Ultrafast Study of Exciton Transfer in Sb(III)-Doped Two-Dimensional [NH(CH)NH]CdBr Perovskite.

Antimony-based metal halide hybrids have attracted enormous attention due to the stereoactive 5s electron pair that drives intense triplet broadband emission. However, energy/charge transfer has been rarely achieved for Sb-doped materials. Herein, Sb ions are homogeneously doped into 2D [NH(CH)NH]CdBr perovskite (Cd-PVK) using a wet-chemical method. Compared to the weak singlet exciton emission of Cd-PVK at 380 nm, 0.01% Sb-doped Cd-PVK exhibits intense triplet emission located at 640 nm with a near-unity quantum yield. Further increasing the doping concentration of Sb completely quenches singlet exciton emission of Cd-PVK, concurrently with enhanced Sb triplet emission. Delayed luminescence and femtosecond-transient absorption studies suggest that Sb emission originates from exciton transfer (ET) from Cd-PVK host to Sb dopant, while such ET cannot occur with Pb-doped Cd-PVK because of the mismatch of energy levels. In addition, density function theory calculations indicate that the introduced Sb likely replace the Cd ions along with the deprotonation of butanediammonium for charge balance, instead of generating Cd vacancies. This work provides a deeper understanding of the ET of Sb-doped Cd-PVK and suggests an effective strategy to achieve efficient triplet Sb emission beyond 0D Cl-based hybrids.