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Published online by Cambridge University Press: 24 February 2016
We demonstrate Ag-free transparent OLED (TOLED) fabricated by organic vapor phasedeposition (OVPD) using thin Au contacts. Three types of TOLED devices have beenstudied. The first one has been deposited on ITO substrates to compare thin Agand Au films as top cathodes. A 6-fold increase in operational lifetime(LT50, 4 mA/cm2) from 27 h to 172 h can be observedwhen replacing Ag by Au while maintaining similar electro-opticalcharacteristics. Furthermore, a second type of TOLED on thin Au films, replacingITO and suppressing laterally guided modes [1], has been studied. TOLED on ITOsubstrates and on thin Au films exhibit very low onset voltages of 2.2 V. Bothtypes show about 30% transparency in the VIS light region and emit orange lightwith a peak wavelength of 608 nm from either side with a total EQE of about 9%(measured at 1000 cd/m2 in sum). The third type of TOLED wasfabricated with an inverted structure, with the aim to further increaseoperational lifetime by burying the reactive LiF/Al electron injection layer(EIL). This will make the EIL less accessible for oxygen and moisture. Ourresults show difficulties in electron injection when depositing the organicstack on Al/LiF, which may be attributed to an insufficient thermal activationof the EIL.