Thermal properties of organic light-emitting diodes

Thermal management is important for the efficient operation of organic light-emitting diodes (OLED, or PHOLED) at high brightness, with the device operating temperature influencing both lifetime and performance. We apply a transmission-matrix approach to analytically model the effects of thermal conduction, convection and radiation on OLED temperature. The model predictions match experiment without requiring the use of fitting parameters. This allows for the simulation of the thermal response of various device architectures, materials combinations and environmental factors under a variety of operating conditions. Using these simulations, we find that 87% of the heat is dissipated through the air space adjacent to the glass package cap. Furthermore, an air gap between the device cathode and cap provides a significant thermal impedance.Minimizing the thickness of the internal air gap can lead to nearly room temperature operation, even at very high brightness. 2012 Elsevier B.V. All rights reserved. The high efficiency, large color gamut, and ease of manufacture of organic light-emitting diodes (OLEDs) have led to their practical application in flat panel displays [1]. More recently, large-area white OLEDs have also been found suitable for lighting applications, with devices already exceeding the efficiency of fluorescent panels [2,3]. However, the lifetime of OLEDs operated at the surface luminance required for lighting (3000 cd/m or higher) is sensitive to temperature, with 1.65 longer lifetime for a decrease of 10 K [4]. Accurate methods for modeling and designing temperature-tolerant device structures and luminaries, therefore, are needed. Here, we apply a recently introduced matrix method to quantify one-dimensional heat-transfer from the active region of a multi-layer, packaged OLED by fully describing the effects of conduction, convection and radiation. In an extension of previous work [5], we employ an analytical treatment for the effects of convection, allowing for an . All rights reserved. ical Engineering and