臺灣博碩士論文加值系統

近年來，科技追求愈輕愈薄的產品，利用軟性基板替代玻璃基板更是許多產品追求的目標。有機發光二極體(OLED)是可撓曲的元件，卻因為電極使用易碎的氧化物材料而有所限制，因此發展一適用於軟性基板的電極是必要的。適當比例的銦鋅氧化物(IZO)在室溫下是一種非結晶態(amorphous)，與膜層之間有較小的應力，與最常使用的銦錫氧化物(ITO)相比可以有更大的彎曲程度。將IZO與ITO分別沉積於OLED陰極做特性上比較，IZO陰極元件有較低的驅動電壓及較高的元件亮度，並且將IZO陰極做不同厚度的比較，不只會受到電性上的影響，亦會受到物理光學的影響而有不同的變化。
發展更輕更薄的產品最重要的是改變傳統的玻璃封裝方式，而以薄膜封裝是其最佳的選擇。在許多薄膜沉積法中，原子層沉積法(ALD)是可以讓無機膜幾乎無孔洞的沉積方式，因而達到很高程度的阻氣阻水效果，其中氧化鋁(Al2O3)是最常使用ALD沉積的阻障膜材料，然而其在飽和水氣下易被水解，因此加入氧化鉿(HfO2)發展了疊層結構(Al2O3/ HfO2)作為薄膜封裝層。在ALD沉積過程必須使用到水氣，對於OLED是有可能造成損壞的來源，但經由實驗結果證明整個薄膜沉積過程皆不會對元件造成傷害，作為薄膜封裝的沉積是非常適合的。

There is an aim of the products is thinner and lighter weight, and replacing the substrate with a plastic substrate that can increase the number of OLED applications. In the OLEDs, the TCO of the electrode is the only brittle device layer that limited the development of the flexible OLED. The amorphous IZO thin film is investigated to use in OLED and it has a potential in flexible device. Moreover, the IZO cathode OLED had better properties than the ITO cathode OLED such as lower turn-on voltage and higher brightness. Besides, the optical characteristics were investigated in different thickness due to it not only affected by the electron and hole recombination but also varied from the physical optics.
Change the glass-lid encapsulation to the thin film passivation is also a point in the future. Atomic layer deposition (ALD) is one of deposition method of the thin film barrier and it could deposit a pinhole-free film to block the moisture and oxygen. Al2O3 is accepted as one of the most widely studied materials grown by ALD, but its hydrolyzed property could not extend the lifetime very well. Therefore, laminated Al2O3/HfO2 was developed as the thin film barrier. In the ALD process, the H2O precursor may injure the OLEDs, and there is no damage after the experiment confirmed. Consequently, the thin film barrier deposited by ALD method is very suitable.

Contents

指導教授推薦書………………….............………………………………
口試委員會審定書…………………….......………………………………
授權書….………………………………………….…………………….iii
致謝..…………………….………………………………………...…….iv
中文摘要………………………..………………............….……………..v
Abstract….……………………...……………………………..…………vi
Contents.………………………………………………………..……….vii
Chapter I Introduction..………………………….…………………...1
1-1 History of organic light-emitting diodes..……….……………….1
1-2 Structure of organic light-emitting diodes..…………...…………2
1-2-1 Mechanism of organic light-emitting diodes..…...………...2
1-2-2 The electrodes in OLEDs.…………………….……………3
1-3 Encapsulations of organic light-emitting diodes..……..………...5
1-3-1 The importance of encapsulation.……..….………………..5
1-3-2 Thin film barrier..…………………………...…...…………5
1-4 Flexible organic light-emitting diodes..……….…………………7
Chapter II Experimental and Measurement…………….…………13
2-1 Fabrication of polymer organic light-emitting device…..……..13
2-1-1 Materials..……………………...……………….…………13
2-1-2 Procedure of devices..…………………….………………14
2-2 Atomic layer deposition.……………………………………….15
2-3 Measurement..…………...………………….…………………16
Chapter III The TOLED with IZO cathode.……………………….20
3-1 The properties of IZO thin films..………………...……………20
3-1-1 Investigate the IZO thin films by papers..……….………..20
3-1-2 Investigate the IZO thin films by ourselves.……………...22
3-2 Organic light-emitting device with IZO electrode..……….......23
Chapter IV Encapsulation the TOLED by thin film barriers….…40
4-1Look into the thin film barriers..……………………………….40
4-2 Encapsulation the TOLED.……………………..……………43
4-2-1 The properties of the thin film barriers..………...………..43
4-2-2 Fabricate the thin film barriers on TOLED…..…...............44
Chapter V Conclusions and future work..………………………….52
References.……………………………………….………….………..54


Figure of Contents

Chapter I Introduction..………………………….…………………...1
Fig. 1-1 The basic structure of the organic light-emitting diode…………9
Fig. 1-2 The schematic of the theorem of the organic light-emitting…….9
Fig. 1-3(a) The improvement structure of the organic light-emitting diode, (b) The schematic of the improvement theorem of the organic light-emitting diode……………………………….……………..10
Fig. 1-4 The increase in resistance for ITO-coated PET versue the bending cycles…………………………………………………12
Fig. 1-5 Normalized resistance change after repeated bending as a function of the number of cycles for a-IZO/PC substrate........….12
Chapter II Experimental and Measurement…………….…………13
Fig. 2-1 The spectrum of the normalized PL of PFO material…………..18
Fig. 2-2 The flow chart of the procedure of the PLED………………….18
Fig. 2-3 The structure of the polymer OLED……………………………19
Fig. 2-4 The passivation polymer OLED with ZnO buffer layer (left) and without ZnO buffer layer (right)……………………………….19
Chapter III The TOLED with IZO cathode.……………………….20
Fig. 3-1 The resistivity of the IZO film in different working pressure….27
Fig. 3-2 The XRD of IZO thin film with different deposited substrate temperature…………………………………………………….27
Fig. 3-3 The AFM result in IZO thin film deposited in room temperature with 5mTorr shows Rrms = 0.719nm…………………………...28
Fig. 3-4 The resistivity of IZO and ITO films varied with substrate temperature…………………………………………………….28
Fig. 3-5(a) Compared the linear current density in various voltages with the OLED used ITO cathode and IZO cathode; the inset captured the voltage from 5.6V to 10V, and (b) Compared the logarithm current density in various voltage with the OLED used ITO cathode and IZO cathode………………………………………..30
Fig. 3-6 Compared the brightness with the OLED used ITO cathode and IZO cathode……………………………………………………31
Fig. 3-7 The transmittance of the IZO thin films in different thickness...32
Fig. 3-8 The optical simulation result in maximum intensity with different IZO cathode thickness and compared with the ITO cathode..…33
Fig. 3-9 The intensity of the OLED with different IZO cathode thickness that compared simulation results with experiment results……..33
Fig. 3-10 Top emitting and bottom emitting with 60nm IZO cathode in varied angle…………………………………………………….34
Fig. 3-11 Top emitting and bottom emitting with 80nm IZO cathode in varied angle…………………………………………………….34
Fig. 3-12 Top emitting and bottom emitting with 100nm IZO cathode in varied angle…………………………………………………….35
Fig. 3-13 Top emitting and bottom emitting with 120nm IZO cathode in varied angle…………………………………………………….35
Fig. 3-14(a) The spectrum of top emitting OLED with 60nm IZO cathode in varied angle, and (b) The spectrum of bottom emitting OLED with 60nm IZO cathode in varied angle…………….…………36
Fig. 3-15(a) The spectrum of top emitting OLED with 80nm IZO cathode in varied angle, and (b) The spectrum of bottom emitting OLED with 80nm IZO cathode in varied angle ………………………37
Fig. 3-16(a) The spectrum of top emitting OLED with 100nm IZO cathode in varied angle, and (b) The spectrum of bottom emitting OLED with 100nm IZO cathode in varied angle.…………….. 38
Fig. 3-17(a) The spectrum of top emitting OLED with 120nm IZO cathode in varied angle, and (b) The spectrum of bottom emitting OLED with 120nm IZO cathode in varied angle…….……….. 39
Chapter IV Encapsulation the TOLED by thin film barriers….…40
Fig. 4-1 The transmittance of single Al2O3, HfO2, and laminated Al2O3/HfO2 films grown by ALD……………………………...46
Fig. 4-2 The transmittance of the ZnO buffer layer grown by sputting…46
Fig. 4-3(a) Compared the linear current density in various voltages with the different encapsulation of the OLEDs and with a ZnO buffer layer, and (b) Compared the logarithm current density in various voltages with the different encapsulation of the OLEDs and with a ZnO buffer……………………………………………………47
Fig. 4-4 Compared the brightness with the different encapsulation of the OLEDs and with a ZnO buffer layer…………………………..48
Fig. 4-5 The photos of the OLED emitting with (a) glass-lid encapsulation , (b) Al2O3 passivation, and (c) laminated Al2O3/HfO2 that applied 12V…………………………………..49
Fig. 4-6(a) Compared the linear current density in various voltages with the different encapsulation of the OLEDs that without ZnO buffer layer, and (b) Compared the logarithm current density in various voltages with the different encapsulation of the OLEDs that without ZnO buffer layer………………………………… 50
Fig. 4-7 Compared the luminance with the different encapsulation of the OLEDs that without ZnO buffer layer…………………………51


Table of Contents

Chapter I Introduction..………………………….…………………...1
Table 1-1 WVTR and OTR for various polymers and coatings………11
Chapter III The TOLED with IZO cathode.……………………….20
Table 3-1 Definitions on the terminology of surface roughness………...26
Table 3-2 The work function of IZO, ITO, and commercial ITO……….29

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