Eco-Friendly Non-Volatile Solid Additives for High-Efficiency Sustainable Organic Photovoltaic Cells

Abstract

As organic photovoltaics (OPVs) have become increasingly commercially viable in recent years, with power conversion efficiency (PCE) exceeding 20%, the importance of environmental sustainability has also grown significantly. While most eco-friendly OPV developments have focused on replacing solvents in the photoactive layer with benign alternatives, reliance on harmful additives for morphology modulation remains a major obstacle to achieving fully sustainable OPVs. This study presents the first example of a fully eco-friendly OPV, achieved by incorporating novel, non-volatile, eco-friendly solid additives, specifically, 4,4’-dihydroxybiphenyl (DBP), 4,4’-dimethylbiphenyl (DMBP), and 2,2’-dihydroxy-4-methoxybenzophenone (DM), in combination with the eco-friendly solvent o-xylene. Among them, DBP demonstrates the highest performance and long-term stability due to its superior miscibility and higher boiling point, achieving a PCE of 17.78%. Enhanced crystallinity and optimal phase separation morphology within the photoactive layer by DBP contribute to improvements in charge transfer, mobility, and device stability. This development marks a significant step toward the commercialization of sustainable OPVs, meeting the dual objectives of high efficiency and environmental compatibility.