Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Joint Session: Organic Semiconductors IV: Excitations and Charges
HL 54.7: Vortrag
Mittwoch, 16. März 2011, 16:00–16:15, ZEU 222
Surface Doping of Conjugated-polymer/Insulating-polymer Composite Film for Field-effect-transistor — •Guanghao Lu1,2, Patrick Pingel2, Ingo Salzmann1, Norbert Koch1, and Dieter Neher2 — 1Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany — 2Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany
In organic field-effect-transistors, optimized devices are usually achieved at inert environment together with passivated dielectric surface, in order to prevent the possible doping by oxygen or polar groups at dielectric surface. However, in this work, we find that the field-effect properties of poly(3-hexylthiophene)/polystyrene (P3HT/PS) composite can be greatly improved upon surface doping. Upon exposure to air and using oxidablely active dielectric surface, we doped the top surface and bottom surface of P3HT/PS film for top-contact and bottom-contact devices, respectively. The field-effect mobility of these films with only 2-5 wt% P3HT can be enhanced by more than 3 orders, reaching 0.05-0.2 cm2V-1s-1. This phenomenon is strongly contrary to the case of pure P3HT film. We proposed that, for pure P3HT, doping inevitably induces negatively charged sites or charge-transfer complexes, which act as new traps or undesired low energy sites. However, for conjugated-polymer incorporated within insulating-polymer matrix, the interaction between hole and surrounding negative sites is weaker because of the spatial occupation of a-PS among P3HT domains, which largely optimizes the positive aspect of doping and meanwhile restrained its negative role.