Experimental proof of Joule heating-induced switched-back regions in OLEDs
Open Access
- 10 January 2020
- journal article
- research article
- Published by Springer Science and Business Media LLC in Light: Science & Applications
- Vol. 9 (1), 1-10
- https://doi.org/10.1038/s41377-019-0236-9
Abstract
Organic light-emitting diodes (OLEDs) have become a major pixel technology in the display sector, with products spanning the entire range of current panel sizes. The ability to freely scale the active area to large and random surfaces paired with flexible substrates provides additional application scenarios for OLEDs in the general lighting, automotive, and signage sectors. These applications require higher brightness and, thus, current density operation compared to the specifications needed for general displays. As extended transparent electrodes pose a significant ohmic resistance, OLEDs suffering from Joule self-heating exhibit spatial inhomogeneities in electrical potential, current density, and hence luminance. In this article, we provide experimental proof of the theoretical prediction that OLEDs will display regions of decreasing luminance with increasing driving current. With a two-dimensional OLED model, we can conclude that these regions are switched back locally in voltage as well as current due to insufficient lateral thermal coupling. Experimentally, we demonstrate this effect in lab-scale devices and derive that it becomes more severe with increasing pixel size, which implies its significance for large-area, high-brightness use cases of OLEDs. Equally, these non-linear switching effects cannot be ignored with respect to the long-term operation and stability of OLEDs; in particular, they might be important for the understanding of sudden-death scenarios.Keywords
Funding Information
- Deutsche Forschungsgemeinschaft (RE 3198/6-1, RE 3198/6-1, RE 3198/6-1, EXC-2046/1, EXC-2046/1, EXC-2046/1)
- Cusanuswerk Foundation
This publication has 37 references indexed in Scilit:
- Investigation of large-area OLED devices with various grid geometriesOrganic Electronics, 2013
- Passive cooling of large-area organic light-emitting diodesOrganic Electronics, 2013
- Hydrofluoroethers as heat-transfer fluids for OLEDs: Operational range, stability, and efficiency improvementOrganic Electronics, 2012
- Recent Advances in White Organic Light‐Emitting Materials and Devices (WOLEDs)Advanced Materials, 2010
- White organic light-emitting diodes with fluorescent tube efficiencyNature, 2009
- Impact of Joule heating on the brightness homogeneity of organic light emitting devicesApplied Physics Letters, 2007
- Comparison of Charge‐Carrier Transport in Thin Films of Spiro‐Linked Compounds and Their Corresponding Parent CompoundsAdvanced Functional Materials, 2006
- Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilationPhysical Review B, 2000
- The effect of local non-uniformities on thermal switching and high field behaviour of structures with chalcogenide glassesSolid-State Electronics, 1975
- Fluctuations of the Numbers of Electrons and Holes in a SemiconductorProceedings of the Physical Society. Section B, 1955