School of Electrical Engineering, KAIST , Daejeon 34141, Republic of Korea.
Division of Instrument Development, Korea Basic Science Institute , Daejeon 34133, Republic of Korea.
ACS Appl Mater Interfaces. 2017 Aug 16;9(32):27062-27072. doi: 10.1021/acsami.7b06076. Epub 2017 Aug 2.
In this study, a new and efficient dielectric-metal-dielectric-based thin-film encapsulation (DMD-TFE) with an inserted Ag thin film is proposed to guarantee the reliability of flexible displays by improving the barrier properties, mechanical flexibility, and heat dissipation, which are considered to be essential requirements for organic light-emitting diode (OLED) encapsulation. The DMD-TFE, which is composed of AlO, Ag, and a silica nanoparticle-embedded sol-gel hybrid nanocomposite, shows a water vapor transmission rate of 8.70 × 10 g/m/day and good mechanical reliability at a bending radius of 30 mm, corresponding to 0.41% strain for 1000 bending cycles. The electrical performance of a thin-film encapsulated phosphorescent organic light-emitting diode (PHOLED) was identical to that of a glass-lid encapsulated PHOLED. The operational lifetimes of the thin-film encapsulated and glass-lid encapsulated PHOLEDs are 832 and 754 h, respectively. After 80 days, the thin-film encapsulated PHOLED did not show performance degradation or dark spots on the cell image in a shelf-lifetime test. Finally, the difference in lifetime of the OLED devices in relation to the presence and thickness of a Ag film was analyzed by applying various TFE structures to fluorescent organic light-emitting diodes (FOLEDs) that could generate high amounts of heat. To demonstrate the difference in heat dissipation effect among the TFE structures, the saturated temperatures of the encapsulated FOLEDs were measured from the back side surface of the glass substrate, and were found to be 67.78, 65.12, 60.44, and 39.67 °C after all encapsulated FOLEDs were operated at an initial luminance of 10 000 cd/m for sufficient heat generation. Furthermore, the operational lifetime tests of the encapsulated FOLED devices showed results that were consistent with the measurements of real-time temperature profiles taken with an infrared camera. A multifunctional hybrid thin-film encapsulation based on a dielectric-metal-dielectric structure was thus effectively designed considering the transmittance, gas-permeation barrier properties, flexibility, and heat dissipation effect by exploiting the advantages of each separate layer.
在这项研究中，提出了一种新的、高效的基于介质-金属-介质的薄膜封装（DMD-TFE），其中插入了一层 Ag 薄膜，通过提高阻隔性能、机械灵活性和散热性来保证柔性显示器的可靠性，这被认为是有机发光二极管（OLED）封装的基本要求。DMD-TFE 由 AlO、Ag 和嵌入二氧化硅纳米粒子的溶胶-凝胶杂化纳米复合材料组成，水蒸气透过率为 8.70×10-3g/m2/day，在弯曲半径为 30mm 时具有良好的机械可靠性，对应于 1000 次弯曲循环时的 0.41%应变。薄膜封装的磷光有机发光二极管（PHOLED）的电性能与玻璃盖封装的 PHOLED 相同。薄膜封装和玻璃盖封装的 PHOLED 的工作寿命分别为 832h 和 754h。在货架寿命测试中，经过 80 天，薄膜封装的 PHOLED 没有出现性能下降或电池图像上出现暗点。最后，通过将各种 TFE 结构应用于可能产生大量热量的荧光有机发光二极管（FOLED），分析了 OLED 器件的寿命与 Ag 膜的存在和厚度之间的关系。为了证明 TFE 结构之间散热效果的差异，从玻璃基底的背面测量了封装 FOLED 的饱和温度，在所有封装 FOLED 以初始亮度 10000cd/m2 运行足够的热量产生后，封装 FOLED 的饱和温度分别为 67.78、65.12、60.44 和 39.67°C。此外，封装 FOLED 器件的工作寿命测试结果与使用红外摄像机进行的实时温度曲线测量结果一致。因此，通过利用各层的优势，有效地设计了一种基于介质-金属-介质结构的多功能混合薄膜封装，考虑了透光率、透气阻隔性能、灵活性和散热效果。
