Phenanthrenequinone, a Nonvolatile, Nonhalogenated Solid Additive, for Enhancing Thermal Stability in Organic Solar Cells

Various types of additives have been reported to enhance the performance of organic solar cells (OSCs). However, commonly used solvent additives often compromise device stability and contain harmful halogen elements. Although many studies have introduced high-boiling-point solvent additives and solid additives, these materials often contain toxic components or require a complex synthesis. In particular, a comprehensive understanding of their effects on device stability under various conditions is still lacking. In this study, we introduce 9,10-phenanthrenequinone (PQ), a commercially available, low-cost, nonvolatile, and nonhalogenated solid additive. The addition of PQ enhances the overall device stability by reducing energy disorder under ambient conditions and suppressing phase segregation, thereby improving the morphological stability under illumination and thermal stress. Notably, PQ-based unencapsulated devices retained over 93% of their initial power conversion efficiency after 100 h of thermal stress at 85 °C, with negligible burn-in degradation, representing one of the best thermal stability results reported for PM6:Y6 binary systems. This comprehensive stability study not only provides valuable guidance for the long-term reliability of bulk heterojunction OSCs but also highlights the potential of nonvolatile, nonhalogenated solid additives, such as PQ, which combines low cost, commercial availability, environmental friendliness, and improved efficiency and stability, for the future commercialization of OSCs.