High figure-of-merit p-type transparent conducting Cu–Zn–S thin films with Zn doped CuS structure were successfully deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature. Films were deposited with an optimal Cu:Zn:S ratio of 75:25:50 in the precursor solution. The thickness of the films was controlled by varying the number of deposition cycles. The composition, structure, morphology, electrical, electronic and optical properties of the as deposited films were studied in detail. All the films exhibited relatively high conductivity and transparency resulting in high figure-of-merit values. Overall, the hole concentration and conductivity are in the range of degenerately doped semiconductors. The Cu–Zn–S film deposited with 40 nm thickness has an electrical conductivity of more than 1000 S/cm and average optical transparency greater than 81% in the visible region. These values are higher than most of the other reported p-type transparent conducting materials, especially for room temperature deposition. Conventional bulk heterojunction organic solar cells were fabricated with structure ITO/Cu–Zn–S/P3HT:PC71BM/ZnO/Al, where Cu–Zn–S is the hole transport layer. The best configuration resulted in an efficiency of 1.87% suggests the suitability of Cu–Zn–S thin films as a hole transport layer in organic solar cells.