New Benzodithiophene- and Benzooxadiazole/Benzothiadiazole-Based Donor-Acceptor π-Conjugated Polymers for Organic Photovoltaics

A new set of push-pull type 2D-conjugated polymers (P1-P4) were designed and synthesized where A1, A2 (oxygen analogues) and A3, A4 (sulfur analogues) are electron deficient units used as co-monomers. On introduction of new repeating units into the polymer backbone, significant changes were observed in optoelectronic properties. Furthermore, the heteroatom exchange in new repeating units has also brought notable changes in photophysical properties, in particular P1 and P2 (oxygen analogues) showed bathochromic shift in UV-vis absorption spectra and deeper HOMO energy levels than P3, P4 (sulfur analogues). Interestingly P1, P3 absorption spectra shows a vibronic shoulder (659, 652 nm) peak in lower energy region, and this might originated from non-covalent interactions between the electron rich and electron deficient units. In addition, the systematic investigation of these polymers with additive and solvent treatment, yielded in enhanced power conversion efficiency of 4.29% for P3-based devices in bulk heterojunction organic solar cells. (C) 2016 Wiley Periodicals, Inc.