Study on The Network Formation Mechanism of The Photoactive Domains in Organic Photovoltaics

Organic photovoltaics (OPVs) have emerged as a promising technology for clean energy generation, characterized by their cost-effectiveness, solution processability, and high transparency. In recent years, there has been a spike in power conversion efficiency from the continuous development of nonfullerene small molecule acceptors. However, despite recent performance improvements, a comprehensive mechanism analysis on the network formation of the donor and acceptor domains needs more investigation. In this study, the morphology transition mechanism of the bulk-heterojunction network was studied to identify the photoactive domain formation process. In-situ UV-vis absorption analysis showed that the donor polymers established a network framework, acting as a structural body in the system, with small molecules subsequently penetrating this structure. It was also confirmed by mapping the solidified network, visually showing clear donor and acceptor domains. Crucially, the drying environment during the deposition of donor and acceptor solutions plays a pivotal role in determining the network structure. Leveraging this insight, a novel additive material that effectively controls the drying speed of acceptor molecules was employed, resulting in improved performance of OPV devices. Lastly, the system was also applied to fabricate semitransparent OPV with over 3.5 light utilization efficiency values.