應用半穿透金屬輔助電子注入層之高效率高飽和度倒置式下發光有機發光二極體

Abstract

為了將n型薄膜電晶體與有機電激發光顯示器結合，我們致力於研發高效率高飽和度的倒置式有機發光二極體元件。在倒置式下發光結構的研究中，我們以ITO作為陰極，Al作為陽極。因此，如何克服電極與有機層之間的能階不匹配，為本篇論文之研究重點。 我們開發出了新型n-i-p結構以BPhen: 10% Cs2CO3作為n型摻雜層，以NPB: 33% WO3/ WO3 的雙層結構作為p型摻雜層。應用此結構的綠光螢光IBOLED有效的降低了載子注入的能障，得到比傳統元件更低的操作電壓，且提升了27%的電流效率。應用此結構的深藍光元件效率可達5.6 cd/A，外部量子效率5.3% ，CIEx.y = (0.14, 0.13)。 為了更有效的改善ITO陰極的電子注入能力，我們以半透明的Ag薄膜作為電子注入層。除了增強電子注入能力，促進載子平衡以增加激發子再結合率，提升內部量子效率外，同時還能藉由該電子注入層半穿透的光學特性，利用微共振腔效應來增加出光率，達到更高的外部量子效率。我們並將此應用於IOLED的電子注入層命名為「半穿透金屬輔助電子注入層( Semi-transparent Metal-assisted Electron Injection Layer, SM-EIL)」。藉由SM-EIL 綠光螢光IBOLED效率可達24 cd/A 、12.9 lm/W 、E.Q.E.= 6.2%，色度座標CIEx,y = (0.24, 0.71)。

Study of Inverted type OLEDs has become increasingly important and timely for the realization of a-Si TFT driven large panel AMOLED such as OLED TV. We discovered that both efficient and color-saturated inverted bottom-emission OLED can be achieved by using a novel n-i-p structure with a bilayer HIL and the insertion of a novel semi-transparent metal-assisted electron injection layer (SM-EIL) between ITO and the n-doped ETL. The SM-EIL is found to create a beneficial microcavity effect which can be utilized to enhance color saturation without adversely impacting on its electrical property. The efficiency of this IBOLED was boosted up to 24 cd/A, 12.9 lm/W at a drive current density of 20 mA/cm2 and achieved an external quantum efficiency of 6.2% with a CIEx,y coordinate (0.24, 0.71), which is among the best that have been reported for the green C545T fluorescent dye-doped devices.