Multilayer Graphene Oxide/Cadmium Selenide Quantum-Dot-Coated Titanium Dioxide Heterojunction Solar Cell

We demonstrate a heterojunction solar cell employing multilayer graphene oxide (ML-GO) as the hole-conducting layer and cadmium selenide (CdSe) quantum-dot-coated titanium dioxide (TiO₂) as the photoactive material. Multilayer graphene, synthesized by a chemical-vapor-deposition technique, is treated with low-power (25-W) oxygen plasma (~100 sccm) to convert into ML-GO, as confirmed by Raman spectroscopy. The ML-GO exhibits an optical bandgap of 3.6 eV extracted from UV-visible absorption spectroscopy. The heterojunction solar cell is implemented with a stacked heterostructure of ITO/TiO₂/CdSe/ML-GO/Pt, yielding a short-circuit current density of 11.2 mA/cm², an open-circuit voltage of 652 mV, and a photoconversion efficiency of 4.1% under a standard AM 1.5 illumination condition.