Fabrication and microstructure of $p$-type transparent conducting CuS thin film and its application in dye-sensitized solar cell

By reducing film thickness to a few nanometers, the narrow-band-gap CuS turns highly transparent. Surface modification by a self-assembled monolayer is the key factor to obtain a thin, dense, and continuous film. The film growth mechanism is identified as “layer-by-layer growth followed by islanding.” After annealing, a $p$-type conductivity of $\sim 2\times {10}^3\mathrm{S}{\mathrm{cm}}^{-1}$ is achieved at room temperature, and the thinnest conductive film has an average transparency of 92% between 400 and $800\mathrm{nm}$. Using $p$-type CuS films as front contact layers, a dye-sensitized solar cell was fabricated with a significant photoelectric response.