In this study, the performance of activated carbon (AC) produced from defatted black cumin (Nigella sativa L.) by chemical activation with zinc chloride (ZnCl2) activator in photovoltaic application is evaluated. It is of great importance to increase the photovoltaic efficiency of cadmium sulfide (CdS)-based solar cells, which are widely used in photovoltaic applications, with AC support. The main purpose of the study is to determine how the incident photon-to-current conversion efficiency (IPCE) of undoped and Mo-doped AC supported CdS semiconductor materials changes in the presence of AC support material and to interpret the observed effect in the light of literature. For these reasons, in the study, AC supported CdS (CdS/AC) (5%, 10%, and 15% by weight) and Mo-doped CdS/AC semiconductor materials with different molybdenum (Mo) concentrations (0.33%, 1%, 3%) are produced by chemical precipitation method. Produced CdS/AC and Mo-doped CdS/AC semiconductor materials are characterized by IPCE, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) measurements. Based on the result values, the optimum CdS concentration with the highest IPCE (%) value is determined as 10% (for CdS/AC). As a result of the experimental measurements, the optimum Mo concentration with the maximum IPCE (%) value is found as 1% (for Mo-doped CdS/AC). In particular, it is clear that an appreciable increase (from 4.70 to 39.00%) in IPCE (%) of 1% Mo-doped 10% CdS/AC semiconductor material is achieved when compared to pure CdS. Thus, the ability to increase the photovoltaic efficiency of CdS-based solar cells, which are widely used in photovoltaic applications, with AC support has been clearly demonstrated. This study presents a new strategy to increase the solar cell efficiency of semiconductor-based solar cell structures using biowaste-based AC supported CdS semiconductor materials.