A straightforward capable strategy to adjust the solid-state morphology, opto-electronic and photovoltaic properties of conjugated co-polymers has been studied by inserting different percentages of N,N-dimethylthiophene-3-carboxamide (TDM) monomeric units. The TDM percentage was varied from 20 to 100%, resulting in widening of the energy band gap. Solar cells were fabricated using ITIC-4F as the electron acceptor to achieve a power conversion efficiency (PCE) of 7.8% for P4 (minimum TDM) and 0.85% for P1 (maximum TDM) in a thermal tempering process. A drastic drop in the PCE was noted with increasing percentage of TDM which agrees well with the optical, electronic, and morphological studies. Morphological analysis revealed high crystallinity for P4:ITIC-4F blend having minimum percentage of TDM units compared to its counterparts of higher TDM percentages. A sharp increase in π-π stacking can be seen as the percentage of TDM units decreases, with a d spacing of ̴ 3.6 Å. Detailed investigations regarding the charge carrier transport in relation to the π-π stacking of the polymeric film was well implemented in this work.