Improving the performance of quantum dot sensitized solar cells by employing Zn doped CuInS2 quantum dots

In this paper, the Zn-CuInS2 and CuInS2 quantum dots (QDs) were synthesized by heat injection method and were explored as photosensitizers for quantum dot sensitized solar cells (QDSCs). The X-ray diffraction (XRD) analyses indicate that the synthesized Zn-CuInS2 QDs with chalcopyrite structures have a slight shift towards large angle direction with the increase of doping concentrations. The UV–vis absorption and photoluminescence (PL) emission spectra show that Zn doping expands the range of optical absorption and enhances the luminescence intensity. The Zn-CuInS2 QDs with the particle size of around 6.5 nm and homogeneous size distribution are observed by transmission electron microscope (TEM). The current density–voltage curves show that Zn-CuInS2 QDSCs exhibit a conversion efficiency of 2.90%, 17.17 mA/cm2 of short circuit current density (Jsc), 0.42 V of open circuit voltage (Voc), 30.9% of fill factor (FF) at 100 mW/cm2 AM 1.5G illumination. The ZnS coating reduces the recombination of electron–hole pairs and improves the electron injection efficiency. The short-circuit current and power conversion efficiency (PCE) are improved with the increase of pH value and Mercaptopropionic acid (MPA) concentrations. The response range of photocurrent and IPCE of photoanode are improved by Zn doping and ZnS coating strategy.