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 ra...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.展开更多
基金supported in part by the German Research Foundation(DFG)within the Cluster of Excellence Center for Advancing Electronics Dresden(cfaed)and the DFG project EFOD(Grant No.RE3198/6-1)supported by the DFG under Germany's Excellence Strategy-MATH+:The Berlin Mathematics Research Center(EXC-2046/1-project ID:390685689)via projects AA2-1 and AA2-6+1 种基金Open Access Funding by the Publication Fund of the TU Dresdenfunding from the Cusanuswerk Foundation.
文摘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.
