Tuning The Optoelectronic Properties Of Scaffolds By Using Variable Central Core Unit And Their Photovoltaic Applications

Central core modification is convenient strategy to adjust the optoelectronic properties that allows significant utilization of small fullerene free donor materials in photovoltaic technology. Herein, four push-pull conjugated molecules in acceptor-donor-acceptor (A-D-A) configuration are investigated through quantum chemical simulations. A comprehensive DFT study of reference R and designed donor materials (D1 -D4) in which core is linked with thiophene spaced end-cap acceptors is conducted via selected functional MPW1PW91 and basis set (6-31G). Various critical parameters required to upgrade the efficiency of small molecule donors are electronic energy gaps, optical properties and exciton dynamics that are characterized by frontier molecular orbital diagram, absorption graph, transition density matrix (TDM), density of states (DOS), open-circuit voltage (Voc), and reorganization energy of charge carriers. Red shift occurs in all studied fluorine bearing scaffolds which absorb strongly in visible range 634-690 nm as compared to previously reported non-fluorinated molecule (598 nm). Amongst all donor molecules, D3, elucidates desirable photovoltaic characteristics i.e., highest absorption peak (690 nm), appropriate energy gap (2.17 eV) and considered to be the ideal aspirant in photovoltaics. Furthermore, reduction in reorganization energy and increment in Voc values illustrate that all molecules possess faster charge carrier mobilities than reference. This conceptual study clarified that we could amend the optoelectronic parameters by replacing core with variable electron rich components. Hence, these novel molecules containing fluorine should be recommended for construction of high-performance organic solar cells in future.