臺灣博碩士論文加值系統

摘要
本研究以Wittig聚縮合法，製備主鏈上包含噁唑之聚合物2,5-di-phenyl-1,3,4-oxadiazole-4-diylvinylene-alt-3,6-triphenyl-amine-vinylene (POX-TPA)，並利用FT-IR及1H-NMR鑑定其結構，UV及PL光譜分析光學性質，OM及AFM觀察表面型態，CV量測氧化還原電位。固態POX-TPA之PL光譜最大放射波長(λmax)位於501 nm為一黃綠光材質，當其溶於不同極性溶劑之中，隨著溶劑極性升高，PL紅位移愈大，半幅寬愈寬。將POX-TPA製備成單層發光元件(ITO/POX-TPA(595 Å)/Al)，於操作電壓10伏特下，元件的最大亮度為32 cd/m2，發光效率達0.008 cd/A. 以含有N-methyl carbazole基團之芳香族polyamide-imide作為電洞傳遞層，雙層元件最大亮度由單層元件(ITO/POX-TPA(812 Å)/Al)的18 cd/m2提高至29 cd/m2，其發光效率達0.022 cd/A為單層元件的2.75倍。經氧電漿處理過之ITO，在9.5 V之下其單層元件(ITO (O2 plasma)/POX-TPA(812 Å)/Al)之最大亮度達55 cd/m2，發光效率0.014 cd/A。

ABSTRACT
Studies on the characteristics of 2,5-diphenyl-1,3,4-oxadiazole -4-diylvinylene-alt-3,6-triphenylamine-vinylene (POX-TPA), which contains oxadiazole groups in main chain is synthesized chemically by Wittig condensation route is to be carried out. The POX-TPA was characterized with identifying structure by FT-IR and 1H-NMR, analyzing the optical properties by UV-Vis and PL spectroscopy, observing morphology of surface by OM and AFM, and measuring potential of oxidation and reduction by CV. The PL spectrum of POX-TPA solid film exhibits a maximum peak at 501 nm, which corresponding to yellow-green light. The emission spectra of POX-TPA red shifted and the fluorescence halfwidth increased with increasing the polarity of solvents. Single-layer light-emitting-diode (LED) with the configuration of ITO/POX-TPA(595 Å)/Al shows the maximum brightness of 32 cd/m2 at a voltage of 10 V and photometric efficiency of 0.008 cd/A. As for double-layer LED with the configuration of ITO/polyamide-imide/POX-TPA(812 Å)/Al using aromatic polyamide-imide, which contains N-methyl-carbazole basic group, as a hole transport layer exhibit a maximum brightness from 18 (single-layer LED) to 29 cd/m2 and photometric efficiency of 0.022 cd/A, which is 2.75 times that of single-layer device ITO/POX-TPA(812 Å)/Al at a voltage of 15.5 voltage. After treatment of ITO by O2 plasma, the performance of single-layer device ITO/POX-TPA(812 Å)/Al could be improved. The maximum brightness and photometric efficiency reached 55 cd/m2 and 0.014 cd/A, respectively, at a voltage of 9.5 V.

CONTENTS
ACKNOWLEDGEMENT i
ABSTRACT (ENGLISH) ii
ABSTRACT (CHINESE) iv
CONTENTS v
LIST OF TABLES ix
LIST OF FIGURES x
CHAPTER 1 INTRODUCTION 1
1.1 Preface 1
1.2 The conducting mechanism and electronic structure of conjugated polymer [22] 5
1.2.1 Metal-semiconductor contacts [25] 10
1.3 The luminescent principle of LEDs [26] 10
1.3.1 Phosphorescent energy transfer [29, 30] 14
CHAPTER 2 LITERATURE REVIEW 16
2.1 The characteristics of P-N diblock 16
2.1.1 Thiophene and oxadiazole 17
2.1.2 Carbazole and oxadiazole 18
2.1.3 PPV and oxadiazole 20
2.2 Hole transport layer 22
2.3 The cleaning of ITO 23
CHAPTER 3 EXPERIMENTAL 25
3.1 Materials 25
3.2 Synthesis of POX-TPA (Scheme 3.1) 27
3.2.1 N-type monomer 27
3.2.2 P-type monomer 30
3.2.3 Polymer synthesis 30
3.3 Device fabrication of Light-Emitting-Devices 31
3.3.1 The etching of ITO 31
3.3.2 The cleaning of ITO 31
3.3.3 Cathode evaporation 32
3.4 Characterization 33
CHAPTER 4 RESULTS AND DISCUSSION 37
4.1 The characterization of POX-TPA 37
4.2 UV-Vis absorption, photoluminescence fluorescence
spectra 49
4.2.1 Solvent effect 51
4.2.2 Fluorescence and UV-Vis spectra 55
4.3 Electrochemical characteristics 57
4.4 The effect of thickness 61
4.4.1 Fowel-Nordheim tunneling theory 64
4.5 Double-layer device 68
4.5.1 The measurement of stability 77
4.6 Treatment of indium-tin oxide 81
CHAPTER 5 CONCLUSION 91
REFERENCES 93
LIST OF SCHEME
Scheme 3.1. Synthesis of POX-TPA via Wittig
condensation route 28
LIST OF TABLES
Table 3.1 The relaton between colors and wavelengths 35
Table 4.1 The assignment of the peaks for IR spectrum
of POX-TPA 39
Table 4.2 The absorption and emission values of
POX-TPA solutions in different solvents 53
Table 4.3 The optical and electronic parameters for
POX-TPA 60
Table 4.4 The chemical compositions of ITO under different
O2 - plasma treatments 86
Table 4.5 The AFM images of ITO treated with different
O2 partial pressures 90
LIST OF FIGURES
Fig. 1.1 The common conjugated materials for light-
emitting diode. 4
Fig. 1.2 The band gap of (a) insulator, (b) semiconductor,
(c) metal [23] 6
Fig. 1.3 The energy levels of soliton, polaron,bipolaron 9
Fig. 1.4 The band diagrams of (a) PL and (b) EL [28]. 12
Fig. 1.5 The energy diagrams of fluorescence
and phosphorescence. 13
Fig. 3.1 The architecture of OLED. 32
Fig. 4.1 The FT-IR spectra of (a) p-type monomer and (b)
POX-TPA. 38
Fig. 4.2 The 1H-NMR spectrum of monomer 3. 41
Fig. 4.3 The 13C-NMR spectrum of monomer 3. 42
Fig. 4.4 The 1H-NMR spectrum of monomer 5. 43
Fig 4.5 The 13C-NMR spectrum of monomer 5. 44
Fig. 4.6 The 1H-NMR spectrum of POX-TPA. 45
Fig. 4.7 The 13C-NMR spectrum of POX-TPA. 47
Fig. 4.8 The GPC spectrum of POX-TPA. 48
Fig. 4.9 UV-Vis and PL spectra of POX-TPA thin film
and chloroform solution. 50
Fig. 4.10 The concentration-dependence of UV-Vis spectra:
(a) 1.7 x 10 — 4, (b) 1.7 x 10 - 5 (intensity
x 5), and (c) 1.7 x 10 - 6 M (intensity x 30)
and PL spectra: (d) 1.7 x 10 — 4, (e) 1.7
x 10 - 5, and (f) 1.7 x 10 - 6 M of POX-TPA
in chloroform. (Curves d, e, f are normalized). 52
Fig. 4.11 The (a) emission and (b) UV-Vis spectra of POX-TPA
in different solvents. 54
Fig. 4.12 The luminescence and UV-Vis spectra of the
POX-TPA films. 56
Fig. 4.13 The cyclic voltammogram of ferrocene/ferrocenium
in acetonitrile containing 0.1 M of n-Bu4NClO4
with a scan rate of 10 mV/s. 58
Fig. 4.14 The cyclic voltammogram of POX-TPA coated on
ITO electrode in 0.1 M of KCl with a scan rate
of 10 mV/s. 59
Fig. 4.15 The thickness dependence of (a) I-V (b) J-V (c)
J-E, and (d) B-V characteristics of ITO/
POX-TPA/Al. (i) 595, (ii) 812, (iii) 905,
and (iv) 1050 Å. 62
Fig. 4.16 The Fowler-Nordheim plot for 905 Å of device
at 298 k. 65
Fig. 4.17 The EL spectra of ITO/POX-TPA/Al: (a) 1050 and
(b) 595 Å devices under different bias voltages. 67
Fig. 4.18 The cyclic voltammogram of polyamide-imide coated
on ITO with a scan rate 10 mV/s. 70
Fig. 4.19 The UV-Vis spectrum of polyamide-imide in
NMP solution. 70
Fig. 4.20 The energy diagram of ITO/PPOX-TPA/Al
and ITO/polyamide -imide /POX-TPA/Al. 71
Fig. 4.21 The current-voltage-brightness characteristics of
(a) ITO/polyamide-imide/POX-TPA/Al and (b)
ITO/POX-TPA/Al. 73
Fig. 4.22 The efficiency-voltage characteristic of
(a) ITO/polyamide-imide/POX-TPA/Al and
(b) ITO/polyamide-imide/POX-TPA /Al. 74
Fig. 4.23 The (a) I-V and (b) B-V characteristics
of ITO/polyamide -imide/POX-TPA/Al. 76
Fig. 4.24 Stability measurement of ITO/POX-TPA/Al and
ITO/polyamide -imide/POX-TPA/Al. 78
Fig. 4.25 The stability of annealed and unannealed
single-layer devices at 70 0C. 78
Fig. 4.26 The pictures of (a) annealed device at 70 oC
and deposited with Al, and unannealed device,
(b) deposited with Al, (c) before deposited
with Al, and (d) after luminance by
optical microscopy measurement. 80
Fig. 4.27 (a)The current-voltage, (b) brightness-voltage,
and (c) efficiency-voltage characteristics
of single-layer LED for ITO glass treated
with O2 plasma’s pressure. (i) 0, (ii) 30,
and (iii) 60 mTorr. 82
Fig. 4.28 The chemical compositions of ITO treated with
O2 plasma’s pressure: (a) 0, (b) 30, and (c)
60 mTorr by x-ray measurement. 85
Fig. 4.29 The three dimensional AFM images of ITO treated
with O2 plasma’s pressure:(a) 0, (b) 30, and (c)
60 mTorr. 88

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