Electronic, optical and charge transfer properties of α,α′-bis(dithieno[3,2-b:2′,3′- d]thiophene) (BDT) and its heteroatom-substituted analogues

The ground state geometry of α,α′-bis(dithieno[3,2-b:2′,3′-d]thiophene) (BDT) and its heteroatom-substituted analogues have been optimized using B3LYP/6-31G∗∗ and PBE0/6-31G∗∗ level of theories. The absorption spectra have been computed in the presence and absence of solvent at PCM and CPCM models. The designed analogues where sulfur was substituted by NH (NHBDT), oxygen (OBDT) are blue shifted while BH substituted one (BHBDT) is red shifted. The vertical ionization potentials of NHBDT and OBDT are comparatively smaller than BDT revealing that injection barrier for hole would be small. The calculated vertical electronic affinity of BHBDT is 3.32 eV while its vertical ionization potential is 6.53 eV. Balanced hole and electron reorganization energies predicted that it would be good ambipolar material.