New biphenylvinylanthracene-based polymers for organic electronics applications: effect of the acceptor group on optoelectronic properties

In this study, the molecular design of new semiconducting biphenylvinylvinylanthracene-type polymers with (Poly-BPAn) and without CN (Poly-BPAn-CN) groups in the main chain has been investigated. The two polymers (Poly-BPAn and Poly-BPAn-CN) were synthesized with high yields using Wittig and Knoevenagel polycondensation; respectively. Structural and thermal analyses (NMR, FTIR, TGA, DSC) confirmed the molecular structure and thermal stability up to 275 °C. Similar absorption profiles were revealed in optical analyses, indicating that steric effects are more significant than the electron-withdrawing influence of the cyano group. However, fluorescence efficiency and electron affinity were both affected by the CN group incorporation. The optimized macromolecular structure of both polymers was estimated using DFT, and there was a significant change in planarity based on the incorporated withdrawing group. Single-layer devices of the (ITO/Polymer/Al) configuration have been elaborated and showed relatively low turn-on voltages. Also, the electrical characterization showed a significantly remarkable improvement in mobility following the incorporation of the CN group into the conjugated system of Poly-BPAn-CN. The theoretical insertion of monolayer of optimized single walled carbon nanotubes (SWNTs) (5.5) permitting to reduce the barrier injection (ΔE_e) from the (Ca, Mg) cathode to the synthesized active layer Poly-BPAn and Poly-BPAn-CN, which improve the efficiency of the designed OLEDs.