The Impact of Molecular p-Doping on Charge Transport in High-Mobility Small-Molecule/Polymer Blend Organic Transistors

Abstract
Molecular doping is a powerful tool with the potential to resolve many of the issues currently preventing organic thin-film transistor (OTFT) commercialization. However, the addition of dopant molecules into organic semiconductors often disrupts the host lattice, introducing defects and harming electrical transport. New dopant-based systems that overcome practical utilization issues, while still reaping the electrical performance benefits, would therefore be extremely valuable. Here, the impact of p-doping on the charge transport in blends consisting of the small-molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), the polymer indacenodithiophene-benzothiadiazole (C16IDT-BT), and the molecular dopant C60F48 is investigated. Electrical field-effect measurements indicate that p-doping not only enhances the average saturation mobility from 1.4 to 7.8 cm2 V−1 s−1 over 50 devices (maximum values from around 4 to 13 cm2 V−1 s−1), but also improves bias–stress stability, contact resistance, threshold voltage, and the overall device-to-device performance variation. Importantly, materials characterization using X-ray diffraction, X-ray photoemission spectroscopy, and ultraviolet photoemission spectroscopy, combined with charge transport modeling, reveal that effective doping is achieved without perturbing the microstructure of the polycrystalline semiconductor film. This work highlights the remarkable potential of ternary organic blends as a simple platform for OTFTs to achieve all the benefits of doping, with none of the drawbacks.

Citation
Paterson AF, Lin Y-H, Mottram AD, Fei Z, Niazi MR, et al. (2017) The Impact of Molecular p-Doping on Charge Transport in High-Mobility Small-Molecule/Polymer Blend Organic Transistors. Advanced Electronic Materials: 1700464. Available: http://dx.doi.org/10.1002/aelm.201700464.

Acknowledgements
T.D.A. and A.F.P acknowledge financial support from Cambridge Display Technology (Company No. 2672530). O.S. acknowledges the support of the Center for Absorption in Science of the Ministry of Immigrant Absorption under the framework of the KAMEA Program.

Publisher
Wiley

Journal
Advanced Electronic Materials

DOI
10.1002/aelm.201700464

Additional Links
http://onlinelibrary.wiley.com/doi/10.1002/aelm.201700464/full

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