Dithienobenzochalcogenodiazole-based electron donor–acceptor polymers for organic electronics

• D-A copolymers containing thiophene-fused benzochalcogenodiazole are synthesized.
• Optoelectronic properties are tunable by changing the chalcogen atoms.
• The chemical structures and phase separation determine device performances.

Appositely functionalized dithienobenzo-thiadiazole and dithienobenzo-oxadiazole-monomers were prepared and used in the synthesis of conjugated electron donor-acceptor (D-A) polymers. Detailed systematic investigations were carried out to study the effects of chalcogen atoms and three donor units on the optical and electrochemical properties as well as photovoltaic and field-effect transistor performance of the D-A polymers. All polymers displayed good thermal properties. Polymers containing benzooxadiazole moiety showed deeper LUMO levels as compared to their benzothiadiazole-containing analogues, whereas those derived from weak donor unit exhibited deeper HOMO levels than those with stronger donors. Photovoltaic power conversion efficiency of over 2% and hole field-effect mobility of 2.6 × 10−2 cm2V−1s−1 and on/off ratio of over 105 were obtained. These results demonstrate that dithienobenzo-chalcogenodiazole structures are potentially useful electron acceptor building blocks for the construction of D-A polymers for organic electronics applications.

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