Characterization and optimization of OLED materials and layer sequences

Wolfgang Kowalsky; Edo Becker; Torsten Benstem; Hans-Hermann Johannes; Dirk Metzdorf; H. Neuner; Joerg Schoebel

doi:10.1117/12.416894

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2 February 2001 Characterization and optimization of OLED materials and layer sequences

Wolfgang Kowalsky, Edo Becker, Torsten Benstem, Hans-Hermann Johannes, Dirk Metzdorf, H. Neuner, Joerg Schoebel

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Proceedings Volume 4105, Organic Light-Emitting Materials and Devices IV; (2001) https://doi.org/10.1117/12.416894
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

Abstract

In recent years, considerable effort has been put into the development of light emitting devices based on evaporated layers of organic semiconductors. To date, matrix displays consisting of organic light emitting diodes (OLEDs) have been brought into marketable commodity. OLED matrix displays offer high contrast, wide viewing angle and a broad temperature range at low power consumption. In contrast to polymer devices, OLEDs are processed in ultrahigh vacuum systems. The organic source materials are sublimated from effusion cells. Due to the sensitivity of organic thin films, device structuring by conventional etching techniques is not feasible and alternative structuring techniques were developed. Electrical current in organic devices is limited by the low conductivity of organic semiconductors and by energy barriers at the metal-organic semiconductor interface. Photoelectric measurements facilitate the determination of barrier height differences between various electrode setups. Further insight in the energy band alignment at organic heterointerfaces are gained by ultraviolet photoelectron spectroscopy (UPS). In addition to widely employed electrical (I-V, C-V) and optical (P-I) measurements, thermally stimulated current (TSC) and luminescence (TSL) allow the characterization and a more detailed understanding of carrier traps and charge transport in organic devices. Energy transfer in a doped OLED emitting layer can be investigated by time-resolved photoluminescence measurements.

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Wolfgang Kowalsky, Edo Becker, Torsten Benstem, Hans-Hermann Johannes, Dirk Metzdorf, H. Neuner, and Joerg Schoebel "Characterization and optimization of OLED materials and layer sequences", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); https://doi.org/10.1117/12.416894

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