Commodity Polymer Serving As Interfacial Layer For Improved Air And Mechanical Stability

In recent years,thanks to the rapid development of donor and acceptor materials,the maximal power conversion efficiency(PCE)of organic solar cells(OSCs)has exceeded 18%.However,in order to realize the commercialization,not only the PCE value should be further enhanced,but also the long-term stability should be significantly improved.The donor and acceptor tend to experience physical and chemical degradation upon exposing to water,oxygen and illumination.Therefore,in order to improve the stability of solar cells,the other solution relies on interfacial layer.The commonly used interfacial layers are the metal oxides or conjugated polyelectrolytes,which are initially unstable.The article introduces the commercial polymers using for interfacial layer,to improve the air and mechanical stability.First,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.On the other hand,in the solar cells with normal structure,the commonly used PEDOT:PSS hole transporting layer exhibits of disadvantage of acidity and hygroscopicity.In addition,the alcohol soluble polyelectrolytes electron transporting layer tend to be degraded upon illumination.The article propose a method to insert an insulating polystyrene-r-polymethyl methacrylate(PS-r-PMMA)between PEDOT:PSS and active layer.Additionally,the polyvinylidene fluoride(PVDF)was served as electron transporting layer to realize the inner encapsulation.After illumination for 360 h in air environment,the device could still retain 80%of its original PCE value.In contrast,the device with the traditional normal structure exhibits of a serious depression in PCE value remaining 40%of its original value.