Abstract
Integrating carbon nanomaterials into solar energy technologies has emerged as a promising strategy to improve efficiency, scalability, and sustainability. Although graphene has excellent carrier mobility, electrical conductivity, and optical transparency, graphene derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO) suffer from significant structural defects and disruption of the sp(2)-hybridized carbon lattice caused by oxidative processing, severely limiting their electronic and optoelectronic performances. To address these limitations, minimally oxidized graphene (MOG), which includes non-oxidized graphene flakes (NOGFs) and low-oxidized graphene quantum dots (GQDs), has been developed via a nondestructive approach based on ion or molecular intercalation followed by liquid-phase exfoliation. These materials retain the integrity of a π-conjugated network and offer tunable functionalities and solution processability. NOGFs exhibit high conductivity, broadband light absorption, and thermal stability, making them ideal materials for use in solar cell electrodes, photothermal absorbers, and photocatalytic scaffolds. GQDs with tunable bandgaps and abundant functional groups serve as interfacial modifiers in solar cells and as active sites for photocatalysis. This review summarizes recent advances in MOG, focusing on structure-property-performance relationships and applications in solar energy conversion. A comparative evaluation with conventional GO/rGO-based systems is presented along with future directions toward developing high-efficiency graphene-enabled solar technologies.