Efficiency Enhancement of Solid-State CuInS2 Quantum Dot-Sensitized Solar Cells by Improving the Charge Recombination

Abstract

Copper indium sulfide quantum dots (CuInS2 QDs) were incorporated into a nanocrystalline TiO2 film by using spin coating-assisted successive ionic layer adsorption and reaction process to fabricate CuInS2 QD-sensitized TiO2 photoelectrodes for the solid-state quantum dot-sensitized solar cell (QDSSC) applications. The result shows that the photovoltaic performance of solar cell is extremely dependent on the number of cycles, which has an appreciable impact on the coverage ratio of CuInS2 on the surface of TiO2 and the density of surface defect states. In the following high-temperature annealing process, it is found that annealing TiO2/CuInS2 photoelectrode at a suitable temperature would be beneficial for decreasing the charge recombination and accelerating the charge transport. After annealing at 400 °C, a significantly enhanced photovoltaic properties of solid-state CuInS2 QDSSCs are obtained, achieving the power conversion efficiency (PCE) of 3.13%, along with an open-circuit voltage (VOC) of 0.68 V, a short-circuit photocurrent density (JSC) of 11.33 mA cm−2, and a fill factor (FF) of 0.41. The enhancement in the performance of solar cells is mainly ascribed to the suppression of charge recombination and the promotion of the electron transfer after annealing.