Correlation between Molecular Stereostructure, Film Microstructure, and Electronic Structure of Polyfluorene and Fluorene Based Alternating Copolymers F8BT and PFO-DBT

Identifying key parameters that can help control molecular ordering in the active layer of high-performance organic devices is an important topical issue. Finding a correlation between the spatial molecular structure of polymer backbones and the thin film's structural and optoelectronic properties is thus of utmost importance. In this paper, the influence of the backbone spatial structures of homopolymer PFO and copolymers F8BT and PFO-DBT with various stereoisomers varying by the up or down spatial orientation of individual chemical units in the comonomer on the film microstructure and electronic structure is studied. The computed energetics of the stereoisomers revealed at least two energetically favorable stereoisomers in both copolymers. These theoretical findings correlate with the thin film's crystallinity analyzed by the GIWAXS method, which showed ill packing in copolymers with stereoisomers. Thus, the molecular stereostructure was identified as a critical parameter that can help control molecular organization in active layers of organic photonic devices.