具微共振腔結構之上發光型有機發光元件光學模擬分析

Abstract

在這篇論文中，我們使用一個電磁模型模擬上發光型有機發光二極體(TOLED)的光學特性。上發光型有機發光元件可被視為一維的Fabry-Perot微共振腔，微共振腔效應造成發光強度和光譜隨元件結構和觀察視角產生不可忽略之變化。我們設計三種不同的陰極結構，分別為氧化銦錫、銀和在銀上方覆蓋一層硒化鋅的上發光型有機發光元件，計算元件在正上方強度和所有光通量總和。使用硒化鋅覆蓋銀做為陰極的元件，在正上方強度和總流量最佳化後，可獲得比其它兩種陰極元件個別最佳化後更高的出光量，而氧化銦錫則是最低。當元件在正上方強度最佳化後，其光譜較不會隨視角而偏移，而當元件在總光通量最佳化後，其光譜隨視角增大會明顯往短波長偏移。 我們利用元件正上方強度最佳化後，其光譜較不會隨視角改變的特性來調變發光光譜。此外，我們提出一新結構，係為置入一層硒化鋅在金屬鏡面和金屬陽極間，藉由改變硒化鋅的厚度會導致陽極的相位及反射率改變而使光譜偏移，隨著硒化鋅的厚度改變，光譜會隨之改變。藉由此特性，我們可以獲得較純的紅、綠、藍光元件。

In this thesis, we use a rigorous electromagnetic model to investigate the optical properties of top-emitting organic light-emitting device (TOLED). TOLED can be regarded as a one dimensional Fabry-Perot microcavity because the total multi-layer thickness is on the order of visible wavelength. The intensity and spectral distribution are strongly dependent on the device structure and viewing angle. We calculate the optical characteristics of TOLEDs with three different cathode materials which are ITO, silver, and silver capped with ZnSe, to optimize the output intensity at normal direction and the total output flux. The cathode consists of sliver capped with ZnSe has the maximum normal direction intensity and total flux, while the ITO case has the lowest. The normal direction optimized EL spectra are independent of the viewing angle, while the flux optimized EL have obviously blue-shift. For better viewing angle characteristic, we first optimize the device at the normal direction, then, tune the total optical length by changing the phase caused by the anode to tune the EL spectrum. A ZnSe layer is inserted between the anode and the metal mirror to change the anode phase and reflectivity. When varying the ZnSe thickness at the anode side, the phase-shift caused by the anode and the total optical length L change. With increasing the ZnSe layer, the EL spectrums have obviously red shift, and still angle-independent. Besides, with thick ZnSe thickness, the reflectivity of anode slightly increases and result in higher output intensity. By using this methodology, pure RGB devices can be obtained.