Herein, black cumin (Nigella sativa L.) defatted biowaste was chemically activated with zinc chloride to create AC. CdS, CdS@AC, and La-alloyed CdS@AC were subsequently created using the chemical precipitation process. IPCE technique was used for photovoltaic property detection of the created nanomaterials. The structural and morphological identifications of nanomaterials with the highest IPCE value among the created materials were measured by XRD, SEM, EDX, and XPS. According to the study's findings, 10% (for CdS@AC) was the ideal CdS concentration for achieving the highest solar cell efficiency or maximum IPCE (%). Additionally, the experimental results showed that 1% (for La-alloyed 10% CdS@AC) was the optimal La concentration with the maximum IPCE (%) value. Comparing pure CdS to 1% La-alloyed 10% CdS@AC, an excellent increase (from 4.70 to 30.03%) in IPCE (%) was seen. The findings of this work provide an alternative viewpoint on how to improve the solar cell performance for devices employing AC derived from biowaste-supported CdS semiconductor nanomaterials.