由於奈米碳管之層與層間有凡得瓦力存在，及其近於單軸結構而造成強大的熵，故容易聚集因而降低其優異的光電特性，限制了許多方面的應用。在此研究，運用了化學改質接支上不同長碳鏈的懸垂基(-COOC4H9，-COOC10H21，和 -COOC18H37)來降低多層奈米碳管的長寬比，促進分散性，進而探討光電與導電性臨界現象。由傅立葉轉換紅外線吸收光譜觀察多層奈米碳管衍生物，在吸收光波段2917 cm-1，2846 cm-1及在1733 cm-1可分別觀察到烷基(C-H)和酯基(C=O)的特徵峰。液態核磁共振儀亦可測量到在化學位移δ = 3.64 ppm (OCH2)的吸收峰，δ = 1.25 ppm (CH2)的吸收峰及δ = 0.88 ppm (CH3)的吸收峰。並經由拉曼光譜儀發現，經過酯化接支促使吸收峰積分比值(ID/IG)有下降的趨勢。
在應用方面，將化學改質後的多層奈米碳管依不同比例摻入聚3-己烷基噻吩並澆鑄成膜及量測其導電度，可發現隨著奈米碳管含量增加，平行膜面導電度從未摻雜前的1.4×10-6 S/cm巨增到1.2×10-2 S/cm。且臨界導電度會隨著奈米碳管長寬比增加而有下降之趨勢。造成此現象是因為奈米碳管間的距離已足夠讓電荷跳躍傳遞於高分子間。在異質界面之太陽能電池應用方面，藉著導入奈米碳顆粒－苯丁酸甲酯，製作成ITO/PEDOT:PSS/MWCNT:[PC61BM:P3HT]/LiF/Al的多層接面結構，且將改質後的多層奈米碳管含量改變，混摻於苯丁酸甲酯和聚3-己烷基噻吩(0.8:1)的基材。伴隨著添加0.01 wt. %改質短懸垂基(-COOC4H9)的多層奈米碳管，此太陽能電池元件可達到近乎於4 %的光電轉換效率。

Due to entropy and Van der Waals’ interaction, carbon nanotubes tend to aggregate degrading their excellent opto-electronic properties and limiting their applications. Chemical derivatizations were applied to the multi-wall carbon nanotube (MWCNT) by esterificating with different lengths of aliphatic pendants (COOC4H9, COOC10H21, and COOC18H37) to decrease the MWCNT aspect ratio to facilitate its dispersion, and to observe its percolation behavior. FTIR analysis revealed the more relevant absorption peaks of C-H at 2917 cm-1, 2846 cm-1 and C=O at 1733 cm-1 from the derivatization. H1-NMR showed that the aliphatic pendant functionalized MWCNT from the signals of OCH2 at δ = 3.64 ppm, CH2 at δ = 1.25 ppm, and CH3 at δ = 0.88 ppm. Raman scattering indicated that esterification caused the ID/IG absorption peak area ratio to decrease.
In applications, the electric conductivity was measured on thin-films of MWCNT:Poly-(3-hexylthiophene) (P3HT) as a function of nanotube content. Accompanied with nanotube doping concentration increased, the electric conductivity parallel to film surface (σ||) could range from an undoped value 1.4×10-6 S/cm up to 1.2×10-2 S/cm. The conductivity percolation threshold concentration decreased as the MWCNT aspect ratio increased due to the average distance between the nanotubes becoming sufficiently small for charges to hopping through P3HT. By incorporating [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), bulk heterojunction photovoltaic (PV) cells of ITO/PEDOT:PSS/MWCNT:[PC61BM:P3HT]/LiF/Al were fabricated. By varying the ratio of MWCNT to the PC61BM:P3HT (0.8:1) mixtures, the PV cells showed the maximum power conversion efficiency (ηp) close to 4 % with MWCNT-COOC4H9 at a doping concentration of 0.01 wt. %.

CATALOGUE
FIGURE CAPTIONS IV
TABLE CAPTIONS IX
I. INTRODUCTION 1
1.1 Preface 1
1.2 Organic Photovoltaic Cell Background 1
1.2-1 Evolution 1
1.2-2 Single Layer Device 3
1.2-3 Bilayer Device 4
1.2-4 Bulk Heterojunctions 5
1.3 Organic Conjugated Polymer 6
1.4 Carbon Nanotube and Related Properties 8
1.4-1 Multi-Wall Carbon Nanotube (MWCNT) 8
1.5 Research Motivation 9
II. PRINCIPLE AND REFERENCE REVIEW 11
2.1 Principle 11
2.1-1 Oxidation Mechanism 11
2.1-2 Esterification Mechanism 11
2-1-3 Transfer of Excitation 12
2.1-4 General Mechanisms in Photovoltaic Cells 13
2.1-5 Solar Irradiance Simulation 14
2.1-6 Equivalent Circuit of a Solar cell 15
2.1-7 Efficiency Parameters 17

III. EXPERIMENT 22
3.1 Experimental Chemicals 23
3.2 Chemical Derivatization of MWCNTs 24
3.2-1 Purification of MWCNTs 25
3.2-2 Acid Oxidation of p-MWCNTs 25
3.2-3 Acid Chloride Reaction of o-MWCNTs 26
3.2-4 Esterification of MWCNTs 26
3.3 Photovoltaic Cell Processing 28
3.3-1 Preclean ITO Substrate 28
3.3-2 Solution Preparation 28
3.3-3 Device Fabrication 29
3.4. Four-Probe Direct Current Conductivity Measurement 31
3.5 Instruments for Chemical Analyses 32
3.5-1 Fourier Transform Infrared Spectrometer (FTIR) 32
3.5-2 1H Nuclear Magnetic Resonance (1H-NMR) 33
3.5-3 Raman Spectroscopy 34
3.6 Device Fabrication and Measurement 35
3.6-1 O2 Plasma Cleaner 35
3.6-2 Spin Coater 35
3.6-3 Vacuum Thermal Evaporator 36
3.6-4 Glove Box System 37
3.6-5 Keithley® 2400/Source Measure Meter 38
3.6-6 Keithley® 237/Source Measure Unit 39


IV. RESULTS AND DISCUSSION 40
4.1 FTIR Analysis of the Chemically Derivatized MWCNT 40
4.2 1H-NMR Analysis of Chemical Synthesis Product 43
4.3 Raman Scattering Analysis of the Chemical Synthesis Product 48
4.4 Electric Conductivity with Derivatized MWCNT Dopants 54
4.4-1 Electric Conductivity with MWCNT-COOC4H9 Dopant 55
4.4-2 Electric Conductivity with MWCNT-COOC10H21 Dopant 62
4.4-3 Electric Conductivity with MWCNT-COOC18H37 Dopant 67
4.4-4 Percolation Behavior and Aspect Ratio of Derivatized MWCNT 71
4.5 Characteristics of Derivatized MWCNT Doped PV Devices 74
4.5-1 Characteristics of MWCNT-COOC4H9 Doped PV Device 75
4.5-2 Characteristics of MWCNT-COOC10H21 Doped PV Device 76
4.5-3 Characteristics of MWCNT-COOC18H37 Doped PV Device 78
4.5-4 Comparison of MWCNT:[PC61BM:P3HT] PV Device 79
V. CONCLUSIONS 88
VI. REFERENCES 91

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