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Voltage [V]43.532.521.510.500 600PositionFig 9. Potential along a cross-section line in the scaled structure.In another simulation run the device was scaled to the targeted60 cm keeping the same layer structure. In this casethe potential drop was about 90% (see Fig. 9), which definitelyshows the need for a shunting grid.B Measurement resultsCurrent–voltage characteristics were measured at 10 differenttemperature values between 5°C and 50°C. Themeasured I–V curves are presented in Fig. 10.Based on these measurement results we already startedcreating temperature dependent lumped SPICE-like modelaimed at circuit level simulation.VII. FUTURE WORKWe need to complete the infrared thermal measurement ofthe demo device. Here there are a couple of problemsforeseen, since with the IR camera we have to look at the24-26 September 2008, Rome, Italydevice from the light emitting side. If the usual blackpainting is applied at the top of the transparent substrate, wetrap the generated light in the black paint – this way realizingan extra heating sheet on the OLED device. The effect ofthis heating hovewer can be considered if the radiometricflux (ie. the P opt emitted optical power) of the device ismeasured. Knowing this, we can account for the energytrapping in the black paint (which is aimed at providinguniform emissivity of the measured surface for IRtermography). This the steady-state thermal simulation of theOLED device can be validated. We also hope, that thermaltransient testing (as suggest before) can be used to validatedynamic simulation results. Both IR and thermal transientmeasurements are believed to allow us a comprehensivethermal simulation model validation.Measuring the total luminous and radiometric flux of theOLED in an integrating sphere while the ambienttemperature of the OLED is controlled by attaching it to acoldplate is important since this allows a proper interpretationIR measurement results, as outlined in the previousparagraph.These measurement results together with the I–Vcharacteristics make the derivation of multi-domain spicelikecompact models possible.VII. CONCLUSIONSOur investigations proved that it is inevitable to accompanythe transparent organic anode layer by a shunting grid inan OLED device of 60x60cm 2 . The simulation of the smallerstructure gave a hint on the density of the required grid:around 1 cm (depending on the cross-sectional area of a singlegrid line it might change).Parameter is the temperature [°C]10050 45 40 35 30 25 20 15 10 5908070Current [mA]60504030201002.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0Voltage [V]Fig 10. Measured current–voltage characteristics.©EDA Publishing/THERMINIC 2008 239ISBN: 978-2-35500-008-9