PerspectiveMaterials Science

Unraveling Charge Transport in Conjugated Polymers

See allHide authors and affiliations

Science  06 Sep 2013:
Vol. 341, Issue 6150, pp. 1072-1073
DOI: 10.1126/science.1242935

You are currently viewing the summary.

View Full Text

Summary

Polymer semiconductors have picked up the pace in the constant search for new and better electronic materials. High carrier mobility is an essential figure-of-merit for their applications as thin-film transistors (TFTs), solar cells, and light-emitting diodes. Polymers are disordered materials with partial crystallinity, and disorder introduces localized electronic states at the band edges—the so-called band tail—that trap electrons and reduce mobility. Reaching a mobility of 1 cm2 V−1 s−1 was the result of engineering polymers with increased crystallinity to reduce the effect of band tail states. Reported mobilities have recently surged to between about 5 and 10 cm2 V−1 s−1 (1), but the polymers are less ordered, according to some structural measurements. Two recent papers help resolve this puzzle. Zhang et al. (2) use a combination of structural probes to show that the high-mobility polymers gain longer-range structural order, if not high crystallinity, by having a more rigid backbone. Noriega et al. (3) provide a careful analysis of the role of disorder in charge transport for the specific case of polymers, and conclude that high crystallinity is not essential for high mobility.