Strategy to Manipulate Molecular Orientation and Charge Mobility in D–A Type Conjugated Polymer through Rational Fluorination for Improvements of Photovoltaic Performances

Abstract

Improving the photoelectric conversion efficiency of organic solar cells (OSCs) is an essential issue for large scale commercial applications. Introducing the fluorine (F) atoms onto the electron-accepting unit and/or electron-donating unit on donor (D)–acceptor (A) type conjugated polymer is an effective strategy to enhance the overall solar cell performance. Here, the optimum sites for fluorination in favor of boosting the optical and photovoltaic properties of polymers are fully investigated by density functional theory (DFT) calculation and molecular dynamics (MD) simulation. Especially, the interchain charge mobility is calculated by means of Marcus theory, to investigate the charge transport process quantitatively. The results of theoretical modeling indicate that, except for the enhanced absorption spectra and deep lying HOMO level, more importantly, a higher hole mobility could be achieved when F is introduced onto the 3,6 position (outer site) of quaterthiophene for two reasons: (1) more effectiv...