CuInS2 Quantum Dot-Sensitized Solar Cells Fabricated via a Linker-Assisted Adsorption Approach

Colloidal chalcopyrite CuInS2 (CIS) quantum dots (aDs) were synthesized using copper(I) iodine (Cul) and indium(III) acetate (InAc3) as metal cationic precursors, and dodecanethiol (DDT) as the sulfur source and solvent. The microstructure and optical properties of the prepared CIS QDs were characterized by X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and UV-Vis absorption spectroscopy. The results showed that the CIS consisted of chalcopyrite phase and exhibited Cu-Au ordering. With prolonged reaction time, the grain sizes of the QDs became larger and the absorption edges of the CIS QDs showed a red-shift owing to the size-induced quantum confinement effect. For the first time, DDT-capped CIS QDs with narrow size distribution were connected to the inner surface of mesoporous TiO2 films via a thioglycolic acid (TGA)-assisted adsorption approach, which was simple and easy to carry out. The adsorption behaviors of both TGA and the CIS QDs on the TiO2 films were detected by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results indicated that TGA was adsorbed onto the surface of TiO2 via COOH groups while the -SH group was exposed outside, and replaced DDT at the surface of the CIS QDs, leading to the attachment between TiO2 and CIS. It was revealed that the CIS QDs of similar to 3.6 nm in size exhibited the best light absorption capacity and photovoltaic performance. An over-coating of CdS significantly improved the performance of the QDSSCs owing to decreased electron recombination, and a power conversion efficiency of similar to 2.83% was obtained.