溶液製程的刮刀塗佈法製作SimCP2、26DCzPPy、TCTA、TPCPF和SPPO13小分子材料為主發光體的多層磷光有機發光二極體。刮刀塗佈使得發光層擁有0.2 奈米的表面粗糙度並未有主客發光體的相分離現象。OXD-7被摻入進發光層提高傳輸電子能力，使得其中的26DCzPPy和SimCP2擁有較佳的電子電洞平衡，進而有較高的效率。在SimCP2中，藍光元件效率有15.8 cd/A，白光有24.2 cd/A。在相同元件結構下，不同主發光體在刮刀塗佈製程和蒸鍍製程有不同的元件效率。刮刀塗佈也成功地被驗證在多層結構與無銦錫氧化物基板的大面積上發光有機發光二極體。上發光有機發光二極體的半透明陰極是由氟化鋰、鋁和銀所構成。3奈米厚鋁和10奈米厚銀的組合擁有56%的穿透度和11Ω/sq的片電阻。這組合被應用在發光面積2公分乘於2.5公分的綠光磷光元件。其最高電流效率為25.2 cd/A並有差異小於10%的發光均勻度。此大面積上發光有機發光二極體具有與發光面積2公厘乘於2公厘的相同結構元件無異的電流效率且優於傳統的大面積下發光元件。氟化銫和n型摻雜電子傳輸層被應用於增進電子注入。在電壓6伏特下，亮度分別從141 cd/m2提升至502 cd/m2和304 cd/m2。刮刀塗佈在串接式白光有機發光二極體上有初步的成果。底層發光單元結晶化可藉由塗佈難以溶解之材料在連接層上。PEDOT:PSS具有低溶解性，可有效保護底部結構減少結晶化。TAZ取代在高溫退火會結晶的TPBi也可以減少結晶化。但旋轉塗佈PEDOT:PSS時，還是會溶解底部結構減少發光量。利用快乾的優點，刮刀塗佈PEDOT:PSS減少溶解。元件發光效率為5.8 cd/A，CIE座標為(0.36,0.41)，色溫為4735 K。

Solution-processable blade coating is applied to multi-layer phosphorescent organic light-emitting diodes (OLEDs) with five small-molecule hosts for the emission layer, including bis[3,5-di (9H-carbazol-9-yl)phenyl]diphenylsilane (SimCP2), 2,6-bis(3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy), 4,4’,4”-tris
-(N-carbazolyl)-triphenylamine (TCTA), 9,9-bis[4-(3,6-di-tert-butylcarbazol-9-yl)
phenyl]fluorine (TBCPF), and 2,7-bis(diphenylphosphoryl)-9,9’-spirobi[fluorene] (SPPO13). In general, blade coating gives low surface roughness of around 0.2 nm without phase separation of the emitter and the host. 1,3-Bis[2-(4-tert-butylphenyl)-
1,3,4-oxadiazo-5-yl]benzene (OXD-7) is added to tune the electron transport. Among all the hosts, 26DCzPPy and SimCP2 have by far the best electron–hole balance and consequently they show the highest efficiency. For SimCP2, the maximal efficiency is 15.8 cd/A for blue emission and 24.2 cd/A for white emission. The efficiencies for the hosts is found to be quite different from the efficiencies in vacuum evaporation for the same device structures. Large-area top-emitting OLEDs (TEOLEDs) with multi-layer structure are successfully demonstrated using blade coating on ITO-free substrate. The semitransparent cathode of TEOLED is composed of lithium fluoride (LiF), aluminum (Al) and silver (Ag). The composition of 3 nm Al and 10 nm Ag has a transmittance of 56% and a sheet resistance of 11 Ω/□. It is applied to the green phosphorescence device with an emissive area of 2 cm by 2.5 cm. The maximum current efficiency is 25.2 cd/A with high light-emission uniformity within 10% variation. The large-area TEOLEDs show comparable current efficiency as the small-area devices with an emissive area of 2 mm by 2 mm (having the same device structure) and better efficiency than traditional large-area bottom-emitting devices. Cesium fluoride (CsF) and n-doped electron transport layer are applied to improve electron injection. At 6 V, the luminance is raised from 141 cd/m2 to 502 cd/m2 and 304 cd/m2, respectively. Tandem WOLED is initially fabricated by blade coating process. The crystallization in bottom EL unit is reduced by coating low solubility material on the connecting layer. PEDOT:PSS has low solubility, so it efficiently protects bottom structure from crystallization. TAZ replaces TPBi which easily crystallizes in high temperature as ETL, thus the crystallization is solved. However, the bottom EL unit is dissolved during spin-coating PEDOT:PSS, so the luminance of bottom EL unit is weak. Blade-coated PEDOT:PSS shows reduced dissolution because of the advantage of rapid drying. Finally, the current efficiency is 5.8 cd/A; the CIE coordinates is (0.36,0.41); the color temperature is 4735 K.

Contents
中文摘要 i
Abstract ii
Contents iv
List of Figures v
List of Tables ix
Acknowledgement x
Chapter 1 Introduction 1
1-1 Background 1
1-2 History of OLED 2
1-3 Principles of OLED 3
1-3-1 Charge transport mechanisms 3
1-3-2 Metal contact and carrier injection limit 3
1-3-2-1 Schottky contact 4
1-3-2-2 Ohmic contact 4
1-3-2-3 Space-charge limited current, SCLC 5
1-3-2-4 Injection-limited current 6
1-3-3 Fluorescence and phosphorescence 7
1-3-4 Energy transfer 9
1-3-4-1 Radiative energy transfer 9
1-3-4-2 Non-radiative energy transfer 10
1-3-5 Device structure and working principle of OLED 12
1-4 Structure of the thesis 13
Chapter 2 Process of blade coating and measurements 15
2-1 Blade coating method 15
2-1-1 Benefits of blade coating 15
2-1-2 Process of blade coating 16
2-2 Measurements 19
Chapter 3 General application of blade coating to small-molecule hosts for OLED 20
3-1 Introduction and motivation 20
3-2 Fabricating process 22
3-3 Blue devices and film uniformity 26
3-4 Electron-hole balance 31
3-5 White OLED 34
3-6 Comparison with vacuum evaporation 39
3-7 Conclusion 43
Chapter 4 ITO-free large-area top-emission OLED 44
4-1 Introduction and motivation 44
4-2 Fabricating process 45
4-3 Semitransparent cathodes and green devices 48
4-4 Comparison of small-area and bottom-emitting devices 52
4-5 Improved cathode and n-doped electron transport layer 56
4-6 Conclusion 59
Chapter 5 White tandem OLED 60
5-1 Introduction and motivation 60
5-2 Fabrication process 61
5-3 Dissolution and crystallization 64
5-4 Adding protective PEDOT:PSS layer 65
5-5 Conclusion 71
Chapter 6 Conclusion 73
References 74
PUBLICATION LIST 79

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