Exploring the Effect of Band Alignment and Surface States on Photoinduced Electron Transfer from CuInS₂/CdS Core/Shell Quantum Dots to TiO₂ Electrodes

Photoinduced electron transfer (ET) processes from CuInS₂/CdS core/shell quantum dots (QDs) with different core sizes and shell thicknesses to TiO₂electrodes were investigated by time-resolved photoluminescence (PL) spectroscopy. The ET rates and efficiencies from CuInS₂/CdS QDs to TiO₂ were superior to those of CuInS₂/ZnS QDs. An enhanced ET efficiency was surprisingly observed for 2.0 nm CuInS₂ core QDs after growth of the CdS shell. On the basis of the experimental and theoretical analysis, the improved performances of CuInS₂/CdS QDs were attributed to the passivation of nonradiative traps by overcoating shell and enhanced delocalization of electron wave function from core to CdS shell due to lower conduction band offset. These results indicated that the electron distribution regulated by the band alignment between core and shell of QDs and the passivation of surface defect states could improve ET performance between donor and acceptor.

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