Synthesis and characterization of alkoxyphenylthiophene substituted benzodithiophene-based 2D conjugated polymers for organic electronics applications

Abstract

In order to establish the correlation between intramolecular non-covalent interactions in the polymer backbone and the position/nature of alkoxy side chains in electron rich unit, two new series of low band gap polymers (P1–P4; P5–P8) were synthesized. We observed significant changes in photophysical properties upon changing the position and nature of the alkoxy side chain with respect to their intramolecular non-covalent interactions in the backbone, which are reflected in their field-effect transistors mobilities and photovoltaic properties. The Uv–Vis spectra of polymers containing a thieno[3,4-c]pyrrole-4,6-dione unit shows a vibronic shoulder, and the intensity of vibronic shoulder varies upon changing the position and nature of alkoxy side chain, in contrast, this type of absorption shoulder was not observed in polymer series containing a benzo[c][1,2,5]-thiadiazole moiety. In the thieno[3,4-c]pyrrole-4,6-dione series, a maximum power conversion efficiency of 4.19% with an open-circuit voltage of 0.91 V was noted. The power conversion efficiency of a benzo[c][1,2,5]-thiadiazole containing polymers was improved upon addition of 1,8-diiodooctane with maximum of 5.26% being recorded for polymer solar cells.