Influence of an Amide-Functionalized Monomeric Unit on the Morphology and Electronic Properties of Non-Fullerene Polymer Solar Cells

Abstract

A straightforward competent strategy to attune 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. Fabrication of solar cells was performed with ITIC-4F as an electron acceptor to accomplish power conversion efficiencies (PCEs) of 7.8% for P4 (minimum TDM) and 0.85% for P1 (maximum TDM) under 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 pi-pi stacking is seen with reduced percentage of TDM units, leading to d spacing of 3.6 angstrom. Detailed investigations regarding the charge carrier transport in relation to the pi-pi stacking of the polymeric film are well implemented in this work.