Efficient charge separation and enhanced photocurrent of CdTe quantum dots-Au nanoclusters composite with type-II band alignment

Abstract

Quantum dots (QDs)-based composites are promising candidates for optoelectronic and photonic devices. Understanding the photo-induced carrier dynamics is fundamental and crucial for improving the photoelectric conversion efficiency of nanocomposites. In this work, we have constructed nanocomposite hybridizing CdTe QDs with Au nanoclusters (Au NCs) and investigated the ultrafast carrier dynamics and enhanced photoelectric properties. The concurrent photoluminescence quenching and lifetime decreasing of CdTe QDs and Au NCs suggest a type-II band alignment, facilitating the carrier dynamics in the CdTe QDs-Au NCs' nanocomposite. The transient absorption measurements demonstrate an ultrafast and efficient electron transfer from CdTe QDs to Au NCs, effectively promoting the charge separation and inhibiting the exciton recombination. We found that the quantum efficiency of hot electron transfer can reach ∼50% with a rate constant of 1.01 × 1013 s−1 for the CdTe QDs-Au NCs' nanocomposite. As a result, the photocurrent performance of the CdTe QDs-Au NC device has been dramatically enhanced due to the efficient separation of photogenerated carriers, compared to that of individual CdTe QDs and Au NCs. These findings are significant for developing the light-harvesting and photoelectric devices based on semiconductor QDs and metal NCs.