Benzodithiophene-Based Broad Absorbing Random Copolymers Incorporating Weak and Strong Electron Accepting Imide and Lactam Functionalized Pyrrolo[3,4-c]pyrrole Derivatives for Polymer Solar Cells

• Published in: Macromolecular chemistry and physics 2015-05, Vol.216 (9), p.996-1007
• Main Authors: Tamilavan, Vellaiappillai, Roh, Kyung Hwan, Agneeswari, Rajalingam, Lee, Dal Yong, Cho, Shinuk, Jin, Youngeup, Park, Sung Heum, Hyun, Myung Ho
• Format: Article
• Language: English
• Subjects: 3-dione based polymers; 4-c]pyrrole-1; 4-dione based polymers; Absorption; Amides; Copolymers; Derivatives; Energy gaps (solid state); Hole mobility; imide functionalized polymers; lactam functionalized polymers; Photovoltaic cells; polymer solar cells; pyrrolo; pyrrolo[3,4‐c]pyrrole‐1,3‐dione based polymers; pyrrolo[3,4‐c]pyrrole‐1,4‐dione based polymers; Solar cells
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.201400614

Two benzodithiophene (BDT)‐based broad absorbing low band gap random copolymers, P1 and P2, incorporating electron accepting imide functionalized pyrrolo[3,4‐c]pyrrole‐1,3‐dione (TDPPDT) and lactam functionalized pyrrolo[3,4‐c]pyrrole‐1,4‐dione (DKPP) derivatives are prepared. The copolymerization of differently alkylated two TDPPDT derivatives with both of BDT and DKPP offers random copolymers P1 and P2. The absorption bands of polymers P1 and P2 cover the region from 300 to 900 nm and the estimated band gaps of P1 and P2 are 1.43 and 1.39 eV, respectively. The highest occupied molecular orbital energy levels of P1 and P2 are identical, at –5.25 eV. The organic field effect transistors made from P1 and P2 provide a hole mobility μ of 3.0 × 10−4 and 3.6 × 10−5 cm2 V−1 s−1, respectively. Polymer solar cells (PSCs) prepared from P1 and P2 afford a maximum power conversion efficiency of 1.64% and 2.14%, respectively. Two new broad absorbing random polymers are prepared. The incorporation of an electron accepting pyrrolo[3,4‐c]pyrrole‐1,4‐dione unit in the pyrrolo[3,4‐c]pyrrole‐1,3‐dione‐based, large‐band‐gap polymer main chain lowers the band gap notably, while maintaining the hole mobility. These random polymers are found to offer reasonable power conversion efficiencies when used in PSCs.