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Simultaneous optimization of charge-carrier mobility and optical gain in semiconducting polymer films

Abstract

The combination of efficient light emission and high charge-carrier mobility has thus far proved elusive for polymer semiconductors, with high mobility typically achieved by cofacial π-electron system to π-electron system interactions that quench exciton luminescence1,2. We report a new strategy, comprising the introduction of a limited number of more effective hopping sites between otherwise relatively isolated, and thus highly luminescent, polyfluorene chains. Our approach results in polymer films with large mobility (μ≈3–6×10−2 cm2 V−1 s−1) and simultaneously excellent light-emission characteristics. These materials are expected to be of interest for light-emitting transistors3, light-emitting diode sources for optical communications4 and may offer renewed hope for electrically pumped laser action2,5,6. In the last context, optically pumped distributed feedback lasers comprising one-dimensional etched silica grating structures coated with polymer have state-of-the-art excitation thresholds (as low as 30 W cm−2 (0.1 nJ per pulse or 0.3 μJ cm−2) for 10 Hz, 12 ns, 390 nm excitation) and slope efficiencies (up to 11%).

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Figure 1: Polymer chemical structures and glassy film optical properties.
Figure 2: Time-of-flight photocurrent transients and field-dependent hole mobility data.
Figure 3: Performance of Y80F8:20F5 one-dimensional DFB laser.

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Acknowledgements

We thank T. Ohnishi and T. Yamada and the Sumitomo Chemical Co. for providing the polymers used in this study and for funding a PhD studentship for B.K.Y. We also thank the EPSRC (Ultrafast Photonics Collaboration Interdisciplinary Research Collaboration (GR/R55078) and Advanced Fellowship to P.N.S. (EP/C539494)) and the Commission of the European Community (FP6-IST-026365 POLYCOM) for financial support.

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Correspondence to Donal D. C. Bradley.

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Yap, B., Xia, R., Campoy-Quiles, M. et al. Simultaneous optimization of charge-carrier mobility and optical gain in semiconducting polymer films. Nature Mater 7, 376–380 (2008). https://doi.org/10.1038/nmat2165

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