A new medium-bandgap fused-[1]benzothieno[3,2-b][1]benzo-thiophene (BTBT) nonfullerene acceptor for organic solar cells with high open-circuit voltage

Abstract

A new nonfullerene small molecule acceptor, namely DBTIC, based on an octocyclic thieno[3,2-b]thienodi(indenothiophene) unit using [1]benzothieno[3,2-b][1]-benzothiophene as the core unit, was developed. Despite the medium-bandgap of DBTIC (1.71 eV), a power conversion efficiency of 8.64% can be delivered by the solar cells combining DBTIC and a wide-bandgap polymer donor J52. The high open-circuit voltage (Voc) of 0.94 V is also rare for J52 based devices owing to the high-lying lowest unoccupied molecular orbital level of DBTIC. Moreover, using J71 with lower highest occupied molecular orbital level as polymer donor, a higher Voc up to 1.05 V can be achieved.