Degradation Mechanisms in Highly Efficient Organic Solar Cells Based on Non-Fullerene Acceptors

During recent years, organic solar cells composed of different donor-acceptor-type polymers and non-fullerene acceptors (NFA) have approached and even exceeded the 20% hurdle. However, still questions remain regarding their long-term stability, i.e. the degradation processes involved.<br/>Here, we present a comprehensive study on ca. 10 different NFAs and try to derive structure/property relations regarding their chemical stability / degradation mechanism, respectively. Experiments include the 1) analysis of the chemical stability of the NFAs themselves by mass spectrometry, 2) electrochemical stability tests of the radical anions (“electrons”), 3) solar cell devices based on PCE-12 and the NFAs, respectively, as prepared ones as well as aged by accelerated life-time testing, and 4) chemical analysis of the degradation products.