Recent Investigations on the Use of Copper Complexes in Photovoltaic Application

Copper complexes have recently emerged as key materials for advancing dye-sensitized solar cells (DSSCs) toward more sustainable and high-performance photovoltaic technologies. This minireview summarizes the most significant achievements reported from 2024 onwards, highlighting the multifaceted role of copper in DSSCs as sensitizers, redox mediators, and functional components in innovative device architectures. Significant progress has been achieved in all these roles; however, the most remarkable advances concern copper-based redox mediators, where fine-tuning of ligand environments, additives, and electrolyte formulations has enabled excellent efficiencies, exceeding 10%, together with outstanding long-term stability. Developments in aqueous and quasi-solid-state systems further enhance the environmental compatibility and durability of these devices. In addition, novel concepts, including retro cells and copper-based "zombie" DSSCs, demonstrate the versatility of copper chemistry in simplifying device design and enabling new applications. Overall, these findings confirm copper complexes as highly promising earth-abundant alternatives to noble-metal-based systems although further work is still required to optimize light absorption, suppress charge recombination, and improve large-scale device stability.