Regio-regular alternating diketopyrrolopyrrole-based D1–A–D2–A terpolymers for the enhanced performance of polymer solar cells. Issue 72 (18th December 2019)

• Record Type: Journal Article
• Authors: Lee, Myeongjae; Kim, Taehyo; Nguyen, Hoai Van T.; Cho, Hye Won; Lee, Kyung-Koo; Choi, Jong-Ho; Kim, BongSoo; Kim, Jin Young
• Is Part Of: RSC advances. Volume 9:Issue 72(2019)
• Page Start: 42096
• Page End: 42109
• Publication Date: 2019-12-18
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9ra08858j
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : We designed and synthesized regio-regular alternating diketopyrrolopyrrole (DPP)-based D1 –A–D2 –A terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT ) for use in polymer solar cells. Abstract : 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, 3′-difluoro-2, 2′-bithiophene (F2T2)] and a secondary donor (D2 ) [2, 2′-bithiophene (T2), ( E )-1, 2-di(thiophen-2-yl)ethene (TVT), or dithieno[3, 2- b :2′, 3′- 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 ( λ max = 801–810 nm) than the peak of the PDPP2DT-F2T2 polymer ( λ max = 799 nm), which is associated with the high-lying HOMO levels of the terpolymers (−5.08 to −5.13 eV) compared with the level of the PDPP2DT-F2T2 polymer (−5.38 eV). The photovoltaic properties of these DPP-based polymers were investigated under simulated AM 1.5G sunlight (100 mW cm −2 ) with a conventional structure (ITO/PEDOT:PSS/polymer:PC71 BM/Al). The open-circuit voltages ( V oc ) of photovoltaic devices containing the terpolymers were slightly lower (0.68–0.70 V) than the V oc of the device containing the PDPP2DT-F2T2 polymer (0.79 V). The short-circuit current ( J sc ) of the PDPPF2T2DPP-DTT device was significantly improved (14.14 mA cm −2 ) compared with that of the PDPP2DT-F2T2 device (8.29 mA cm −2 ). As a result, the power conversion efficiency (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 J sc 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 film state. The study demonstrated that our strategy of using multiple donors in a regio-regular alternating fashion could fine-tune the optical, electronic, and morphological properties of D–A-type polymers, enhancing the performance of polymer solar cells.