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 (VOC ) 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 VOC 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 VOC . This work attests that DTBT-based p-type polymers are ideal for the application in high-voltage OSCs.
Keywords: dithienobenzothiadiazole; high-voltage; organic solar cells; voltage loss; wide-bandgap nonfullerene acceptor.
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