Pulsed laser deposition of CuInS₂ quantum dots on one-dimensional TiO₂ nanorod arrays and their photoelectrochemical characteristics

In the typical solution-based synthesis of colloidal quantum dots (QDs), it always resorts to some surface treatment, ligand exchange processing or post-synthesis processing, which might involve some toxic chemical regents injurious to the performance of QD sensitized solar cells. In this work, the CuInS₂ QDs are deposited on the surface of one-dimensional TiO₂ nanorod arrays by the pulsed laser deposition (PLD) technique. The CuInS₂ QDs are coated on TiO₂ nanorods without any ligand engineering, and the performance of the obtained CuInS₂ QD sensitized solar cells is optimized by adjusting the laser energy. An energy conversion efficiency of 3.95% is achieved under one sun illumination (AM 1.5, 100 mW cm^-2). The improved performance is attributed to enhanced absorption in the longer wavelength region, quick interfacial charge transfer and few chance of carrier recombination with holes for CuInS₂ QD-sensitized solar cells. Moreover, the photovoltaic device exhibits high stability in air without any specific encapsulation. Thus, the PLD technique could be further applied for the fabrication of QDs or other absorption materials.