Dithienobenzothiadiazole (DTBT)‐Based Polymers Enable Organic Solar Cells with Ultrahigh VOC of ≈1.3 V

Abstract Dithieno[3’,2’:3,4;2",3":5,6]benzo[1,2‐c][1,2,5]thiadiazole (DTBT) is a newly emerging building block to construct effective photovoltaic polymers. Organic solar cells (OSCs) based on DTBT‐based polymers have realized power conversion efficiency (PCEs) over 18%, despite their relatively low open‐circuit voltage ( V OC ) of 0.8–0.95 V. To extend the application of DTBT‐based polymers in high‐voltage OSCs, herein, D18‐Cl and PE55 are used to combine with a wide‐bandgap non‐fullerene acceptor (NFA), BTA3, and achieve ultrahigh V OC of 1.30 and 1.28 V, respectively. Compared with D18‐Cl based on tricyclic benzodithiophene (BDT) segment, PE55 containing the pentacyclic dithienobenzodithiophene (DTBDT) unit possesses better hole mobility, higher charge‐transfer efficiency, and more desirable phase separation. Hence, PE55:BTA3 blend exhibits a higher efficiency of 9.36% than that of D18‐Cl: BTA3 combination (6.30%), which is one of the highest values for OSCs at ≈1.3 V V OC . This work attests that DTBT‐based p‐type polymers are ideal for the application in high‐voltage OSCs.