Polyolefin Elastomer as the Anode Interfacial Layer for Improved Mechanical and Air Stabilities in Nonfullerene Solar Cells

Despite the breakthroughs in power conversion efficiency (PCE) values of organic solar cells (OSCs), the other important issue concerns stability, which is urgently needed to be resolved for potential commercialization. A commercial and chemically stable polyolefin elastomer (POE) was incorporated into high-performance PBDB-T:ITIC, PM6:IT-4F, and PM6:Y6 nonfullerene systems to serve as the anode interfacial layer, affording remarkably improved mechanical and air stabilities when compared with those of the most studied MoO3 interfacial layer. The POE was found to selectively transport holes rather than electrons due to the upshifted surface contact potential of the active layer and the better ohmic contact between the active layer and the electrode. The POE serving as an encapsulating layer is supposed to suppress the penetration of water and oxygen in addition to the diffusion of Ag atoms into the active layer. After storing in an air environment with a humidity of approximately 70% for 150 days, the PCE of the device based on PM6:IT-4F with the POE anode interfacial layer decreased from 11.88 to 9.60%, retaining 80.8% of its original PCE value. The device using MoO3 as the anode interfacial layer showed a PCE value that was sharply reduced from 12.31 to 2.98% after storing for only 30 days. The POE could be potentially useful for flexible and large-scale device fabrication, accelerating the commercialization of OSCs.