摘要
在OLED眾多元件中，其中有種發光型態是利用二種不同的分子受激發組合而成，稱之為激發複合態(exciplex)，其原理是利用三重態能階相近的二種材料混和蒸鍍作為發光層或是主體使用，二種材料分子受激發之後，會形成新的能階，這二種材料一個為利於電子傳輸，另一個則為利於電洞傳輸。
本論文包含了二大部份，第一部份主要是針對exciplex主體二種材料之間的混和比例調控，透過各種量測儀器以及數據分析來了解不同混和比例之間的物理特性以及電性，去找出最佳的混和比例；第二部份為改善載子在發光層中的侷限能力，利用類似位能井的結構，將載子有效率的侷限在發光層，進而提高整體元件的效率。
大部分的OLED元件效率與單載子元件的電流密度有極大的關係，為了使其電子和電洞能剛好在發光層相遇，實驗中利用控制蒸鍍率的方式去調控主體材料的混和比例，主要目的是探討改變混和比例對於元件效率的影響性，並利用量測出來的數據進行分析，期盼可以找出影響元件效率最大的主因，進而得到最佳的元件效率，當找出元件最佳的混和比例之後，進一步地透過改變結構去提升元件效率。
第一部份：選用了TCTA和TmPyPB這組exciplex主體材料組合，在不同的混和比例中找出最佳的比例為1:2，整體元件中發光效率達到最高，電流效率可以達到56cd/A，實驗中透過各種量測去找出影響效率的主因，其中包含穿透度、單載子元件電流密度以及吸收光譜-光致發光光譜之重疊比例等等，發現到單載子元件的電流密度是否匹配是最為重要的因素，直接影響到載子再結合的區域以及發光的區域，導致元件效率受到影響。最後利用在主體二側參雜不同色光的材料，去了解到載子的飄移距離及發光區域。
第二部份：利用第一部份最後的實驗得出載子飄移距離過遠，導致發光區域偏移，因此在發光層二側蒸鍍額外的電洞傳輸層和未參雜的客體材料，目的是利用材料本身的能階形成能障，達到類似位能井的效果，讓載子比較容易侷限在發光層內部，利用此方法得到了更高的效率，比第一部份提高了12%，並且與其他主體材料進行比較也是得到相對較高的元件效率，並且利用阻抗頻譜分析去證實載子確實有侷限住。

Currently, exciplex had drawn attention of its potential for efficient electroluminescence or for use as a host. In this study, we use TCTA and TmPyPB to form a exciplex host and FIrpic were used as dopant to emit blue phosphorescent light. We changed the mixed ratio of the host to improve the current efficiency of the device and used various types of data to analyze the most important factors affecting efficiency (such as photoluminescence, single carrier device, and electroluminescence). We found out the ratio 1:2 was the best ratio in this study. The device with mixed ratio 1:2 got higher current efficiency (56cd/A). In the second part, we changed the structure of the device to improve the current efficiency and change the thickness of the emission layer to investigate the carrier limitation ability. We found out the thickness of emission layer was 15nm had the better current efficiency because of its better carrier limitation ability.

[1] M. Pope, H. Kallmann, and P. Magnante, "Electroluminescence in organic crystals," The Journal of Chemical Physics, vol. 38, no. 8, pp. 2042-2043, 1963.
[2] H. Leonhardt and A. Weller, "Elektronenübertragungsreaktionen des angeregten Perylens," Berichte der Bunsengesellschaft für physikalische Chemie, vol. 67, no. 8, pp. 791-795, 1963.
[3] J.-S. Wu, J.-H. Zhou, P.-F. Wang, X.-H. Zhang, and S.-K. Wu, "New fluorescent chemosensor based on exciplex signaling mechanism," Organic Letters, vol. 7, no. 11, pp. 2133-2136, 2005.
[4] D. Wang et al., "Broad wavelength modulating and design of organic white diode based on lighting by using exciplex emission from mixed acceptors," Applied physics letters, vol. 89, no. 23, p. 233511, 2006.
[5] C.-H. Chang et al., "Efficient red, green, blue and white organic light-emitting diodes with same exciplex host," Japanese Journal of Applied Physics, vol. 55, no. 3S1, p. 03CD02, 2016.
[6] K. Goushi and C. Adachi, "Efficient organic light-emitting diodes through up-conversion from triplet to singlet excited states of exciplexes," Applied Physics Letters, vol. 101, no. 2, p. 023306, 2012.
[7] T. Zhang et al., "Efficient triplet application in exciplex delayed-fluorescence oleds using a reverse intersystem crossing mechanism based on a δ es–t of around zero," ACS applied materials & interfaces, vol. 6, no. 15, pp. 11907-11914, 2014.
[8] K. Goushi, K. Yoshida, K. Sato, and C. Adachi, "Organic light-emitting diodes employing efficient reverse intersystem crossing for triplet-to-singlet state conversion," Nature Photonics, vol. 6, no. 4, pp. 253-258, 2012.
[9] X. K. Liu et al., "Prediction and Design of Efficient Exciplex Emitters for High‐Efficiency, Thermally Activated Delayed‐Fluorescence Organic Light‐Emitting Diodes," Advanced Materials, vol. 27, no. 14, pp. 2378-2383, 2015.
[10] Y. Kuwabara, H. Ogawa, H. Inada, N. Noma, and Y. Shirota, "Thermally stable multilared organic electroluminescent devices using novel starburst molecules, 4, 4′, 4 ″‐Tri (N‐carbazolyl) triphenylamine (TCTA) and 4, 4′, 4 ″‐Tris (3‐methylphenylphenylamino) triphenylamine (m‐MTDATA), as hole‐transport materials," Advanced Materials, vol. 6, no. 9, pp. 677-679, 1994.
[11] S. J. Su, T. Chiba, T. Takeda, and J. Kido, "Pyridine‐containing triphenylbenzene derivatives with high electron mobility for highly efficient phosphorescent OLEDs," Advanced Materials, vol. 20, no. 11, pp. 2125-2130, 2008.
[12] J. Jiang, X. Lin, H. Lei, J. Li, and Z. Kou, "The effect of the exciplex heterojunction interlayer on efficiency roll-off in non-doped blue phosphorescent organic light-emitting diodes," Optical Materials, vol. 99, p. 109561, 2020.
[13] Y. S. Park, S. Lee, K. H. Kim, S. Y. Kim, J. H. Lee, and J. J. Kim, "Exciplex‐forming co‐host for organic light‐emitting diodes with ultimate efficiency," Advanced Functional Materials, vol. 23, no. 39, pp. 4914-4920, 2013.
[14] J. H. Lee et al., "An exciplex forming host for highly efficient blue organic light emitting diodes with low driving voltage," Advanced Functional Materials, vol. 25, no. 3, pp. 361-366, 2015.
[15] B. Yao, X. Lin, B. Zhang, H. Wang, X. Liu, and Z. Xie, "Power-efficient and solution-processed red phosphorescent organic light-emitting diodes by choosing combinations of small molecular materials to form a well-dispersed exciplex co-host," Journal of Materials Chemistry C, vol. 6, no. 16, pp. 4409-4417, 2018.
[16] Y. Seino, H. Sasabe, Y. J. Pu, and J. Kido, "High‐performance blue phosphorescent OLEDs using energy transfer from exciplex," Advanced Materials, vol. 26, no. 10, pp. 1612-1616, 2014.
[17] H. Skoog, "Nieman. Principles of instrumental analysis," Harcourt College Publishers, vol. 5, pp. 329-351, 1998.
[18] J. R. Lakowicz, "Introduction to fluorescence," in Principles of fluorescence spectroscopy: Springer, 1999, pp. 1-23.
[19] A. L. Burin and M. A. Ratner, "Exciton migration and cathode quenching in organic light emitting diodes," The Journal of Physical Chemistry A, vol. 104, no. 20, pp. 4704-4710, 2000.
[20] C. W. Tang and S. A. VanSlyke, "Organic electroluminescent diodes," Applied physics letters, vol. 51, no. 12, pp. 913-915, 1987.
[21] C. Adachi, S. Tokito, T. Tsutsui, and S. Saito, "Organic electroluminescent device with a three-layer structure," Japanese journal of applied physics, vol. 27, no. 4A, p. L713, 1988.
[22] S. R. Forrest, V. Bulovic, and P. Peumans, "Organic photosensitive optoelectronic device with an exciton blocking layer," ed: Google Patents, 2002.
[23] V. C. Bender, T. B. Marchesan, and J. M. Alonso, "Solid-state lighting: A concise review of the state of the art on LED and OLED modeling," IEEE Industrial Electronics Magazine, vol. 9, no. 2, pp. 6-16, 2015.
[24] M. Baldo, M. Thompson, and S. Forrest, "High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer," Nature, vol. 403, no. 6771, pp. 750-753, 2000.
[25] H. Tanaka, K. Shizu, H. Miyazaki, and C. Adachi, "Efficient green thermally activated delayed fluorescence (TADF) from a phenoxazine–triphenyltriazine (PXZ–TRZ) derivative," Chemical Communications, vol. 48, no. 93, pp. 11392-11394, 2012.
[26] S. J. Yeh et al., "New dopant and host materials for blue‐light‐emitting phosphorescent organic electroluminescent devices," Advanced Materials, vol. 17, no. 3, pp. 285-289, 2005.
[27] Q.-S. Tian, L. Zhang, Y. Hu, S. Yuan, Q. Wang, and L.-S. Liao, "High-performance white organic light-emitting diodes with simplified structure incorporating novel exciplex-forming host," ACS applied materials & interfaces, vol. 10, no. 45, pp. 39116-39123, 2018.