In situ growth of CuInS(2) nanocrystals on nanoporous TiO(2) film for constructing inorganic/organic heterojunction solar cells

Inorganic/organic heterojunction solar cells (HSCs) have attracted increasing attention as a cost-effective alternative to conventional solar cells. This work presents an HSC by in situ growth of CuInS(2)(CIS) layer as the photoabsorption material on nanoporous TiO(2) film with the use of poly(3-hexylthiophene) (P3HT) as hole-transport material. The in situ growth of CIS nanocrystals has been realized by solvothermally treating nanoporous TiO(2) film in ethanol solution containing InCl(3) · 4H(2)O, CuSO(4) · 5H(2)O, and thioacetamide with a constant concentration ratio of 1:1:2. InCl(3) concentration plays a significant role in controlling the surface morphology of CIS layer. When InCl(3) concentration is 0.1 M, there is a layer of CIS flower-shaped superstructures on TiO(2) film, and CIS superstructures are in fact composed of ultrathin nanoplates as ‘petals’ with plenty of nanopores. In addition, the nanopores of TiO(2) film are filled by CIS nanocrystals, as confirmed using scanning electron microscopy image and by energy dispersive spectroscopy line scan analysis. Subsequently, HSC with a structure of FTO/TiO(2)/CIS/P3HT/PEDOT:PSS/Au has been fabricated, and it yields a power conversion efficiency of 1.4%. Further improvement of the efficiency can be expected by the optimization of the morphology and thickness of CIS layer and the device structure.