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16 October 2007 Highly efficient fully transparent inverted OLEDs
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Abstract
One of the unique selling propositions of OLEDs is their potential to realize highly transparent devices over the visible spectrum. This is because organic semiconductors provide a large Stokes-Shift and low intrinsic absorption losses. Hence, new areas of applications for displays and ambient lighting become accessible, for instance, the integration of OLEDs into the windshield or the ceiling of automobiles. The main challenge in the realization of fully transparent devices is the deposition of the top electrode. ITO is commonly used as transparent bottom anode in a conventional OLED. To obtain uniform light emission over the entire viewing angle and a low series resistance, a TCO such as ITO is desirable as top contact as well. However, sputter deposition of ITO on top of organic layers causes damage induced by high energetic particles and UV radiation. We have found an efficient process to protect the organic layers against the ITO rf magnetron deposition process of ITO for an inverted OLED (IOLED). The inverted structure allows the integration of OLEDs in more powerful n-channel transistors used in active matrix backplanes. Employing the green electrophosphorescent material Ir(ppy)3 lead to IOLED with a current efficiency of 50 cd/A and power efficiency of 24 lm/W at 100 cd/m2. The average transmittance exceeds 80 % in the visible region. The on-set voltage for light emission is lower than 3 V. In addition, by vertical stacking we achieved a very high current efficiency of more than 70 cd/A for transparent IOLED.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Meyer, T. Winkler, S. Hamwi, S. Schmale, M. Kröger, P. Görrn, H.-H. Johannes, T. Riedl, E. Lang, D. Becker, T. Dobbertin, and W. Kowalsky "Highly efficient fully transparent inverted OLEDs", Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 66550L (16 October 2007); https://doi.org/10.1117/12.734051
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