2007-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/705632摘要：有機電激發光元件具備可製作於可撓式基版上及適用大尺寸製程等優點，為一深具潛力之影像顯示及白光照明技術。在有機材料的開發上，以雙載子傳輸有機材料作為發光層之主體材料，其特點包括：（1）可擴大有機電激發光元件復合區，延長使用壽命；（2）電子及電洞均可在發光層中運動，造成元件電流之上升，驅動電壓下降及功率損耗降低；以及（3）許多的藍光、白光及燐光元件之發光層均具備雙載子傳輸特性。 本實驗室過去曾以雙載子傳輸有機材料作為發光層之主體材料，得到下列成果：（1）將有機電激發光元件之壽命提高六倍，（2）建立一套光電模擬程式，並與實驗取得極佳之一致性，以及（3）以薄摻雜層研究其光電特性，發現該薄摻雜層可降低驅動電壓，並利用此技術製成低電壓及高效率之白光有機電激發光元件。然而，該技術仍存在以下問題：（1）由於電子及電洞密度於空間之重疊性較差，導致電流效率較傳統元件低，（2）老化動態並未定量化探討，（3）模擬使用之材料參數，並非完全由實驗求得，以及（4）尚未建立一設計流程以優化元件。 因此，本計畫之目的，係為：（1）利用不同之有機材料及混和比例做為主體材料，插入適當寬度及濃度之螢光或燐光摻雜物，並適當插入電洞及電子阻隔層，以提升電流效率，且維持低電壓及長壽命的優點，（2）以變溫光電特性量測及外部量子效率量測，觀測於不同條件操作之不同時間下，元件光電特性之改變，直接觀測元件老化過程，以釐清其物理機制，（3）以變溫電性量測、暫態電激發光及飛行時間量測等，直接量得載子之注入及傳輸特性，將理論基礎及基本材料參數架構完備，（4）建立一套元件設計規則，控制發光區之位置及放光波長，以達到壽命、效率、色度座標及演色性之最佳化，並應用於影像顯示及白光照明領域。 <br> Abstract: Organic light emitting devices (OLEDs) is one of the promising display and lighting technologies due to the advantages of high brightness, high contrast, and potentially low cost. Such a device can be fabricated on a flexible substrate and suitable for the roll-to-roll process. However, since the efficiency is low and the lifetime is short, the applications of OLED are limited to the small displays of the consumer electronics, such as mobile phones and digital cameras. To improve the device performances, ambipolar organic materials are used as the host of the emitting layer (EML) since: (1) the recombination zone is broaden which elongates the device lifetime; (2) hole and electron can both transport in the EML which increases the current density, decreases the driving voltage and lowers the power consumption; and (3) several important blue, white, and phosphorescent EMLs exhibit the ambipolar transport characteristics. In our previous researches, we have co-evaporated the hole- and electron-transport materials as the host of the EML which was called the mixed-host (MH) technique and exhibited the ambipolar characteristics. By using MH-EML, we have achieved: (1) elongation of the operation lifetime by six and three times for blue- and green-OLEDs, respectively; (2) optical and electrical simulations of carrier distributions, emission zone, and spectral shift based on continuity, Poisson’s, drift-diffusion current density, and Maxwell’s equations which showed good agreements with experimental results; and (3) using a thin probe to investigate the optical and electrical characteristics in the MH-EML. We also found that the thin-probe in the ambipolar EML helps to reduce the driving voltage since it increases the recombination current. Hence, a high efficiency white-OLED with a low driving voltage was fabricated by selectively doping a thin yellow rubrene in the blue EML. Although we have qualitatively and quantitatively investigated the ambipolar EML, there is still much room for investigation, for examples: (1) the current efficiency of the ambipolar-OLED is lower than that of the conventional heterojunction device due to the worse spatial overlap between the electron and hole distributions; (2) aging dynamic in such a device is still not clear; (3) some material parameters in our simulations are not obtained directly from experiments but from the numerical fittings; and (4) a design rule should be established to optimize the OLED for display and lighting applications, respectively. Hence, the objectives of the project include: (1) improvement of the current efficiency without the tradeoff of the driving voltage and lifetime by engineering the EML host materials, mixing ratios, dopant materials (including fluorescent and phosphorescent), conce有機電激發光元件OLED