“…Such increased degree of crystallinity is known to induce a larger interchainmolecular interaction leading to more delocalized conjugated π electrons, consequently producing a low band gap and enhanced optical π-π * transition resulting in a more effective photon absorption (Motaung et al, 2009) as depicted in Figure 2. Pristine PBDB-T used as a donor shows Raman modes at 1,427, 1,452, 1,487, and 1,540 cm −1 , which are assigned to the C α =C β symmetric stretching mode, antisymmetric stretch mode of C α =C β , skeletal stretching mode of C β -C β and antisymmetric C α -S-C α ring skeleton that depict distortion of the in-plane vibrations of the thiophene ring of PBDB-T (Gao et al, 2018). Other less intense peaks are at 1,075, 1,231, and 1,598 cm −1 and may be assigned to the stretching mode of C β -C alkyl , C-H bending mode, and antisymmetric stretch mode of C α =C β , respectively (Kabongo et al, 2016).…”