Enhanced Photocurrent and Electron Transfer via Shell Thickness Control in Blue-Emitting Graded Alloy Core/Shell “Giant” Quantum Dot–Organic Acceptor Hybrid Structures: Implications for Photocatalysis

This study investigates the influence of shell thickness on charge separation dynamics in blue-emitting graded alloy core/shell “giant” quantum dots (g-QDs) interfaced with an organic electron acceptor, benzoquinone (BQ). Photoinduced electron transfer (PET) experiments were conducted to evaluate how shell permeability and energetic alignment affect charge transfer. Steady-state and time-resolved fluorescence spectroscopy reveal that thinner-shell g-QDs exhibit more pronounced emission quenching and faster exciton decay upon addition of BQ, indicating efficient nonradiative charge transfer. PET efficiency, calculated from the ratio of the electron transfer rate to the total decay rate, was found to be the highest in g-QDs with the thinnest shells. Complementary photoelectrochemical measurements, including photocurrent (I–T) responses, confirmed enhanced charge extraction and suppressed radiative recombination in 7.8 nm diameter g-QDs. These findings highlight the critical role of shell thickness in optimizing exciton dissociation and the charge transfer efficiency. This work provides key insights for designing blue-emitting g-QDs for advanced photocatalysis and light-harvesting applications.