Enhanced Triplet Energy Transfer in Quantum Dot–Molecule Hybrids by Driving Bright State Redistribution

Optimizing triplet energy transfer (TET) performance between quantum dots (QDs) and molecules is crucial, because it enables efficient triplet sensitization with promising optoelectronic applications. Current strategies prioritize static parameters such as QD size or shell engineering but pay less attention to fine-structured bright-dark excitonic states inherent to QDs. Herein, we demonstrate a thermally driven bright-dark redistribution as the governing mechanism for TET enhancement in naphthalene-functionalized CdSe/ZnS QDs. Temperature-resolved spectroscopy resolves a photoluminescence splitting (∼18 meV) below 233 K due to reverse-TET-mediated dark exciton accumulation. Critically, thermally activated redistribution elevates the bright-state proportion from 33.9% to 49.1%, achieving a 4.2-fold increase in TET rate and enhancing efficiency from 26.9% to 73.3%. This work establishes exciton engineering as a strategic approach for TET optimization in QD-molecular hybrids and provides fundamental insights into advanced photonic and energy conversion technologies.