Iron-coordinating π-conjugated semiconducting polymer: morphology and charge transport in organic field-effect transistors

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-06, Vol.8 (24), p.8213-8223
• Main Authors: St. Onge, P. Blake J, Chen, Tzu-Chien, Langlois, Adam, Younus, Aneeta, Jo Hai, I, Lin, Bi-Hsuan, Chiu, Yu-Cheng, Rondeau-Gagné, Simon
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Atomic force microscopy; Charge transport; Chelation; Conjugation; Coordination compounds; Field effect transistors; Iron; Ligands; Morphology; NMR; Nuclear magnetic resonance; Optical properties; Optoelectronics; Polymers; Semiconductor devices; Solid state; Spectrum analysis; Transistors; X ray photoelectron spectroscopy; X-ray fluorescence
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc01536a

A rational side-chain engineering was performed on a semicrystalline semiconducting conjugated polymer based on diketopyrrolopyrrole (DPP) to incorporate metal-chelating moieties without disruption of the π-conjugation. Specifically, a benzimidazole pyridine-based pincer ligand (MeBZIMPY), known to easily coordinate with M( ii ) metal centers, was inserted into the conjugated polymer and the effect of Fe( ii ) coordination on the optical properties was probed by absorption spectroscopy. Moreover, a careful analysis was performed on the metallopolymer in the solid state by grazing incidence X-ray diffraction and atomic force microscopy to evaluate the effect of coordination on the nanoscale morphology and chain packing. Coordination of Fe was directly confirmed by X-ray fluorescence spectroscopy and X-ray near edge absorption spectroscopy experiments. The resulting semiconducting metallopolymer was shown to possess a good solubility in common organic solvents after complexation and a smooth morphology at the nanoscale. The electronic properties of the new metallopolymer were evaluated through fabrication of organic field-effect transistors (OFETs). Interestingly, coordination of Fe( ii ) by the pincer ligand-containing DPP polymer was shown to enhance the charge mobility in organic field-effect transistors, going from 0.84 to 1.18 cm 2 V −1 s −1 upon coordination, which can be directly attributed to the influence of the metal complex on the solid-state morphology. The direct coordination of Fe( ii ) through pincer ligands is a promising strategy to enhance the charge transport and modulate the optoelectronic properties of π-conjugated polymers without the use of π-conjugation breaking units and/or multi-step synthesis. A new approach to improve charge transport and solid-state morphology in a semiconducting polymer was developed through metal coordination without disruption of the π-conjugation.