Regio-regular alternating diketopyrrolopyrrole-based D <sub/>1</sub> –A–D <sub/>2</sub> –A terpolymers for the enhanced performance of polymer solar cells

摘要： We designed and synthesized regio-regular alternating diketopyrrolopyrrole (DPP)-based D1–A–D2–A terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) using a primary donor (D1) [3,30-di?uoro-2,20-bithiophene (F2T2)] and a secondary donor (D2) [2,20-bithiophene (T2), (E)-1,2-di(thiophen-2-yl)ethene (TVT), or dithieno[3,2-b:20,30-d]thiophene (DTT)]. A PDPP2DT-F2T2 D–A polymer was synthesized as well to compare optical, electronic, and photovoltaic properties. The absorption peaks of the terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) were longer (lmax ? 801–810 nm) than the peak of the PDPP2DT-F2T2 polymer (lmax ? 799 nm), which is associated with the high-lying HOMO levels of the terpolymers ((cid:2)5.08 to (cid:2)5.13 eV) compared with the level of the PDPP2DT-F2T2 polymer ((cid:2)5.38 eV). The photovoltaic properties of these DPP-based polymers were investigated under simulated AM 1.5G sunlight (100 mW cm(cid:2)2) with a conventional structure (ITO/PEDOT:PSS/polymer:PC71BM/Al). The open-circuit voltages (Voc) of photovoltaic devices containing the terpolymers were slightly lower (0.68–0.70 V) than the Voc of the device containing the PDPP2DT-F2T2 polymer (0.79 V). The short-circuit current (Jsc) of the PDPPF2T2DPP-DTT device was signi?cantly improved (14.14 mA cm(cid:2)2) compared with that of the PDPP2DT-F2T2 device (8.29 mA cm(cid:2)2). As a result, the power conversion e?ciency (PCE) of the PDPPF2T2DPP-DTT device (6.35%) was increased by 33% compared with that of the simple D–A-type PDPP2DT-F2T2 device (4.78%). The highest Jsc and PCE values (the PDPPF2T2DPP-DTT device) were attributed to an optimal nanoscopically mixed morphology and strong interchain packing with a high face-on orientation in the blend ?lm state. The study demonstrated that our strategy of using multiple donors in a regio-regular alternating fashion could ?ne-tune the optical, electronic, and morphological properties of D–A-type polymers, enhancing the performance of polymer solar cells.