Strategies for Resilient Organic Photovoltaics

Organic solar cells (OSCs) offer a distinct set of advantages among next-generation photovoltaics, i.e. their flexibility, lightweight design, low-cost manufacturing, and semi-transparency. Substantial efforts have been invested in boosting device efficiency, and this potential is now underpinned by impressive laboratory-scale efficiencies approaching 20%. As efficiency gradually approaches commercialization requirements, the stability of OSCs becomes increasingly paramount in academic research. Numerous factors can influence device stability, including delamination of the photo-active layer or interface triggered by oxygen and water, light-induced chemical alterations in materials, and thermally induced morphological changes. Therefore, it is imperative to comprehend the stability bottlenecks of high-efficiency systems at this stage towards real-world applications.<br/>In this talk, I will elaborate on the stability of various non-fullerene acceptors (NFAs) and different polymer donors for OSC. We established a connection between the molecular structure of Y-series NFAs, specifically the endgroup and side-chain, and their photostability, ultimately affecting the device's lifetime. We also explored the significance of various polymer donors in determining device longevity and highlighted the side-chain-induced degradation pathway in polymer donors. We further provided theoretical tools for understanding the photostability of polymer donors. Photochemical degradation in both Y-NFAs and polymer donors, under illumination, leads to a significant increase in trap-assisted recombination, resulting in decreased device performance under outdoor conditions. We systematically compared the photostability, thermal stability, and outdoor stability of devices fabricated with state-of-the-art materials, aiming to gain a comprehensive understanding of how the photoactive layers influence long-term performance in the hot and sunny climate of Saudi Arabia. Furthermore, I will propose new strategies to simultaneously improve the photostability, thermal stability, and outdoor stability of devices for resilient organic photovoltaics. Overall, our findings offer valuable insights for the design and synthesis of photoactive materials, with the goal of achieving both high efficiency and long-term stability in OSCs for real-world applications.