Indacenodithieno[3,2- b ]thiophene-Based Wide Bandgap D-π-A Copolymer for Nonfullerene Organic Solar Cells.

Herein, a wide-bandgap (2.02 eV) donor-π-acceptor (D-π-A) polymer PIDTT-DTffBTA, composed of a rigid indacenodithieno[3,2- b ]thiophene (IDTT) and fluorinated benzo[ d ][1,2,3]triazole (ffBTA) units as D and A units, respectively, is synthesized. In comparison with its analogue benzodithiophene- alt -benzotriazole copolymer J52 with classic benzodithiophene (BDT) as the D unit, PIDTT-DTffBTA demonstrates a lower-lying HOMO energy level and higher carrier mobilities when paired with a nonfullerene acceptor (NFA) Y6 based on a ladder-type dithienothiophen[3.2- b ]-pyrrolobenzothiadiazole central unit. Thus, PIDTT-DTffBTA:Y6 based organic solar cells (OSCs) exhibit an improved power conversion efficiency (PCE) of 11.05% than that of J52:Y6 (7.15%), which is also the highest value for IDTT-based photovoltaic polymers. This result proves that the IDTT unit is also a promising building block to construct not only NFAs but also p-type photovoltaic polymers.