在本論文中，我們提出幾種可以有效提昇有機發光二極體效率與色純度之元件結構，包括下發光式白光元件、上發光式綠光元件，以及上發光式白光元件等。其中我們使用螢光材料TBADN作為藍光主體材料，使用螢光材料rubrene作為黃色掺雜材料，並藉由兩者依適當之掺雜比例來獲得具高色純度之白光元件。另一方面我們使用螢光材料Alq3作為綠光主體材料，搭配具高量子效率之綠光掺雜材料C545T，在適當的掺雜比例下可以獲得理想之綠光元件。在下發光式白光元件之製作中，由於藍光主體材料(TBADN)之HOMO能階與電子傳輸層(Alq3)之HOMO能階幾乎相同，所以無法有效讓載子於發光層進行再結合。對此我們利用一Alq3薄層將發光層隔成兩部份，再藉由電洞阻隔層(BCP)之使用，可以將元件之效率從4.26 cd/A提升至5.44 cd/A。但由於BCP層之LUMO能階較接近Rubrene之LUMO能階，造成電子較容易注入Rubrene材料，進而使元件之色度明顯偏向黃光。對此我們再將各發光層拆為掺雜與未掺雜等兩部份，實驗結果顯示元件之色度已有所改善。最後我們再嚐試將發光層之間的Alq3替換成TPBi材料，由於TPBi材料具有較大之HOMO能階，可以有效將電洞阻擋於發光層中，因此元件之效率可以提升至6.09 cd/A，同時元件於9伏操作電壓之CIE座標為(0.32, 0.32)，顯示元件具有相當理想之色純度表現。我們亦使用TBADN藍光主體材料與Rubrene黃光掺雜材料於上發光式白光元件，其元件結構為Ag(200 nm)/NPB(40 nm)/TBADN(13 nm)/ TBADN:(0.5%) Rubrene(9 nm)/TBADN(11 nm)/Alq3(1 nm)/BCP(3 nm)/TBADN(30 nm)/BCP(5 nm)/Alq3(4 nm)/LiF(1 nm)/Ag(20 nm)/ NPB(40 nm)。其中由於TBADN之螢光效率偏低，且藍光對於銀薄膜之穿透率較低，所以我們於元件中設計三層不同厚度之藍光發光層，並用電洞阻隔層(BCP)來提升載子於TBADN層之再結合率，進而補強藍光之發光亮度。元件於5伏操作電壓之CIE座標為(0.35, 0.33)，顯示其具有很理想之白光色度表現。對於上發光式元件之製作，我們採用了銀金屬作為發光元件之陽極，並使用兩種不同之氧化製程來進行銀金屬之表面處理，包括紫外線-臭氧和化學氣相沉積法。其中使用紫外線-臭氧之處理方式，我們發現隨著曝照時間之增加，銀金屬之表面功函數也隨之增加；但同時其表面電阻也會隨之增加，且其表面反射率也會隨之降低，因此我們找到最佳之曝照時間為3分鐘。另一方面，使用化學氣相沉積法之表面處理方式，於不同操作功率以及氧化時間下，發光元件之電性會有明顯之變化，且最佳處理條件為2瓦之操作功率以及6分鐘之氧化時間。在上發光式綠光元件之製作中，我們於Alq3主體材料中掺入高量子效率之C545T材料，同時於元件加入厚度為2 nm之電洞阻隔層(BCP)。由於BCP材料之LUMO能階較接近C545T之LUMO能階，可以提升C545T之發光效率，進而提升綠光元件之整體效率。於1%之掺雜濃度下，綠光元件之電流效率可以從5.19 cd/A有效地提升至19.43 cd/A。另一方面，對於上發光式白光元件之製作，藉由銀陽極之表面氧化處理，元件之電流效率可以從0.56 cd/A提升至1.08 cd/A，且元件於5伏操作電壓下之CIE座標為(0.35, 0.33)，顯示元件具有相當理想之白光色純度表現。

This dissertation presents various organic light-emitting diode (OLED) structures with high efficiency and high color purity, including those with bottom-emission white light, top-emission green light, and top-emission white light. In the design of a white light device, TBADN is used as the blue host and rubrene is used as the yellow dopant. Alq3 is used as the green host, doped with C545T fluorescent material, to obtain a high-performance green light device. The carriers do not recombine effectively in the emission layer because the HOMO energy level of the blue host (TBADN) is almost the same as that of the electron transporting layer (Alq3). The emission layer is divided into two layers by another thin Alq3 layer, and a hole-blocking layer (BCP) is inserted between the emission layer and the electron transporting layer. The current efficiency of white light device was thus improved from 4.26 cd/A to 5.44 cd/A. However, the yellow emission of the device is enhanced by the small energy barrier of LUMO between BCP and rubrene, affecting the color purity of the white light device. The emission layer is divided into a doped layer and an undoped layer, and the experimental results reveal that the color purity of white light is significantly improved. The TBADN and rubrene are also used for top-emission white-OLEDs with the device structure Ag(200 nm)/NPB(40 nm)/TBADN(13 nm)/TBADN: (0.5%)rubrene (9 nm)/TBADN(11 nm)/Alq3(1 nm)/BCP(3 nm)/TBADN(30 nm) /BCP(5 nm)/Alq3(4 nm)/LiF(1 nm)Ag(20 nm)/NPB(40 nm). Since TBADN has low efficiency and the Ag film has low transparency to blue emission, three blue-emitting layers of different thickness and a hole-blocking layer are applied to enhance the blue emission in this work. The CIE coordinate of the device at 5 V indicates that it has high color purity. To fabricate a top-emission device, Ag was used as the anode and two methods of oxidation were utilized to treat the Ag surface. They were the UV-ozone method and PECVD. The work function of Ag increases with the period of exposure in UV-ozone treatment. However, such treatment also increases the sheet resistance and degrades the surface reflectance. The optimal exposure time was around 3 minutes in the experiment performed in this study. However, the performance of an OLED device that has undergone PECVD treatment is determined by the operating power and the oxidation time. The optimal conditions were 2 W for 6 minutes in the experiment herein.
In the fabrication a top-emission OLED, C545T, which has high quantum efficiency, was doped into an Alq3 host and a 2nm-thick hole-blocking layer (BCP) was used deposited on the host. The LUMO of BCP is close to that of C545T and hence increasing the C545T emission and device efficiency. The current efficiency of the green-OLED is improved from 5.19 cd/A to 19.43 cd/A under a 1% doping concentration. The current efficiency of a top-emission white-OLED is improved from 0.56 cd/A to 1.08 cd/A using Ag-anode oxidation. The CIE coordinate of the device at 5 V is (0.35, 0.33), indicating the good color purity of the white-OLED.

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