Design and Synthesis of Dibenzothiadiazolopyrrolothiophene (DBTPT)-Based Acceptors for Efficient Organic Photovoltaic Cells

The central core in non-fullerene acceptors (NFAs) plays a crucial role in determining the efficiency of organic photovoltaic (OPV) cells. To further advance the development of OPV cells, it is crucial to synthesize novel central cores for constructing high-performance NFAs. Here, dibenzothiadiazolopyrrolothiophene (DBTPT) is introduced, a ladder-type [1,2,5]thiadiazolo[3,4-e]indole-fused pentacyclic thiophene unit, into photovoltaic materials. By employing the DBTPT unit as the rigid molecular backbone and modifying the side chain of the thiophene pi-bridge, two new acceptor-pi-acceptor'-donor-acceptor'-pi-acceptor (A-pi-A'DA'-pi-A)-type acceptors (T6 and T9) are synthesized. The effects of lateral alkyl and alkoxy side chains on the optoelectronic properties, charge transport, and molecular packing order are systematically investigated. When blended with polymer donor Poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5'7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T), the blend film based on T9 with alkoxy side chains shows favorable molecular stacking and phase separation, resulting in excellent charge transfer performance. Benefiting low energetic disorder, PBDB-T:T9-based cell achieves an efficiency of 12.6% with a markedly low energy loss of 0.568 eV. The preliminary results demonstrate that the DBTPT unit has great potential for the construction of novel NFAs for high-performance OPV cells. In this study, two A-pi-A'DA'-pi-A-type NFAs are synthesized, namely T6 and T9, for the first time. Both T6- and T9-based cells exhibit efficiencies exceeding 10%. These initial findings underscore the significant potential of the DBTPT unit in the development of novel NFAs, aimed at enhancing the performance of OPV cells. image