Resolving Energy Transfer Dynamics at the Quantum Dot Gels-Perylene Diimide Hybrid Interface.

Semiconductor-molecular hybrids provide a platform for controlling excited-state transfer in photocatalysis and optoelectronics. While quantum dots (QDs) are promising semiconductors, they are often capped with surface ligands that limit accessibility and hinder coupling with molecular species. QD gels are a porous three-dimensional network of QDs that can address the limitations of QDs, making them especially advantageous for semiconductor-molecular hybrid systems; however, excited-state transfer dynamics remain largely unexplored. Here, we report energy transfer dynamics from a CdS QD gel to a vibronically fine perylene diimide (PDI) molecule, as revealed by transient absorption spectroscopy, with a characteristic time of ∼115 ps and an efficiency of ∼86%. Density functional theory calculations reveal that interfacial level alignment is strongly governed by quantum confinement, yielding a type-I heterojunction that is consistent with the experimentally observed energy transfer. These results highlight the potential of QD gels as a tunable framework for integrating molecular acceptors with quantum-confined materials.