透過您的圖書館登入
IP:3.234.253.152
  • 學位論文

濕式製程製作之高效率藍光有機發光二極體

High-Efficiency Blue Organic Light-Emitting Diodes via Solution-Process

指導教授 : 周卓煇
若您是本文的作者,可授權文章由華藝線上圖書館中協助推廣。

摘要


本研究,利用濕式製程,製作一系列具單一發光層之高效率藍光有機發光二極體(Organic Light Emitting Diodes, OLEDs),所製備元件,可分為三部分作探討。 第一部分:我們使用一新穎分子型主體3,5-di(9H-carbazol-9-yl)tetraphenylsilane(SimCP2),並利用濕式製程製作此主體組成的發光層,可獲得一高效率藍光OLED,其在亮度100 cd/m2下,電流效率有41.2 cd/A、外部量子效率21.0%、能量效率24.9 lm/W;在1,000 cd/m2下有31.1 cd/A、15.8%、15.4 lm/W;此元件之高效率,部分歸因於使用此分子主體,其具有寬三重態能隙、高電洞電子移動率、雙極性傳輸特性以及高玻璃轉換溫度等特性;除了主體材料本身的優異物性,濕式製程的使用,亦是獲得高效率元件的關鍵因素,因該製程可使主客體分子均勻分佈在發光層中,有效幫助主客體間能量轉移;還有,元件在高亮度時,可經由電子阻擋層的使用,使效率獲得顯著強化。 第二部分:我們發表一新穎寡聚物主體,其具有寬三重態能隙及高電子移動率等特性;利用濕式製程製作此主體組成的發光層,可獲得一高效率藍光OLED,其在亮度231 cd/m2下,電流效率有40.4 cd/A、外部量子效率21.6%、能量效率28.2 lm/W;在1,000 cd/m2下有24.7 cd/A、10.3%、15.5 lm/W;此高效率,可能歸因於此主體的寬三重態能隙,可有效幫助主客體間的能量轉移;再者,此主體的高電子移動率,可幫助電子傳輸而強化元件載子注入平衡;為進一步提升元件效率,可於發光層旋塗前,預先加熱發光溶液至一高溫,使元件效率在亮度124 cd/m2下,達42.6 cd/A、22.9%、29.7 lm/W;在1,000 cd/m2下有28.8 cd/A、15.4%、17.8 lm/W。 第三部分:我們發表一系列新穎高表面電荷奈米點,將其摻混於非發光層中,可大幅強化本身已為高效率藍光OLED的性能;其中,藉由胺根奈米點(Amino-functionalized PND, Am-PND)的使用,一效率在100 cd/m2下已有18.0 lm/W高的藍光元件,可倍增至35.8 lm/W;在照明應用下的亮度,例如:1,000 cd/m2,元件效率可由原先的12.4 lm/W,強化至21.2 lm/W,增幅達71%;這些高表面電荷奈米點,可產生阻擋或侷限電洞的效果,有效調制電洞傳輸,避免過多電洞進入至發光層而發生載子注入不平衡;再者,經由奈米點高表面電荷產生的強烈斥力場或吸引力場,僅有帶足夠能量的電洞,克服這些障礙,而穿入發光層內更深的距離,並與電子在更寬廣的覆合區中結合,而使元件表現更高亮度、且有更高效率。

並列摘要


In this study, we demonstrate a series of high-efficiency blue oganic light emitting diodes with a solution-processed emissive layer. Their result and discussion will be shown in three parts. In the first part, we present a high-efficiency blue organic light-emitting diode (OLED) with a solution-processed emissive layer composing a melucular-based host of 3,5-di(9H-carbazol-9-yl) tetraphenylsilane. The device exhibits a current efficiency of 41.2 cd/A with an external quantum efficiency (EQE) of 21.0% and power efficiency of 24.9 lm/W at 100 cd/m2 or 31.1 cd/A (15.8%, 15.4 lm/W) at 1,000 cd/m2. The high efficiency is partly attributed to the use of a novel molecular host, which possesses wide triplet band gap, high carrier mobility, ambipolar transport property and high glass transition temperature. Besides the intrinsically good physical properties, solution-process also plays an important role to fabricate the high-efficiency device, since it could make the molecular distribution of host and guest homogeneous in the emissive layer to facilitate host-to-guest energy transfer. Moreover, the device efficiency at higher brightness could be markedly enhanced by using an electron-blocking layer. In the sencond part, we also demonstrate a high-efficiency blue OLED with a solution-processed emissive layer composing an oligomeric host of 3-(carbazol-9-ylmethyl)-3-methyloxetane that possesses high triplet-energy and especially high electron-mobility. The device exhibits a current efficiency of 40.4 cd/A with an external quantum efficiency (EQE) of 21.6% and power efficiency of 28.2 lm/W at 231 cd/m2 or 24.7 cd/A (10.3%, 15.5 lm/W) at 1,000 cd/m2. The high efficiency may be attributed to the host that possesses a wide triplet band-gap, effectively facilitating energy-transfer from the host to guest. Moreover, the high electron-mobility favors the transport of electron, resulting to a more balanced carrier-injection in the emissive layer. The device efficiency has been further enhanced to 42.6 cd/A (22.9%, 29.7 lm/W) at 124 cd/m2 or 28.8 cd/A (15.4%, 17.8 lm/W) at 1,000 cd/m2 by pre-heating the emissive solution at elevated temperature before spin-coating. In the last part, the efficiency of highly efficient blue OLEDs has been substantially advanced through the use of high surface-charge nanodots embedded in a non-emissive layer. Amonst, the blue OLED’s markedly high initial power efficiency of 18.0 lm/W at 100 cd/m2 was doubled to 35.8 lm/W when an amino-functionalized polymeric nanodot was employed. At high luminance, such as 1,000 cd/m2, used for illumination applications, the efficiency was improved from 12.4 to 21.2 lm/W showing a significant enhancement of 71%. The incorporated highly charged nanodots are capable of effectively modulating the transportation of holes via a blocking or trapping mechanism, preventing excessive holes from entering the emissive layer and the resulting carrier-injection imbalance. Furthermore, in the presence of a high-repelling or dragging field arising from the highly charged nanodots, only those holes with sufficient energy are able to overcome the included barriers, causing them to penetrate deeper into the emissive layer. This penetration leads to carrier recombination over a wider region and results in a brighter emission and, therefore, higher efficiency.

並列關鍵字

OLED host nano dot

參考文獻


[111] Q. Niu, Y. Shao, W. Xu, L. Wang, S. Han, N. Liu, J. Peng, Y. Cao, J. Wang, Org. Electron. 2008, 9, 95.
[20] (a) M. H. Tsai, H. W. Lin, H. C. Su, T. H. Ke, C. C. Wu, F. C. Fang, Y. L. Liao, K. T. Wong, C. I. Wu, Adv. Mater. 2006, 18, 1216; (b) M. H. Tsai, Y. H. Hong, C. H. Chang, H. C. Su, C. C. Wu, A. Matoliukstyte, J. Simokaitiene, S. Grigalevicius, J. V. Grazulevicius, C. P. Hsu, Adv. Mater. 2007, 19, 862.
[85] C. F. Chang, Y. M. Cheng, Y. Chi, Y. C. Chiu, C. C. Lin, G. H. Lee, P. T. Chou, C. C. Chen, C. H. Chang, C. C Wu, Angew. Chem. Int. Ed. 2008, 47, 4542.
[59] C. C. Oey, A. B. Djurisic, C. Y. Kwong, C. H. Cheung; W. K. Chan, J. M. Nunzi, and P. C. Chui, Thin Solid Films 2005, 492, 253.
[24] P. I. Shih, C. H. Chien, C. Y. Chuang, C. F. Shu, C. H. Yang, J. H. Chen, Y. Chi, J. Mater. Chem. 2007, 17, 1692.

延伸閱讀