A Thiazole-Based Polymer Donor for Efficient Organic Solar Cells

The development of new materials plays a critical role in improving the efficiency of organic solar cells（OSCs）.At present,the relatively high-lying highest occupied molecular orbital（HOMO） level of the high-efficiency polymer donor is regarded as one of the main reasons for the low open-circuit voltage(VOC).In this work,we introduced the strong electron-withdrawing thiazole unit into the construction of a polymer donor.We designed and prepared an alternating donor-acceptor material,namely PSZ,by copolymerizing 4-methyl thiazole with an electron-donating benzodithiophene unit and studied its application in high-efficiency OSCs.The optical and electrical properties of the new material were characterized by UV-Vis absorption spectroscopy and electrochemical cyclic voltammetry.Results show that PSZ is a typical wide-bandgap material with a high optical bandgap of 2.0 eV and a deep HOMO level of-5.70 eV.When a non-fullerene BTP-eC9 was selected as the acceptor material,VOC reached 0.88 V in the resulting device,and the corresponding power conversion efficiency（PCE） was8.15%.In addition,when PSZ was added as the third component to the binary photoactive combination with PBDB-TF as the donor and BTP-eC9 as the acceptor,VOC of the cell device could be increased,thereby obtaining a high PCE of 17.4%.These results indicated that introducing thiazole units into polymer donors can remarkably reduce the HOMO levels and improve VOC and PCE in OSCs.