Charge transport in three orthogonal directions in a single crystal of the conjugated polymer poly(3-hexylthiophene)

• Applicants: Privatdozent Dr. Leonid Govor; Professor Dr. Günter Reiter
• Subject Area: Experimental Condensed Matter Physics ; Polymer Materials
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 228230041

The goal of this proposal is the formation of single crystals of poly(3-hexylthiophene) (P3HT) of variable size and degree of order for the study of the anisotropic charge transport mechanisms in these crystals. A field effect transistor configuration is chosen, where a P3HT crystal (some 10 nm thick, ca. 1 µm wide, many µm long) bridges four gold electrodes located on a SiO2/Si substrate (gate electrode). In general, the measurements of the current-voltage characteristics I_d (V_d,V_g) at various temperatures in the range T=5-300 K will be made, where Id and Vd give the current and voltage between source and drain, Vg gate voltage. Such set of measurements allows us to determine: (a) mobility of charge carriers (µ ) as a function of an electric field and temperature; (b) the threshold voltage (for the onset of a current); (c) contact resistance at the interfaces of source-crystal and drain-crystal; (d) concentration of traps and their energy distribution; (e) activation energy in the dependence µ(1/T); (f) activation energy in Arrhenius plot g_d(1/T), where g_d=dI_d /dV_d gives the drain conductance; (g) general mechanisms of charge transport in a P3HT single crystal as a function of direction.

• DFG Programme: Research Grants