Bandgap Engineering of Halide Perovskites to Modulate Singlet and Triplet Energy Transfer Pathways

Semiconductor nanocrystals are capable of transferring singlet or triplet energy to an adsorbed dye molecule. The bandgap energy of the semiconductor donor, excited state energetics of a dye acceptor dictate the efficiency of energy transfer processes. For example, rhodamine dyes bound to CsPbBr 3 nanocrystals undergo singlet energy transfer while those bound to CsPbI 3 nanocrystals participate in triplet energy transfer. To map out the triplet energy transfer deactivation pathway of excited perovskite nanocrystals we have varied the bandgap of donor perovskite nanocrystal through compositional control of Br/I ratio. The bandgap tuning through mixed halide composition has allowed us to establish the dependence of singlet and triplet energy transfer on the energetics of perovskite nanocrystals. Furthermore, incorporation of Mn 2+ in the perovskite lattice increases triplet characteristics and significantly improves the triplet energy transfer pathway. The transient absorption and emission studies which provide new insights into energy transfer processes of halide perovskite- dye hybrid assemblies will be discussed.