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.