Device Preparation and Experimental Methods

Vjt denotes the drain voltage, Vq and Fx are gate and threshold voltage, respectively, (see colour plates p. LXXX) 

Without air-exposure the devices were transferred into a vacuum-chamber providing a pressure of less than 5 x 10 mbar for characterisation. The output and transfer characteristics of the transistors were measured using two independent source-meter units (Keithley 236). In order to measure inverter transfer curves an additional source-meter unit (Keithley 2400) was implemented. 

The charge-carrier mobilities // and the threshold voltages V-y were extracted from the slope of the transfer characteristics in the saturation region d g K using the standard relationship  

Here W is the channel width, L is the channel length, is the gate-oxide capacitance per unit area, Vq is the gate voltage, and additionally Fp is the drain voltage. Mobility /j and threshold voltage Vj were determined from the linear regression of the measured data plotted as vs.. The in- 

For photoelectron spectroscopy organic layers (neat films and mixtures) with a nominal thickness of 25 nm were deposited on 100 nm thick gold films which were thermally evaporated onto oxidised Si wafers. The electronic properties of the films were characterised using X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) by employing monochromated A1 Ka radiation (hv = 1486.7 eV) for measurement of the core levels as well as ultraviolet radiation [He I (hv = 21.2 eV) and He II (hv = 40.8 eV)] for an analysis of the occupied states near the Fermi level. For a measurement of the secondary electron cut-off to determine the sample work function exactly, an additional bias (-2 V and -5 V) was applied to the sample. 

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