N-Fluorinated Benzene Effects on Thiophene-Quinoxaline Random Polymers for Well-Ordered film Morphology and Molecular Orientations

Abstract

Introducing halogens as strong electron-withdrawing groups onto the conjugated main backbone is a well-known synthetic strategy to render the designed semiconducting organic materials suitable for optoelectronic devices. In our report, a series of novel thiophene-quinoxaline (TQ) based conjugated random copolymers containing phenyl units substituted with the different number of fluoride atoms are synthesized for use in organic photovoltaic devices. The influence of the number of fluoride substitutions on a phenylene moiety as one of building blocks leads to considerable changes in the lowest unoccupied molecular orbital (LUMO) particularly and structure-property relationship of twisted adjacent units as demonstrated through density functional theory (DFT) analysis. Following nature properties with computational studies, packing orientations of each polymer are investigated thoroughly in grazing incidence wide-angle X-ray scattering (GIWAXS) to probe the intercalation of acceptors into the novel donor polymers. With comparison to the only TQ polymer via a range of techniques, the role of multiple-substituted fluoride atoms on conjugated materials is suggested intuitively as a promising block in polymer based solar cells with relatively efficient power conversion efficiency (PCE) of 6.3 %.