-dimensional (2D) Dion-Jacobson (D-J) phase metal halides have been extensively studied for their excellent optical properties. However, the charge/energy transfer between the host and dopant of Sb3+-doped 2D structures has rarely been reported. Here, Sb3+-doped (PPDA)CdCl4 (PPDA = p-phenylenediamine) 2D layered D-J phase perovskites with strong electron-phonon coupling and fast energy transfer (E-T) from the host to the dopant lead to strong yellow emission with a photoluminescence quantum yield of 75.4%. Femtosecond-transient absorption (fs-TA) spectra reveal that Sb3+-doped 2D layered perovskites exhibit positive phonon-coupled electronic states with a biexcitonic nature, as well as the E-T mechanism from the bound excitons of the host material to the Sb3+ dopant for the CB and VB state mixing between Sb and Cd. Further, we exhibited Sb3+-doped (PPDA)CdCl4 in the application of solid-state lighting due to its superb optical properties and impressive stability. This work provides new insights for investigating the optical properties of 2D luminescent materials, especially the exciton-dopant exchange interactions in Sb3+-doped 2D D-J phase perovskites and also promotes the widespread use of this material in solid-state lighting.