Facile fabrication of carbon quantum dot-based CdS and Co-doped CdS nanocomposites as effective sensitizers for solar cell applications: a hydrothermal synthesis approach

The development of efficient and sustainable materials for solar energy conversion remains a key challenge in renewable energy research. Cadmium sulfide (CdS) nanoparticles are widely used as sensitizers in solar cells due to their favourable optoelectronic properties. However, their efficiency is often limited by charge recombination and poor electron transport. To overcome these limitations, this study explores the incorporation of carbon quantum dots (CQDs) and cobalt (Co) doping into CdS nanocomposites (NCs) to enhance their photovoltaic performance. CQDs, synthesized from mulberry molasses via a hydrothermal method, were incorporated into CdS to improve charge separation, while Co doping was employed to reduce recombination losses. The structural and electronic properties of the synthesized CdS/CQD and Co-doped CdS/CQD NCs were thoroughly characterized using Fourier transform infrared spectroscopy (FT–IR), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet–visible (UV–Vis) spectroscopy. The photovoltaic performance was evaluated by current–density-voltage (J–V) measurements, revealing that the Co-doped CdS/CQD NCs exhibited superior efficiency (2.21%) compared to CdS/CQD (2.17%). The observed improvement is attributed to enhanced electron injection and reduced recombination due to Co doping. These results highlight the potential of Co-doped CdS/CQD NCs as effective sensitizers in solar cells, offering a promising strategy for the advancement of sustainable photovoltaic technologies.