根基於咔唑分子之主體及發光體材料於乾式及濕式有機發光二極體之應用

有機發光二極體（OLED）由於在高品質顯示器和固態照明中的應用日益增加而備受矚目。因OLED的固有優勢，促使工程師和科學家們付出許多努力，將這項技術用於下一代消費電子產品；其顯著的優點包括低功耗、散熱、色域可調、元件製程容易、可撓及形狀可隨所需而改變。使此項技術持續發展的是新穎有機材料的開發，其在於發展高性能元件上扮演極重要的角色；探尋幾種分子結構，咔唑分子本身具有高熱穩定性、良好的電洞遷移率、容易合成的路徑及易於結構調整，咔唑分子已被用於設計電洞傳輸、主體和發光材料，因此，根基於咔唑分子的OLED元件已展現顯著進步。本研究中使用根基於咔唑之主體和發光材料的使用。咔唑合成並透過添加官能基進行改質。兩個提供電子的甲氧基與咔唑核連接，使其分子具有非常好的電洞遷移率、非常寬的光學能階差及高三重態能量。利用這些性質，該新穎材料能用作為磷光有機發光二極體中的主體材料。因此，透過摻雜綠色磷光染料Ir(ppy)3來研製OLED元件，並透過溶液和熱蒸鍍製程。此兩種元件皆表現出高發光效率，其中乾式製程元件，於100 cd/m2 下之能量效率52.7 lm/W、電流效率為59.4 cd/A、外部量子效率16.4％及最大亮度為 36,810 cd/m2；而使用高電洞遷移率之咔唑電洞傳輸材料，其元件性能能量效率提升至62.8 lm/W、電流效率61.0 cd/A、外部量子效率17.2% 及最大亮度47,890 cd/m2；此外，基於咔唑主體元件在1,000cd/m2下的效率滾降非常低。本研究亦開發一種根基於咔唑的新穎深藍螢光發光材料，其三苯胺作為供電子基團，而腈官能基作為接受電子基團；這些取代基的加入，改變了材料的HOMO和LUMO能階，因此，所得材料擁有非常寬的能隙。為了了解其光電表現，將其摻雜在雙極性主體中，此新穎發光材料顯示出其具有濕式和乾式特性。與國家電視系統委員會標準相比，溼式製程元件為高效率之深藍光，其色彩飽和度極高，超過100%。

關鍵字

有機發光二極體；磷光；螢光；濕式製程；乾式製程；咔唑分子

並列摘要

Organic light-emitting diodes (OLEDs) have drawn enormous recognition due to their potential applications in high-end flat-panel displays and solid-state lightings. The intrinsic advantages of OLEDs have impelled the engineers and scientists to put tremendous research effort to exploit this technology for next generation consumer electronics. The notable advantages include low power consumption and heat dissipation, color gamut a tunablity, easy device fabrication and the potential for flexible, deformable and conformable form factors. What makes this technology ever advancing is development of novel organic materials which plays significant roles in obtaining high efficiency devices with many other desired properties. Amongst several kinds of explored molecular structures, carbazole based molecules have shown significant advancements via developing high performance OLED devices. Carbazole cores intrinsically possess high thermal stability, good hole mobility, facile synthesis routs, easy structural tunability etc. due to such superior characteristics carbazole molecules had been utilized in designing hole transporting, host and emitter materials. The works presented in this thesis demonstrate the use of carbazole based host and emitter materials. A carbazole core is synthesized and modified with the addition of functional groups. Two electron donating methoxy groups were linked to the carbazole core. The resulted molecule possesses very good hole mobility as well as very wide optical bandgap and high triplet energy. With these properties, the novel material attains the potential to be used as a host material in phosphorescent organic light emitting diodes. Therefore, an OELD device was fabricated by doping phosphorescent green emitter Ir(ppy)3. The host also shows processability via both solution and thermal evaporation deposition. Both the devices exhibited high electroluminescent efficiencies. At 100 cd/m2, the resultant basic dry-processed device showed efficacy of 52.7 lm/W (59.4 cd/A) and external quantum efficiency of 16.4% with a maximum luminance of 36,810 cd/m2. By employing a high hole mobility carbazole-based hole transport material, the device performance was further enhanced to 62.8 lm/W (61.0 cd/A and 17.2%) with 47,890 cd/m2. The carbazole host based devices experienced very less efficiency roll-off at 1,000 cd/m2. Moreover, the thesis also reports a carbazole based novel deep-blue fluorescent emitter material. A carbazole core based material is functionalized with an electron donating group, triphenylamine and an electron accepting group, carbonitrile. The addition of these substituents modified the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the material. The resultant material shows a very wide band gap. To understand its electroluminescent behavior, it was doped in a bipolar host. The novel emitter material showed both wet- and dry-processabilities. The wet-processed device resulted into high efficiency with deep-blue emission as well as very high color saturation over 100% as compared with the National Television System Committee standard

並列關鍵字

Organic light emitting diode ； phosphorescence ； fluorescence ； wet process ； dry process ； carbazole molecule

參考文獻

53. J. H. Jou, S. M. Shen, M. C. Tang, P. C. Chen, S. H. Chen, Y. S. Wang, C. C. Chen, and C. C. Wang, C. Y. Hsieh, C. C. Lin, C. T. Chen, SPIE, 2013, 8476, 847619; DOI: 10.1117/12.927778

1. http://www.sky-technology.eu/en/displays/oled-displays.html