- 學位論文
利用溶液製程與轉印技術製作多層小分子有機發光二極體
Fabrication of Multilayer Small Molecule Organic Light Emitting Diodes Using Solution-Based Processing and Stamping
摘要
本研究利用PEDOT:PSS作為電洞注入層，發光層則使用具有雙極性特性及能量轉移效率較高的主體材料26DCzPPY，並摻雜藍色磷光材料FIrpic，以溶液製程方式進行旋塗成膜。接著準備另一轉貼基板PDMS，將PDMS進行表面處理，使溶解後之TPBi溶液旋塗於PDMS轉貼板上，再以加壓加熱轉貼方式將TPBi有機薄膜轉印於發光層上方，而轉印製程上溫度控制，則是一大重要關鍵，須考慮到有機薄膜的玻璃轉移溫度(glass transition temperature, Tg)，避免有機薄膜由非晶性薄膜再結晶形成結晶性薄膜，另一方面須考慮到薄膜與薄膜之間接觸(contact)特性，溫度太低則造成接觸特性差，溫度太高則會造成薄膜結晶化，因此必須調整一最佳化參數，達成轉印技術於元件之上，最後蒸鍍LiF/Al電極，成功獲得一可全溶液製程高效率藍色磷光有機發光二極體，在電流密度20 mA/cm2下，發光亮度為1620 cd/m2，電流效率8.7 cd/A。研究亦利用Ir(btp)2(acac)紅光材料摻雜於發光層內，並調整紅色摻雜濃度以製作雙波段白色磷光有機發光二極體，其元件在電流密度20 mA/cm2下，發光亮度為1060 cd/m2，電流效率為5.55 cd/A。電壓從8 V增加至12 V，CIE x色偏僅 (0.01)。
並列摘要
At first PEDOT:PSS is spin-coated on ITO-coated glass substrate as hole injection layer. Secondly, 26DCzPPY as host material and FIrpic as blue dopant are mixed and dissolved in toluene to form an emitting solution which then is spin-coated onto PEDOT:PSS layer. As known, 26DCzPPY is a bipolar material and has high energy transfer efficiency to transfer triplet energy to phosphorescent dopant. Next poly(di-methylsilane) (PDMS) stamp is used for transferring the electron transporting layers (TPBi) onto the 26DCzPPY film. An intermediate UV ozone treatment is introduced to temporarily modify the PDMS surface; therefore, the solution-based TPBi film can be uniformly formed on top of the PDMS surface. After that, the TPBi film on the PDMS stamp is transfer-printing onto 26DCzPPY:FIrpic emitting layer with suitable heating and pressing. In stamping process, heating treatment is the most important key to achieve successful device. If heating temperature was too high (over glass transition temperature Tg), it maybe crystallize the amorphous organic thin film to become crystalline thin film. Other hand, the quality of interface contact between organic films would be decreased due to heating treatment with low temperature. In our research, heating treatment temperature was optimized at 120 ℃ to reach the best quality of organic films. Finally, LiF/Al is thermally evaporated as cathode electrode. A fully solution-based processing is successfully established to fabricate high efficiency blue SM-OLED. At current density of 20 mA/cm2, the luminance and efficiency of 1620 cd/cm2 and 8.7 cd/A, respectively, are obtained. We fabricate a SM-OLED with solution-based processing, showing that the organic-organic interface formed by the transfer process does not significantly affect device performance. The benefits of both the efficiency promoted by the multilayer structures and the low cost fabrication made possible by the solution-based processing can be obtained by employing the stamping procedure to form multi-layers in SM-OLEDs. In this study, Ir(btp)2(acac) was used as red material doped in the light-emitting layer, and then its concentration was optimized for generating a complementary white phosphorescent organic light emitting diodes. At the current density of 20 mA/cm2, luminance of 1060 cd/m2 and current efficiency of 5.55 cd/A was obtained along with insignificant shift CIEx only (0.01) when allied voltage increased from 8 V to 12 V.
參考文獻
延伸閱讀
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