Solution-Processed CuSCN Films With Low Toxic and Environmentally Friendly Solvent for Efficient All-Inorganic CuInS₂ Solar Cells

Indium copper sulfide (CuInS $_{{2}}\text {)}$ has attracted considerable attention as an efficient and stable photon-absorbing material for inorganic heterojunction solar cells. Hole transport layer (HTL), serving as a hole extracting material, plays an integral role in determining device performance of solar cells. Here, the high-quality CuSCN film has been prepared successfully by using green mixed solution (dimethyl sulfoxide and dipropyl sulfide) and employed firstly to fabricate efficient CuInS2 planar heterojunction (PHJ) solar cells. The morphology, absorption properties, crystallinity and crystal orientation of CuSCN film are investigated by scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis) and X-ray diffraction (XRD) techniques. Results show the CuSCN film layer ( ${T}_{c} = 100~^{\text {o}}$ C) suggests good crystallinity and superior transmittance. The champion CuInS2 PHJ solar cell with inorganic CuSCN HTM achieves an inspiring power conversion efficiency ( $\eta \text {)}$ of 5.0% with the highest fill factor (FF) of 65.66% in the similar photovoltaic devices.