Research Progress of Thermal Failure Mechanism and Ternary Blending to Improve Thermal Stability of Organic Solar Cells

As an emerging high-efficiency solar cell, organic solar cells (OSCs) have been developed rapidly in recent years. The power conversion efficiency (PCE) of OSCs has reached more than 19%, which is the dawn of commercial application. However, the stability of OSCs is not yet satisfied, especially high processing and operation temperature may be applied to the cells, which requires a high thermal stability of the cells. The ternary strategy, where a third component is introduced into the photoactive layer of donor-acceptor based binary OSCs, was found to be able to simultaneously improve device performance and stability by regulating the intermolecular interactions, showing a great potential for application. In this review, we firstly summarized the mechanisms involved in the thermal decay process of OSCs, including thermally induced morphology changes of the photoactive layer, interfacial aging/chemical reactions, and interdiffusion behavior between the layers. Following this, the research progress of the ternary strategies in improving thermal stability are highlighted, and the mechanism for the stabilization effect is reviewed. By the end, the perspective of the ternary strategies in OSCs is given, pointing out that the selection of the proper third component and the understanding on the mechanism of the stabilization effect are the key issues and challenges.