Efficient side-chain engineering of thieno-imidazole salt-based molecule to boost the optoelectronic attributes of organic solar cells: A DFT approach

Abstract

This study focused on modeling and density functional theory (DFT) analysis of reference (AI1) and designed structures (AI11-AI15), based on the thieno-imidazole core, in order to create profitable candidates for solar cells. All the optoelectronic properties of the molecular geometries were computed using DFT and time dependent-DFT approaches. The influence of terminal acceptors on the bandgaps, absorption, hole and electron mobilities, charge transfer capabilities, fill factor, dipole moment, etc. Of the recently designed structures (AI11-AI15), as well as reference (AI1), were evaluated. Optoelectronics and chemical parameters of newly architecture geometries were shown to be superior to the cited molecule. The FMOs and DOS graphs also demonstrated that the linked acceptors remarkably improved the dispersion of charge density in the geometries under study, particularly in AI11 and AI14. Calculated values of binding energy and chemical potential confirmed the thermal stability of the molecules. All the derived geometries surpassed the AI1 (Reference) molecule in terms of maximum absorbance ranging from 492 to 532 nm (in chlorobenzene solvent) and a narrower bandgap ranging from 1.76 to 1.99eV. AI15 had the lowest exciton dissociation energy of 0.22eV as well as lowest electrons and hole dissociation energies, while AI11 and AI14 showed highest VOC, fill factor, power conversion efficiency (PCE), IP and EA (owing to presence of strong electron pulling cyano (CN) moieties at their acceptor portions and extended conjugation) than all the examined molecules, implying that they could be used to build elite solar cells with enhanced photovoltaic attributes.

Keywords: Materials; Organic solar cells; Photovoltaic attributes; Terminal modification; Theoretical approach; Thieno-imidazole salt.