Challenges to the Stability of Active Layer Materials in Organic Solar Cells.

In the past 20 years, organic solar cells (OSCs) have made great progress in pursuing high power-conversion efficiencies, reaching the application threshold. Instead, device stability is becoming particularly important toward commercialization. There are many factors influencing the stability of OSCs, such as light, heat, humidity, oxygen, as well as device structure. Active layer materials, as the most critical functional layer in the devices, are greatly affected by these factors in terms of both efficiency and stability. Herein, it is desirable and urgent to summarize methods for obtaining active layer materials with long-term stability, mainly focusing on the chemical structure and blending morphology. Meanwhile, the corresponding degraded mechanism of OSCs is concluded and analyzed. In this outlook, challenges for developing high-performance and stable OSCs are discussed.