Copper(I) thiocyanate (CuSCN) is a wide bandgap and solution-processable p-type semiconductor with tremendous potential for large-area optoelectronic applications. In this work, chlorine-doped CuSCN (Cl2–CuSCN) was utilized to form a hole transport layer (HTL) for different organic solar cells (OSCs) and inverted perovskite solar cells (PSCs). Chlorine doping into CuSCN thin films is found to improve the device performance of different OSCs, to a level comparable to that of PEDOT:PSS-based OSCs. Notably, the inverted PSCs with Cl2–CuSCN showed a better performance than those with pristine CuSCN or PEDOT:PSS-based inverted PSC devices. Moreover, Cl2–CuSCN-based OSCs and PSCs also reveal significantly better stability than pristine CuSCN and PEDOT:PSS-based devices. Our results show how Cl2–CuSCN thin films act as a universally applicable HTL for emerging solar cell technologies, improving both device performance and stability.