Effect of extended alkyl auxiliary groups on optical and electronic properties of Benzo[2,1-b:3,4-b′:5,6-c″]trithiophene derivatives at bulk level: A first-principles study

Thiophene based π-conjugated compound, Benzo[2,1-b:3,4-b′:5,6-c″] Tri-Thiophene (BTT) has been acknowledged as a potential and state-of-the-art organic semiconductor materials (OSMs) for optoelectronic applications due to easy fabrication, mechanical flexible and environment friendly cheaper applications. In this study, some optoelectronic properties of π-conjugated BTT alkyl substituted derivatives BTT-C6 and BTT-C12 have been studied by density functional theory (DFT) at (GGA/PBE) level. Current study identifies the BTT-C6 as a direct band gap semiconductor having a band gap of 2.365 eV. Whereas, the band gap of BTT-C12 has been increased by 0.071 eV when compared to BTT-C6, because of the impact from p-orbitals of the crystals structures. The decline in the energy and density of states (DOS) for the systems under present study confirmed that band gap can be modified by varying the length of alkyl chains to an anticipated value for optoelectronic application by derivatives modeling. Furthermore, DOS, electronic band structure and optical properties (dielectric constant, extinction coefficient, refractive indices, reflectivity and conductivity) at solid state bulk level have been computed. After analyzing different optoelectronic properties at solid state level revealed that BTT derivatives would be efficient materials to be used in multifunctional organic semiconductor device applications.