Solution-processed fabrication of copper indium sulfide (CuInS 2 ) as optical absorber for superstrate CuInS 2 /CdS/TiO 2 solid-state solar cells

Copper indium sulfide (CuInS 2 , CIS) photo-absorber layer fabricated by solution-processed strategies have received significant attention in development of thin-film solar cell. The superstrate Au/CIS/CdS/TiO 2 thin-film solar cell was constructed on a single FTO substrate. The CdS deposited TiO 2 nanostructures were prepared by chemical bath deposition to form a uniform CdS buffer layer. Furthermore, CIS solutions containing copper, indium and sulfur precursors were spin-coated to yield p–n junctions between CIS and CdS. The CIS based solar cell performance was investigated by optimizing devices to achieve an efficient light harvesting and transport of photo-generated charge carriers. The performances of solar cells were optimized to be 1.2% of PCE. It is considered that the presence of both dense-TiO 2 layer which acts as a blocking layer and porous TiO 2 which tightly holds CdS and CIS, improve the solar cell performance due to a highly efficient charge separation. These present results suggest that CIS superstrate solar cells prepared by facile nano-structuring approaches provide stable and efficient low-cost photovoltaic devices.