The influence of heat dissipation on the performances of organic light-emitting diode (OLED) is investigated by measuring junction temperature and by calculating the rate of heat flow. The calculated rate of heat flow reveals that the key factors include the thermal conductivity, the substrate thickness, and the UV glue. Moreover, the use of copper substrate can effectively dissipate the joule heat, which then reduces the temperature gradient. Finally, it is shown that the use of a high thermal conductivity thinner substrate can enhance the thermal conductivity of OLED and the luminance efficiency as well.
The triple-metal-layer periodic structures in the anode for top-emission organic light-emitting diodes (TEOLEDs) are reported in this paper. The anode consists of aluminum (Al) and nickel/gold (Ni/Au) periodic structures. The Al is used for high reflectivity and Ni/Au for high work function by enhancing the hole injection from the anode into the organic hole injection layer. The Ni and Au work functions were measured at 5.3 and 5.1 eV, respectively, which were higher than that of a single Al layer at 4.2 eV. This two pair Ni/Au anode device exhibits high reflectivity and reveals the microcavity effect to increase luminescence efficiency. The optimum current efficiency with the two pair Ni/Au anode is increased to 7.99 cd/A compared with the one pair Ni/Au anode (6.85 cd/A) and three pair Ni/Au anode (5.07 cd/A).
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