Additive-mediated morphology regulation: a critical strategy toward efficient and stable organic solar cells

Abstract

Solution-processed organic solar cells (OSCs) represent a promising candidate for next-generation photovoltaic technology. Improving efficiency is vital for advancing OSCs toward commercialization. The active layer morphology, including ideal phase separation, molecular packing and orientation, and domain size, significantly influences exciton dissociation and charge transport, ultimately determining device performance. To achieve optimal morphology, numerous photoactive materials have been developed through trial and error. Meanwhile, various morphology control techniques have been promoted to maximize the potential of photoactive materials. One particularly effective and straightforward method is the incorporation of additives during film processing. Recent reports highlight the importance of additives in optimizing active layer morphology and pursuing high-performance OSCs. Nevertheless, it is important to note that the current mainstream additives contain halogen atoms, which pose risks to human health and the environment, and can negatively impact device stability and performance. Herein, developing ecofriendly and highly effective additives is crucial for the commercialization of OSCs. In this review, we categorize representative additives based on the presence of halogen atoms and explain their working mechanisms. Furthermore, by analyzing their structures and mechanisms, we provide reasonable design guidance for additives. Finally, the challenges and future perspectives on the advancement of additives are briefly outlined.