近年來，有機發光二極體(Organic light-emitting diode，簡稱OLED)為新一代顯示器重要技術之一，具可饒性、高發光效率、廣視角、厚度輕薄以及反應時間短等優勢，因此受到了越來越多的關注，本論文以熱活化延遲螢光(TADF)材料為出發點，開發了高效率之綠色OLED以及高色純度之WOLED。
本論文主要包含兩大部分，第一部分利用界面Exciplex將激發態之能量有效轉移至綠光TADF客體材料，並且藉由避開PL量子效率低的材料組合、傳輸層厚度、客體摻雜濃度及客體摻雜位置等調整，並且通過Contact angle、PL、TRPL、吸收光譜、穿透度以及阻抗頻譜分析儀，分析摻雜濃度對元件的影響以及元件的能量轉移、載子堆積、傳輸特性，最終的綠色OLED實現了144cd/A的CEmax、126lm/W的PEmax與43.9 %的EQEmax，並且也有低的啟動電壓，不僅避免了磷光所帶來的重金屬汙染，另外也在綠色TADF OLED 達到了效率上的突破，
第二部分則是基於第一部分的綠色TADF OLED，額外摻雜紅色磷光材料於mCP，以Exciplex的藍光與紅、綠色之客體材料作為三原色之基底，並且透過結構調整、客體摻雜濃度調整以及傳輸層厚度進行元件優化，最終獲得的WOLED實現了34.4cd/A的CEmax、36.1lm/W的PEmax、20.8 %的EQEmax與81的CRI，不僅達到了高顯色指數，也維持了不錯的元件效率。

This work is divided into two main parts. In the first part, the energy of the excited state is effectively transferred to the green TADF guest material using an interface exciplex. By avoiding material combinations with low photoluminescence (PL) quantum efficiency, and optimizing the thickness of the transport layers, guest doping concentration, and guest doping positions. The resulting green OLED achieved a maximum current efficiency (CEmax) of 144 cd/A, a maximum power efficiency (PEmax) of 126 lm/W, and a maximum external quantum efficiency (EQEmax) of 43.9%, alongside a low turn-on voltage. The second part of this study builds upon the green TADF OLED developed in the first part, with additional doping of red phosphorescent material into mCP. By utilizing blue Exciplex along with red and green guest materials as the basis for the three primary colors, and through adjustments in structure, device optimization was achieved. The resulting WOLED demonstrated a CEmax of 34.4 cd/A, a PEmax of 36.1 lm/W, an EQEmax of 20.8%, and a CRI of 81.

[1] M. Koden, OLED displays and lighting. John Wiley & Sons, 2016.
[2] G. Hong et al., "A brief history of OLEDs—emitter development and industry milestones," Advanced Materials, vol. 33, no. 9, p. 2005630, 2021.
[3] A. Endo, M. Ogasawara, A. Takahashi, D. Yokoyama, Y. Kato, and C. Adachi, "Thermally activated delayed fluorescence from Sn4+-porphyrin complexes and their application to organic light-emitting diodes-A novel mechanism for electroluminescence," Advanced Materials, vol. 21, no. 47, pp. 4802-4806, 2009.
[4] J. X. Wang et al., "Time‐dependent afterglow color in a single‐component organic molecular crystal," Angewandte Chemie, vol. 132, no. 25, pp. 10118-10122, 2020.
[5] J. Li et al., "A Significantly Twisted Spirocyclic Phosphine Oxide as a Universal Host for High‐Efficiency Full‐Color Thermally Activated Delayed Fluorescence Diodes," Advanced Materials, vol. 28, no. 16, pp. 3122-3130, 2016.
[6] Y. Liu, C. Li, Z. Ren, S. Yan, and M. R. Bryce, "All-organic thermally activated delayed fluorescence materials for organic light-emitting diodes," Nature Reviews Materials, vol. 3, no. 4, pp. 1-20, 2018.
[7] S. Hirata et al., "Highly efficient blue electroluminescence based on thermally activated delayed fluorescence," Nature materials, vol. 14, no. 3, pp. 330-336, 2015.
[8] A. Endo et al., "Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes," Applied Physics Letters, vol. 98, no. 8, 2011.
[9] J. Li, Q. Zhang, H. Nomura, H. Miyazaki, and C. Adachi, "Thermally activated delayed fluorescence from 3nπ* to 1nπ* up-conversion and its application to organic light-emitting diodes," Applied Physics Letters, vol. 105, no. 1, 2014.
[10] H. Uoyama, K. Goushi, K. Shizu, H. Nomura, and C. Adachi, "Highly efficient organic light-emitting diodes from delayed fluorescence," Nature, vol. 492, no. 7428, pp. 234-238, 2012.
[11] Z. Wang, C. Wang, H. Zhang, Z. Liu, B. Zhao, and W. Li, "The application of charge transfer host based exciplex and thermally activated delayed fluorescence materials in organic light-emitting diodes," Organic Electronics, vol. 66, pp. 227-241, 2019.
[12] K.-Y. Lu et al., "Wide-range color tuning of iridium biscarbene complexes from blue to red by different N⁁ N ligands: an alternative route for adjusting the emission colors," Advanced materials (Deerfield Beach, Fla.), vol. 23, no. 42, pp. 4933-4937, 2011.
[13] L. Xiao et al., "Recent progresses on materials for electrophosphorescent organic light‐emitting devices," Advanced Materials, vol. 23, no. 8, pp. 926-952, 2011.
[14] C. Ulbricht, B. Beyer, C. Friebe, A. Winter, and U. S. Schubert, "Recent developments in the application of phosphorescent iridium (III) complex systems," Advanced Materials, vol. 21, no. 44, pp. 4418-4441, 2009.
[15] M. Baldo, S. Lamansky, P. Burrows, M. Thompson, and S. Forrest, "Very high-efficiency green organic light-emitting devices based on electrophosphorescence," Applied Physics Letters, vol. 75, no. 1, pp. 4-6, 1999.
[16] C. Adachi, M. A. Baldo, M. E. Thompson, and S. R. Forrest, "Nearly 100% internal phosphorescence efficiency in an organic light-emitting device," Journal of Applied Physics, vol. 90, no. 10, pp. 5048-5051, 2001.
[17] M. A. Baldo et al., "Highly efficient phosphorescent emission from organic electroluminescent devices," in Electrophosphorescent Materials and Devices: Jenny Stanford Publishing, 2023, pp. 1-11.
[18] B. S. Kim and J. Y. Lee, "Engineering of mixed host for high external quantum efficiency above 25% in green thermally activated delayed fluorescence device," Advanced functional materials, vol. 24, no. 25, pp. 3970-3977, 2014.
[19] M. P. Gaj, C. Fuentes-Hernandez, Y. Zhang, S. R. Marder, and B. Kippelen, "Highly efficient organic light-emitting diodes from thermally activated delayed fluorescence using a sulfone–carbazole host material," Organic Electronics, vol. 16, pp. 109-112, 2015.
[20] Y. Seino, S. Inomata, H. Sasabe, Y. J. Pu, and J. Kido, "High‐performance green OLEDs using thermally activated delayed fluorescence with a power efficiency of over 100 lm W− 1," Advanced Materials, vol. 28, no. 13, pp. 2638-2643, 2016.
[21] W. Liu, R. Cui, L. Zhou, Y. Cui, Q. Zhu, and L. Y. Jin, "Efficient green organic electroluminescent devices based on thermally activated delayed fluorescence emitter by constructing supplementary light-emitting layer," Thin Solid Films, vol. 685, pp. 353-359, 2019.
[22] T.-C. Yeh, J.-D. Lee, L.-Y. Chen, T. Chatterjee, W.-Y. Hung, and K.-T. Wong, "New naphthyridine-based bipolar host materials for thermally activated delayed fluorescent organic light-emitting diodes," Organic Electronics, vol. 70, pp. 55-62, 2019.
[23] Y. Zheng et al., "Investigation of bipolar matrix based mixed host in highly efficient green delayed fluorescence organic light-emitting diodes," Current Applied Physics, vol. 22, pp. 30-35, 2021.
[24] Y. J. Cho, K. S. Yook, and J. Y. Lee, "A universal host material for high external quantum efficiency close to 25% and long lifetime in green fluorescent and phosphorescent OLEDs," Advanced Materials (Deerfield Beach, Fla.), vol. 26, no. 24, pp. 4050-4055, 2014.
[25] B. Dong et al., "High luminance/efficiency monochrome and white organic light emitting diodes based pure exciplex emission," Organic electronics, vol. 106, p. 106528, 2022.
[26] K. Ivaniuk et al., "Contribution Of Fluorescence And Exciplex Emission Into Efficient White OLED," in 2020 IEEE 15th International Conference on Advanced Trends in Radioelectronics, Telecommunications and Computer Engineering (TCSET), 2020: IEEE, pp. 821-824.
[27] Z. Wu et al., "High‐Performance Hybrid White Organic Light‐Emitting Diodes with Superior Efficiency/Color Rendering Index/Color Stability and Low Efficiency Roll‐Off Based on a Blue Thermally Activated Delayed Fluorescent Emitter," Advanced Functional Materials, vol. 26, no. 19, pp. 3306-3313, 2016.
[28] D. Feng, D. Dong, L. Lian, H. Wang, and G. He, "High efficiency non-doped white organic light-emitting diodes based on blue exciplex emission," Organic Electronics, vol. 56, pp. 216-220, 2018.
[29] Z. He et al., "Blue and white solution-processed TADF-OLEDs with over 20% EQE, low driving voltages and moderate efficiency decrease based on interfacial exciplex hosts," Journal of Materials Chemistry C, vol. 7, no. 38, pp. 11806-11812, 2019.
[30] Q. Ren, Y. Zhao, and H. Wang, "A low cost and simple structured WOLED device based on exciplex host and full fluorescent materials," Solid-State Electronics, vol. 208, p. 108753, 2023.
[31] T. Nakamura et al., "Highly efficient and stable green fluorescent OLEDs with high color purity using a BODIPY derivative," Molecular Systems Design & Engineering, vol. 8, no. 7, pp. 866-873, 2023.
[32] Y. Miao et al., "Simplified phosphorescent organic light-emitting devices using heavy doping with an Ir complex as an emitter," RSC advances, vol. 5, no. 6, pp. 4261-4265, 2015.
[33] R. Grover, R. Srivastava, M. Kamalasanan, and D. Mehta, "Novel organic electron injection layer for efficient and stable organic light emitting diodes," Journal of luminescence, vol. 146, pp. 53-56, 2014.
[34] C.-T. Tsai, Y.-H. Liu, J.-F. Tang, P.-C. Kao, C.-H. Chiang, and S.-Y. Chu, "Effects of novel transition metal oxide doped bilayer structure on hole injection and transport characteristics for organic light-emitting diodes," Synthetic Metals, vol. 243, pp. 121-126, 2018.
[35] 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.
[36] M. Eck, "Performance enhancement of hybrid nanocrystal-polymer bulk heterojunction solar cells:: aspects of device efficiency, reproducibility, and stability," Dissertation, Albert-Ludwigs-Universität Freiburg, 2014, 2014.
[37] Y. Sun and S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded low-index grids," Nature photonics, vol. 2, no. 8, pp. 483-487, 2008.
[38] B. R. Masters, "Molecular fluorescence: principles and applications," ed: Society of Photo-Optical Instrumentation Engineers, 2013.
[39] M. Zhang, C.-J. Zheng, H. Lin, and S.-L. Tao, "Thermally activated delayed fluorescence exciplex emitters for high-performance organic light-emitting diodes," Materials Horizons, vol. 8, no. 2, pp. 401-425, 2021.
[40] S. F. Wu et al., "White Organic LED with a Luminous Efficacy Exceeding 100 lm W− 1 without Light Out‐Coupling Enhancement Techniques," Advanced Functional Materials, vol. 27, no. 31, p. 1701314, 2017.
[41] P. Yuan, X. Qiao, D. Yan, and D. Ma, "Magnetic field effects on the quenching of triplet excitons in exciplex-based organic light emitting diodes," Journal of Materials Chemistry C, vol. 6, no. 21, pp. 5721-5726, 2018.
[42] X. Zhao, X. Tang, R. Pan, J. Xu, F. Qu, and Z. Xiong, "Direct observation of reverse intersystem crossing from fully confined triplet exciplexes using magneto-electroluminescence," Journal of Materials Chemistry C, vol. 7, no. 35, pp. 10841-10850, 2019.
[43] S. K. Cushing et al., "Excitation wavelength dependent fluorescence of graphene oxide controlled by strain," Nanoscale, vol. 9, no. 6, pp. 2240-2245, 2017.
[44] D. Graves, V. Jankus, F. B. Dias, and A. Monkman, "Photophysical Investigation of the Thermally Activated Delayed Emission from Films of m‐MTDATA: PBD Exciplex," Advanced Functional Materials, vol. 24, no. 16, pp. 2343-2351, 2014.
[45] C.-K. Moon, J.-S. Huh, J.-M. Kim, and J.-J. Kim, "Electronic structure and emission process of excited charge transfer states in solids," Chemistry of Materials, vol. 30, no. 16, pp. 5648-5654, 2018.
[46] P. Deotare et al., "Nanoscale transport of charge-transfer states in organic donor–acceptor blends," Nature materials, vol. 14, no. 11, pp. 1130-1134, 2015.
[47] B. Li et al., "An Effective Strategy toward High‐Efficiency Fluorescent OLEDs by Radiative Coupling of Spatially Separated Electron–Hole Pairs," Advanced Materials Interfaces, vol. 5, no. 10, p. 1800025, 2018.
[48] H. Mu, Y. Jiang, and H. Xie, "Efficient blue phosphorescent organic light emitting diodes based on exciplex and ultrathin Firpic sandwiched layer," Organic Electronics, vol. 66, pp. 195-205, 2019.
[49] H. Nakanotani, T. Furukawa, K. Morimoto, and C. Adachi, "Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers," Science Advances, vol. 2, no. 2, p. e1501470, 2016.
[50] 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.
[51] 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.
[52] 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, 2012.
[53] M. Kiy, I. Biaggio, M. Koehler, and P. Günter, "Conditions for ohmic electron injection at the Mg/Alq 3 interface," Applied physics letters, vol. 80, no. 23, pp. 4366-4368, 2002.
[54] S. Barth et al., "Current injection from a metal to a disordered hopping system. III. Comparison between experiment and Monte Carlo simulation," Physical Review B, vol. 60, no. 12, p. 8791, 1999.
[55] M. A. Lampert and R. B. Schilling, "Current injection in solids: The regional approximation method," in Semiconductors and semimetals, vol. 6: Elsevier, 1970, pp. 1-96.
[56] T. Tsutsui, M. Yahiro, H. Yokogawa, K. Kawano, and M. Yokoyama, "Doubling coupling‐out efficiency in organic light‐emitting devices using a thin silica aerogel layer," Advanced Materials, vol. 13, no. 15, pp. 1149-1152, 2001.
[57] S. Reineke, K. Walzer, and K. Leo, "Triplet-exciton quenching in organic phosphorescent light-emitting diodes with Ir-based emitters," Physical Review B, vol. 75, no. 12, p. 125328, 2007.
[58] J. Kim, T. Lee, J. Kwak, and C. Lee, "Photovoltaic characterizing method of degradation of polymer light-emitting diodes based on ideality factor and density of states," Applied Physics Letters, vol. 119, no. 12, 2021.
[59] H. Nakanotani, K. Masui, J. Nishide, T. Shibata, and C. Adachi, "Promising operational stability of high-efficiency organic light-emitting diodes based on thermally activated delayed fluorescence," Scientific reports, vol. 3, no. 1, p. 2127, 2013.
[60] Y. Zhao et al., "All-fluorescent white organic light-emitting diodes with EQE exceeding theoretical limit of 5% by incorporating a novel yellow fluorophor in co-doping forming blue exciplex," Organic Electronics, vol. 83, p. 105746, 2020.
[61] Y. Miao, G. Wang, M. Yin, Y. Guo, B. Zhao, and H. Wang, "Phosphorescent ultrathin emitting layers sensitized by TADF interfacial exciplex enables simple and efficient monochrome/white organic light-emitting diodes," Chemical Engineering Journal, vol. 461, p. 141921, 2023.
[62] M. Wu, Z. Wang, Y. Liu, Y. Qi, and J. Yu, "Non-doped phosphorescent organic light-emitting devices with an exciplex forming planar structure for efficiency enhancement," Dyes and Pigments, vol. 164, pp. 119-125, 2019.
[63] S. Tsang, S. So, and J. Xu, "Application of admittance spectroscopy to evaluate carrier mobility in organic charge transport materials," Journal of applied physics, vol. 99, no. 1, 2006.
[64] H. Park et al., "Admittance spectroscopic analysis of organic light emitting diodes with the CFX plasma treatment on the surface of indium tin oxide anodes," Thin Solid Films, vol. 516, no. 7, pp. 1370-1373, 2008.
[65] H. Wang et al., "High Efficiency Non‐Doped White Organic Light Emitting Diodes Based on a Bilayer Interface‐Exciplex Structure," physica status solidi (a), vol. 216, no. 11, p. 1900034, 2019.