Bandgap and Molecular‐Energy‐Level Control of Conjugated‐Polymer Photovoltaic Materials Based on 6,12‐Dihydro‐diindeno[1,2‐b;10,20‐e]pyrazine

Six conjugated polymers based on the indenopyrazine ( IPY) unit are designed and synthesized by copolymerization with different electron‐deficient and electron‐rich building blocks. All of the polymers show good solubility, excellent film‐forming ability, and low‐lying highest occupied molecular orbit (HOMO) energy levels. The effects of the different copolymerized units on the optical, electrochemical, and photovoltaic properties are investigated. Results indicate that their bandgaps and molecular energy levels are readily tuned by copolymerizing with electron‐deficient and electron‐rich units. Polymer solar‐cell devices are fabricated utilizing the polymers as electron donors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) as an electron acceptor. The best power conversion efficiency of the cell based on PIPY‐DTBTA , one of the IPY‐ based polymers, reaches 0.77%, with a relatively high V_oc up to 0.78 V.