A facile synthetic approach based on thieno[3,4-c]pyrrole-4,6-dione to construct polymer donors for highly efficient organic solar cells

To realize the application of organic solar cells (OSCs), emphasis must be placed on reducing material cost, which is one of the golden triangle elements. One key strategy to address this issue is to optimize the synthetic method of the active layer materials. Herein, a convenient synthetic route of thieno[3,4-c]pyrrole-4,6-dione (TPD) acceptor unit derivatives was developed, which greatly minimizes the synthetic cost of the relevant polymer donors (P(D)s). Relying on the designed synthetic route, two TPD-based P(D)s, namely PTTB-H and PTTB-F, were synthesized. Both P(D)s without and with fluorine substitution possessed similar optical properties, but PTTB-F exhibited deeper molecular energy levels and stronger aggregation behavior in the solid state. The OSCs based on PTTB-F with weaker intermolecular forces in comparison with PTTB-H showed a decent PCE of 18.06% when blended with the small molecule acceptor L8-BO, which improves the open-circuit voltage and shapes a suitable phase separation morphology. Further studies showed that PTTB-F can match multiple acceptors and exhibit promising device performance. This study presents a low-cost approach to synthesizing electron-deficient TPD units for the construction of P-D materials with excellent universality and superior performance.