Size-Dependent Electron Injection and Photoelectronic Properties of CuInS2 Quantum Dot Sensitized Solar Cells

Size-dependent electron injection processes in CuInS2 (CIS) quantum dot sensitized solar cells (QDSSCs) were studied. CuInS2 quantum dots (QDs) with various diameters were synthesized and sensitized on TiO2 films. The energy levels of the CuInS2 QDs were measured by cyclic voltammetry. The rates and efficiencies of electron transfer from CuInS2 QDs to TiO2 films were determined by time-resolved photoluminescence spectroscopy. It was found that the rate of electron injection increased with a decrease in QD size while the efficiency of electron injection decreased. Furthermore, the power conversion efficiency, the short-circuit photocurrent, and the fill factor (FF) of the QDSSCs increased with an increase in QD size. The enhanced performance of the QDSSCs was attributed to the increase in electron injection efficiency. These results indicate that the performance of the QDSSCs could be optimized by varying the size of the QDs.