Taking as a device model ITO|TPD|Alq 3 |Al (where TPD is N,N'-bis(3-methylphenyl)-N,N'-diphenyl-1,1'biphenyl-4,4'-diamine and Alq 3 is tris(quinolin-8-olato)aluminium) it is shown that control and improvement of carrier injection may be achieved using self-assembled monolayers (SAMs) to manipulate the Schottky energy barrier at the ITO±TPD interface. By using polar adsorbate molecules with the dipole oriented outward from the surface an arti®cial dipolar layer is formed and the work function is increased, and vice versa. With this method the threshold voltage for light emission (turn-on) can be reduced by 4 V and the maximum luminance increased by a factor of 3.5, giving an overall performance superior to that using the more stable Ag/Mg counter electrode. The SAMs effect is con®rmed using a Scanning Kelvin Probe (SKP) to pro®le the relative work function of half-coated ITO samples. Increases in work function in excess of 0.3 eV are observed, in line with predictions using the calculated molecular dipoles of the SAM molecules.

In this work we report the effect of post deposition film treatment on the N0 2 sensing properties of CuPc thin films for room temperature operation. The gas sensitive response of the electrical conductivity to doping with N0 2 , doping with oxygen (in air) and cooling to 77K in liquid nitrogen are reported. The pretreatment with N0 2 is shown to improve the gas sensing properties by providing both an increase in the magnitude of the conductivity change for a given N0 2 concentration and a significant improvement in the recovery time. Data is analysed using an Elovich model, which suggests that the cooled devices have the best fit to this model; the data for the N0 2 doped devices suggest a Langmuir behaviour. For all devices, a simple time derivative of the change in current provides a measure of concentration for real time gas sensing applications.

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