The wet chemical method was used to prepare ZnS:Cu (3%) nanoparticles. The capping agent (mercaptoethanol) was handled during the synthesis process. To investigate the photovoltaic properties of ZnS:Cu (3%) nanoparticles synthesized via the wet chemical method, the incident photon to electron conversion efficiency (IPCE) measurement was performed. The IPCE (%) value at 400 nm was found as 5.12. This result shows that successfully synthesized ZnS:Cu (3%) nanoparticles can be used as promising sensitizers in solar cell technology. The energy band gap value of ZnS:Cu (3%) nanoparticles with cubic structure was determined as approximately 3.92 eV. In this study, it is emphasized that it is possible to develop both photovoltaic properties and optical properties of ZnS nanoparticles by using additive metal.