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研究生：	葉政瑋 Yeh, Cheng-Wei
論文名稱：	利用溶劑極性差異製作雙層高分子有機白光元件 Bilayer polymer white-light-emitting diodes utilizing the different polarity of solvents
指導教授：	蘇炎坤 Su, Yan-Kuin
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 微電子工程研究所 Institute of Microelectronics
論文出版年：	2007
畢業學年度：	95
語文別：	英文
論文頁數：	111
中文關鍵詞：	白光高分子二極體、溶劑極性差異
外文關鍵詞：	WPLED, different of polarity of solvents
相關次數：	點閱：52 下載：2
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由於資訊產業的發展，人們對顯示器的要求日漸增高，而顯示器的主流也由傳統低成本、畫質好但過於大、重的陰極射線管（CRT）顯示器，到現在漸漸普及化的具輕薄但有視角限制的液晶（Liquid crystal display，LCD）顯示器。然而，有機電激發光二極體（Organic light-emitting diodes，OLED）的出現，吸引了大家的目光，而其中以共軛高分子白光有機電激發光二極體（Polymer white-light-emitting diodes，WPLED）具有輕薄的特性並且沒有視角限制，且有著大面積、高亮度以及簡單且較為廉價的製程，成為大家最感興趣的有機元件之一。
我的研究主要是以雙發光層、以互補色混成白光的WPLED。雙發光層有著比單發光層更容易調配色光比例、色光穩定、高發光效率的特性，但是由於高分子製程是以溶液塗佈的方式來成長發光層，所以很容易在塗佈第二層時將第一層有機物再一次的溶解侵蝕而大大降低效率，於是這成為很多研究員欲解決問題。當然我也不例外，而我採用的方式是以溶液極性相溶原理來改善上述的問題。
首先，我以ITO/PEDOT:PSS/PVK+MEH-PPV/PFO/Ca/Al為雙發光層結構。在此PEDOT:PSS是當做電洞傳輸層；PFO、MEH-PPV分別為藍光、橘光的有機螢光材料，白光就是利用這兩種材料互相調配比例而混成的；而PVK在此扮演host、電洞傳輸層、電子阻擋層與能量轉移輸出者。
我將PVK+MEH-PPV混在氯苯（極性溶液）中，當作第一層發光層；將PFO溶入對-二甲苯（非極性溶液）中，當作第二層發光層。因此，可以藉由PVK是host且不溶於非極性溶液（在此為對-二甲苯）的特性，來達成使第一、第二發光層不互溶的目的，並且設有對照組來互相比較，證實我的方法可行。而在實驗當中，我先將PFO調配至效率與亮度最大值，後在改變MEH-PPV在PVK中的組成比例來產生白光。經幾度調配後，我得到最靠近純白光的CIE值為（0.307，0.342），且該元件的最大亮度可以到達5004 cd/m2 (7.9V)，且得到的最高效率值為1.65 cd/A (11.9V)。

By the development of the intelligent industry, people have more require for displays. First, cathode ray tube (CRT) displays are low-cost and good image quality but too big and too heavy. Then, liquid crystal displays (LCDs) are thinner and lighter than CRT displays but has narrow viewing angle. So, the appearance of organic light-emitting diodes (OLEDs) has attracted much attention. Among others, many people are interested in conjugated polymer white-light-emitting diodes (WPLEDs) because they are thin and light, and having wide viewing angle, easy process, low cost, high brightness, and large-area applications.
My study is about WPLEDs that are based on bilayer, and get white light by an additive mixture of the two complementary colors. The bilayer structure excels the single layer structure at the modulation of the blend ratio, color stability, and luminance efficiencies. But WPLEDs with bilayer structures are fabricated by the spin-coating method, the former emitting layer will be dissolved belike by the latter emitting layer that results in lower efficiencies. Many researchers want to solve this problem. In our research, we utilize the different of polarity of solvents to improve this appearance.
At first, the devices are made as ITO/PEDOT:PSS/PVK+MEH-PPV/ PFO/Ca/Al. PEDOT: PSS served as a hole-transporting layer (HTL). PFO and MEH-PPV serve as Blue and orange fluorescence materials separately. PVK serves as a host, a hole-transporting material, and a electron-blocking material, and can energy transfer to MEH-PPV.
In this work, PVK and MEH-PPV that dissolve in dichlorobenzene serve as the former emitting layer. Here dichlorobenzene is a polar solvent. PFO that dissolved in p-xylene serves as the latter emitting layer. Here p-xylene is a nonpolar solvent. Therefore, the former emitting layer should not dissolve in the latter emitting layer because PVK which serves as a host doesn’t dissolve in nonpolar solvents, and we then compare the device with other controls to confirm my assumption.
At last, we get a resultant device having a white emission of CIE (0.307, 0.342) has a maximum efficiency of 1.65cd/A at 7.9 V and a maximum brightness of 5004 cd/m2 at 11.9 V.

Content
Abstract ( in chinese )...................................I
Abstract ( in English ).................................III
Acknowledgement...........................................V
Content..................................................VI
Figure Captions..........................................IX
  Chapter 1 Introduction..................................1
    1-1 Historical development of Organic EL devices......1
    1-2 The advantages and disadvantages of OLEDs.........1
    1-3 OLEDs and PLEDs...................................4
      1-3-1 Small molecular organic light-emitting diodes.4
      1-3-2 Polymer light-emitting diodes.................5
    1-4 Full color OLED displays..........................6
      1-4-1 Three ways to achieve full color OLED displays6
      1-4-2 The applications and advantages of WOLEDs.....8
      1-4-3 An analysis of color in CIE..................11
  Chapter 2 Polymer light-emitting diodes................13
    2-1 The structure of PLEDs...........................13
      2-1-1 Anode........................................13
      2-1-2 Polymer layers...............................14
      2-1-3 Cathode......................................17
    2-2 Principles of operation mechanism of PLEDs.......18
      2-2-1 The emission mechanism.......................19
      2-2-2 Device efficiency............................21
    2-3 Degradation of organic light-emitting diodes.....27
    2-4 Way to polymer white-light-emitting diodes.......28
      2-4-1 Way to white light...........................28
      2-4-2 The emitting layer of WPLEDs.................29
    2-5 The aim of this research.........................33
  Chapter 3 Experimental procedures and systems..........35
    3-1 Preamble.........................................35
    3-2 Materials used in this experiment................36
      3-2-1 Anode, cathode, and polymer materials........36
      3-2-2 Solvent used in polymer layers of PLEDs......37
    3-3 Experimental procedures..........................39
      3-3-1 Substrate cleaning...........................39
      3-3-2 Fabrication of polymer layers and the cathode40
    3-4 Measurement systems..............................41
      3-4-1 Current vs. Voltage measurement..............41
      3-4-2 Optical Measurements.........................41
  Chapter 4 Results and discussions......................44
    4-1 Preamble.........................................44
    4-2 Part I: The analysis of basic devices............45
      4-2-1 Characteristics of pure PFO..................45
      4-2-2 Summary of part I............................47
    4-3 Part II: The method to enhance efficiency........47
      4-3-1 Characteristics of PVK/PFO...................47
      4-3-2 Discussion of part II........................51
      4-3-3 Summary of part II...........................52
    4-4 Part III: Bilayer PWLEDs.........................53
      4-4-1 Characteristics of bilayer WPLEDs............53
      4-4-2 Summary of part III..........................55
    4-5 Part IV: Comparing bilayer PWLED with others.....55
      4-5-1 Characteristics of other WPLEDs..............55
      4-5-2 Comparing with other WPLEDs..................58
      4-5-3 Summary of part IV...........................59
  Chapter 5 Conclusion...................................60
  Chapter 6 Future work..................................62
Reference................................................63

Table and figure Captions
Table 1-1 The comparison of OLEDs with other FPDs........68
Table 1-2 The comparison of OLEDs and PLEDs..............69
Fig.1-1(a) OLED：Thinner and Light weight................70
       (b) Flexibility substrate
Fig.1-2(a) A basic bilayer OLED..........................71
       (b) Energy diagram of a bilayer OLED
Fig.1-3(a) A basic multilayer structure of OLED..........72
       (b) Energy diagram of a multilayer OLED
Fig.1-4(a) A basic structure of PLED.....................73
       (b) The two ways of manufacturing PLEDs
         (I) Spin coating (II) Ink-jet printing
Fig.1-5 A complete multilayer structure of PLED..........74
Fig.1-6(a) Parallel trichromatic independent method......75
       (b) Color conversion method
       (c) Color filter method
Fig.1-7 The comparison of three ways to achieve full color 
        OLED displays....................................76
Fig.1-8 Förster energy transfer..........................77
Fig.1-9 Dexter energy transfer...........................78
Fig.1-10(a) Mechanism of excimers........................79
        (b) Mechanism of exciplexes
Fig.1-11 CIE chromaticity diagram........................80
Fig.2-1(a) A structure of PLED...........................81
       (b) The two ways of manufacturing PLEDs
         (I) Spin coating (II) Ink-jet printing
Fig.2-2 The manufacturing processes of PLEDs.............82
Fig.2-3 Basic emission mechanism of a PLED...............83
Fig.2-4(a) Singlet state and Triplet state...............84
       (b) Fluorescence emission mechanisms and     
           Phosphorescence emission mechanisms
Fig.2-5 Phase segregation................................85
Fig.2-6(a)Excitons quenching near the electrodes.........86
       (b)Way to improve excitons quenching
       (c)Recombination zone moves with voltage
Fig.3-1(a)The PL curve of PFO............................87
       (b)The PL curve of MEH-PPV
Fig.3-2(a) Structural formula of PFO.....................88
       (b) Structural formula of MEH-PPV
       (c) Structural formula of PVK
Fig.3-3(a) Good solvent..................................89
       (b) Θ solvent
       (c) Poor solvent
Fig.3-4(a) Structural formula of p-xylene................90
       (b) Structural formula of toluene
       (c) Structural formula of dichlorobenzene
Fig.4-1(a) The structure of Device I.....................91
       (b)The energy level graph of Device I
Fig.4-2(a)The I-V curves of Device I.....................92
       (b)The L-V curves of Device I
Fig.4-3 The E-I curves of Device I.......................93
Fig.4-4(a)The EL curves of Device I......................94
       (b)The CIE diagrams of Device I
Fig.4-5(a)The structure of Device II.....................95
       (b)The energy level graph of Device II
Fig.4-6(a)The I-V curves of Device II....................96
       (b)The L-V curves of Device II
Fig.4-7 The E-I curves of Device II......................97
Fig.4-8(a)The EL curves of Device II.....................98
       (b)The CIE diagrams of Device II
Fig.4-9(a)The structures of controls.....................99
       (b)The sketch maps of controls
Fig.4-10 The CIE diagrams and characteristics of 
         controls.......................................100
Fig.4-11(a)The structure of Device III..................101
        (b)The energy level graph of Device III
Fig.4-12(a)The I-V curves of Device III.................102
        (b)The L-V curves of Device III
Fig.4-13 The E-I curves of Device III...................103
Fig.4-14 The EL curves of Device III....................104
Fig.4-15 The CIE diagrams of Device III.................105
Fig.4-16(a)The structure of Device IV-A.................106
        (b)The structures of Device IV-A and Device IV-B
Fig.4-17(a)The I-V curves of Device (6), (8), (9), and (10)
         ...............................................107
        (b)The L-V curves of Device (6), (8), (9), and (10)
Fig.4-18 The E-I curves of Device (6), (8), (9), and (10)
         ...............................................108
Fig.4-19 The EL curves of Device (6), (8), (9), and (10)
         ...............................................109
Fig.4-20 The CIE diagrams of Device (6), (8), (9), and (10)
         ...............................................110
Fig.4-21 Alpha-Step test................................111
                                    

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校內：2012-07-02公開
校外：2017-07-02公開

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