本論文主旨為利用聚對苯乙烯衍生物“Super Yellow”製作光學微共振腔和發光二極體(organic light-emitting diode, OLED)微共振腔，探討超強耦合物理和發光現象。理論上，在共振腔內若光子與在材料激發態(激子)之間產生強烈的能量耦合，將產生半光半物質之混成態，即偏極子(polariton)能態。在光子與激子能量相近時產生不同偏極子色散分支的能量差則稱為拉比分裂，可反應出耦合的強度。當拉比分裂能量超過激子能量20%以上則稱為超強耦合的狀態。 首先我們通過調整Super Yellow膜厚製作光學共振腔，探討主動層厚度與耦合強度的關係，並觀察偏極子光致發光變化。我們使用Hopfield Hamiltonian分析能量色散，證明足夠厚度的Super Yellow可產生超強耦合效應，且當設計厚度使偏極子下支能態匹配Super Yellow的發光峰能量，激子到偏極子的能量轉移和光致發光效率最高。進一步在OLED共振腔元件製作上，我們固定Super Yellow膜厚，利用ZnO和polyethylenimine (PEI)的混合層作為電子注入層，調整其比例提升元件的外部量子效率。在 ZnO:PEI的重量百分比為1:0.33的條件和25 nm厚度下，我們得到最佳化之超強耦合OLED元件，其最高外部量子效率2.79%，最高亮度達到6255 cd/m2，且拉比分裂能量為0.92 eV，與激子能量的比值達到33%。 ;This thesis exploited phenyl-substituted poly(para-phenylene vinylene) copolymer “Super Yellow” as the emissive layer to fabricate optical microcavity and OLED microcavity, and discuss ultrastrong coupling physics and emission phenomenon. In theory, when photon and exciton strongly interact in a cavity, a hybrid state, i.e., the so-called polariton state, will be generated. The Rabi splitting energy between different polariton dispersion branches is an indication of coupling strength, which occurs when the photon and exciton modes have the same energy. Ultrastrong coupling regime is reached when the Rabi splitting energy exceeds 20% of the exciton energy. First, we study the optical microcavities with different Super Yellow film thicknesses to understand the thickness effect on the coupling strength and polariton photoluminescence (PL). By using Hopfield Hamiltonian to analyze the polariton dispersion curves, we demonstrate that a sufficiently thick Super Yellow film can generate ultrastrong coupling. When the thickness is designed to match the lower polariton mode and emission peak of Super Yellow, the highest transfer efficiency from exciton to polariton and strongest PL emission can be obtained. We further fabricate OLED microcavity by fixing the Super Yellow film, and adjust the ZnO:polyethylenimine (PEI) blend film as the electron injection layer to optimize the device efficiency. When using the ZnO:PEI film with 1:0.33 blend ratio and 25 nm thickness, we demonstrate an optimal ultrastrongly coupled OLED with the maximum external quantum efficiency of 2.79% and the highest luminance of 6255 cd/m2, while the Rabi splitting energy is 0.92 eV, corresponding to 33% of exciton mode energy.
