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

The Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.
Nature Materials (Impact Factor: 36.5). 06/2008; 7(5):376-80. DOI: 10.1038/nmat2165
Source: PubMed


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 -electron system to -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 (3–610-
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 J cm-
2) for 10 Hz, 12 ns, 390 nm excitation) and slope efficiencies (up to 11%

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    • "The most straight-forward way to eliminate concentration quenching is blending molecules with polymer host material. Unfortunately, diluting the material significantly reduces charge carrier mobility [14], and moreover adversely affects organic laser efficiency [8]. Nonetheless, this method is advantageous for determining the relation between ASE threshold and the molecular concentration in the low-loss waveguiding films. "
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