在本論文中，我們以最新合成的三種不同紫質晶體 (TEPyP-離子)，研究其光學與電學的性質。在電學方面，它的導電率，在沿著分子的堆疊方向上，展現高度的異向性。以樣品TEPyP-4I而言，它在平行於分子的堆疊軸線上有著導電率3.2 ，是垂直分子堆疊軸線的導電率的一千倍。在溶液的吸收光譜中，這些晶體的溶液在紫外線區域出現強烈的吸收尖峰 (B區), 而在可見光區中出現四支弱的吸收尖峰 (Q區)。我們比較溶液與晶體的吸收光譜；晶體在B區的尖峰呈現藍移0.09電子伏特的結果，在Q區的尖峰則呈現紅移0.05 - 0.09電子伏特的結果，這些能量的偏移歸因於紫質分子間激子耦合的交互作用。紫質晶體的螢光光譜也被詳細量測，在特定激發波長的雷射下，經由發射與吸收光譜的鏡像理論，螢光光譜可以用以推測晶體吸收光譜的能隙。我們同時發現同種樣品的側面與頂面的能隙的不同與能量偏移。在紫質晶體的偏極反射光譜上，由於反射率的異向性，使得電場平行於分子平面時有較大的反射率。藉由介電函數模型的分析，我們算出關於樣品TEPyP-4I電子躍遷的每支吸收尖峰的複數介電函數、光學導電率與電漿頻率。此外，紫質晶體的傅立葉紅外線轉換光譜也被研究分析，各個特徵吸收尖峰被分別解釋。最後，我們利用最新合成的鋅紫質衍生物做成有機薄膜電晶體的活化層；將晶體以適當比例溶於&;#21537;啶中，以旋轉塗佈機將此溶液均勻塗佈在二氧化矽基板上，在充滿氬氣的高溫爐內，溶液成為大區域、均勻的多晶薄膜。交叉指狀的金源極與金汲極在充滿氬氣的離子濺鍍機中以金鈀材完成，用以有效收集更多晶體內由電場引起的載子。在完成的此電晶體中，我們以電洞通道、載子累積的模式操作它。線性區與飽和區可以在電流輸出特性曲線與轉換特性曲線中被量測出來。載子的電場效應流動率、臨界電壓以及開關比同時被計算出來。我們的結果顯示出以長烷基邊鏈取代的紫質可以大大增加其溶解度使能製成薄膜。我們可以較低的退火溫度製造出有機薄膜電晶體。

In this research we investigate the transport and optical properties of three kinds of single crystals 5,10,15,20-tetrakis (4-N-ethylpyridyl) porphyrin salts (TEPyP-ions). The electrical conductivity exhibits high anisotropy, in that the conductivity along the stacking column, which is equal to 3.2 for sample TEPyP-4I, is three orders of magnitude larger than that perpendicular to the stacking column. In comparison to the solution spectra, the crystal spectra exhibit a blue shift of 0.09 eV in the B band and red shifts of 0.05 - 0.09 eV in the Q bands. The energy shifts are attributed to the exciton coupling interaction of the porphyrin molecules. Polarized reflectance measurements of the crystals reveal that the anisotropic reflectance is most intense when the light polarization is parallel to the molecular plane. The complex dielectric function and optical conductivity associated with each electronic transition are calculated based on analysis with a dielectric-function model. We also investigate the organic thin-film transistors fabricated employing the newly synthesized compound 5,10,15,20-(tetrakis(4-dodecoxylphenylethynyl)porphyrinato) zinc(II) (Zn-TDPP) as the active layer. The porphyrin was processed with side-chain substitution in the meso-position of the macrocycle. The organic film deposited by spin coating from a pyridine solution before being annealed in a furnace in argon gas to form homogenous polycrystals. Staggered source and drain gold contacts were made by argon ion sputtering with a stencil plate. The organic field-effect transistor (OFET) operates in the p-channel, accumulation-mode. The linear and saturation regimes were identified from the output and transfer characteristics. Carrier mobility, threshold voltage and ON/OFF ratio were calculated. The results show that the side-chain substitution greatly increased the solubility of the Zn-TDPP. The solution-processing technique can be used to fabricate porphyrin thin-film OFETs with a lower annealing temperature.

Acknowledgement........................................................................................ i
Summary (Chinese)...................................................................................... ii
Summary (English)......................................................................................iii
Contents …………………………….………………….….................……iv
List of tables……………………………………………...............……….vi
List of illustrations………………………..............................................…vii
Chapter 1 : Preface
1.1 Motivation and background of this research.................................1
1.2 Molecular structures of porphyrins.............................................. 5
1.3 The porphyrins used in this research.............................................6
1.4 Theoretical background...............................................................12

Chapter 2 : The optical properties in porphyrins
2.1 The absorption spectra of porphyrin solutions
2.1.1 Introduction ……………………………..….................…16
2.1.2 Experiment …………………………..……….........…….16
2.1.3 Results and discussions …………………..….............…..17
2.2 The photoluminescence spectra of porphyrin single crystals
2.2.1 Introduction ……………………………..….........………21
2.2.2 Experiment ……………………………..….........……….22
2.2.3 Results and discussions ………………..…….........……..24
2.3 The reflection spectra of porphyrin single crystals
2.3.1 Introduction.…………………………………..............….29
2.3.2 Experiment ………………………………….............…...29
2.3.3 Results and discussions ……………………….........……31
2.4 The infrared absorption spectra of porphyrin crystals
2.4.1 Introduction ……………………….…...…............……..47
2.4.2 Experiment ………………………...…..…….…......…...48
2.4.3 Results and discussions …………..….......….…......……50

Chapter 3 : The transport properties of porphyrin crystals
3.1 Introduction …………………………….…............….………..54
3.2 Experiment ………………………………....…........………….55
3.3 Results and discussions …………………...............….………..57

Chapter 4 : The organic field effect transistors (OFET) based on porphyrins
4.1 Introduction ………………………………....….....…......…….62
4.2 Experiment ………………………………...…..….......……….64
4.3 Results and discussions ………………….........……........…….66

Chapter 5 : Conclusion
5.1 Conclusions.................................................................................71
5.2 Future works and suggestions.....................................................72
Reference ……………………………..……................…….….............73
List of tables
Table 2.1.Observed electronic absorption maxima for the TEPyP-4I solution........20
Table 2.2 Energy gap (Eg) of porpyrin crystals on side face and top face…….…....…27
Table. 2.3 Polarized reflectance spectra of three porphyrin crystals...............................36
Table 2.4 Fitting parameters of the six oscillators used in Eqs. 3 and 4.........................39
Table 2.5 B-band plasma frequency as a function of the angle φ…………...…………41
Table 2.6 The modes of vibrational motion in a molecule......................................…....48
Table 2.7 IR absorption peaks and the mechanisms……………………………...........51
Table 3.1 Transport conductivity parameters for TEPyP-4I porphyrin crystals…….....61


List of illustrations
Fig. 1.1 The numbered nomenclature of porphyrin by IUPAC.........................................5
Fig. 1.2 The metallic porphyrin ........................................................................................5
Fig. 1.3 (a) Molecular structure of free-base porphyrin
(b) Structure of TEPyP-4I, the building block of the porphyrin crystal.
(c) Molecular stacking along the axis.
(d) Projection of the porphyrin molecules onto the (010) plane.
(e) Dimeric units viewed down the axis.
(f) Hexagonal packing structure of porphyrin columns.
(g) Microscopic image of a porphyrin crystal..............................…....................8
Fig. 1.4 (a) Structure of TEPyP-6I, the building block of the porphyrin crystal.
(b), (c) Molecular stacking along the axis.
(d) Microscopic image of a porphyrin crystal......................................................9
Fig. 1.5 (a) Structure of TEPyP-2CdI4, the building block of the porphyrin crystal
(b), (c) Molecular stacking along the axis.
(d) Microscopic image of a porphyrin crystal...................................................10
Fig. 1.6 Structure of TPyP...............................................................................................11
Fig. 1.7 Structure of Zn-TDPP .......................................................................................11
Fig. 1.8 π→π* transitions happened in the unsaturated molecules............................12
Fig. 1.9 A new model include the 5th orbital...................................................................14
Fig. 1.10 Two electrons in HOMO ground state form a singlet......................................14
Fig. 2.1 The schematic spectrometer to measure absorption spectra of solutions..........16
Fig. 2.2 Absorption spectra of four porphyrin solutions.................................................18
Fig. 2.3 Optical absorption as a function of photon energy at room temperature...........18
Fig. 2.4 The fit of Lorenz oscillating model....................................................................20
Fig. 2.5 Configuration diagram for two electronic state in a molecule...........................21
Fig. 2.6 Illustration of the measurement of photoluminescence spectrum......................23
Fig. 2.7 Definitions of top face and side face .................................................................24
Fig. 2.8 PL spectra of three porphyrin crystals................................................................25
Fig. 2.9 PL spectra of TEPyP-2CdI4 on side face and top face.......................................25
Fig. 2.10 Absorption and emission spectra of the ladder polymer MeLPPP ..................26
Fig. 2.11 The mirror symmetry of PL spectrum and absorption spectrum of solution in TEPyP-6I...........................................................................................................28
Fig. 2.12 Illustration of polarized reflectance spectra.....................................................30
Fig. 2.13 Polarized reflectance spectra of TEPyP-2CdI4 crystal on
(a) side face
(b) top face.........................................................................................................32
Fig. 2.14 Polarized reflectance spectra of TEPyP-6I crystal on
(a) side face
(b) top face.........................................................................................................34
Fig. 2.15 Polarized reflectance spectra of TEPyP-4I crystal on
(a) side face
(b) top face.........................................................................................................35
Fig. 2.16. (a) Polarized reflectance spectra of porphyrin crystals.
(b) Schematic diagram shows that the spectra were measured.......................37
Fig. 2.17 Room-temperature
(a) complex dielectric function and
(b) optical conductivity spectra..........................................................................40
Fig. 2.18 Dependence of plasma frequency on φ.........................................................42
Fig. 2.19. (a) Optical absorption as a function of energy for the porphyrin solution and crystal.
(b) Schematic diagrams illustrate the angle α between the electric dipole moments μA, μB of two molecules...................................................................43
Fig. 2.20 Schematic diagram of Fourier transform infrared spectrometer (FTIR)..........49
Fig. 2.21 The infrared absorption spectra of porphy crystals in the range of
(a) 400 to 2400 cm-1
(b) 2400 to 4000 cm-1......................................................................................50
Fig. 3.1 (a) Schematic diagram of four lead method on a porphyrin crystal along the molecular stacking axis.
(b) The picture of (a).
(c) Schematic diagram of van der Pauw method on the top face of porphyrin crystal.
(d) The top view of sample.............................................................................55
Fig.3.2 (a) I-V curve of porphyrin crystal along stacking axis under varied temperatures,
(b) σ v.s. T for three samples along stacking axis.........................................57
Fig. 3.3 Electrical conductivity as a function of temperature in TEPyP-4I crystals for
(a) parallel to the stacking axis
(b) perpendicular to the stacking axis.............................................................59
Fig. 4.1. (a) Polycrystalline film prepared under the optimal condition of 130 ˚C for 20 min;
(b) amorphous film prepared at 170 ˚C for 10 min
(c) Thickness of the film was measured by AFM............................................63
Fig. 4.2 (a) Schematic diagram of the Zn-TDPP OFET
(b) Top view of the OFET before applying the Ag past..................................64
Fig. 4.3 Output characteristics of OFETs based on Zn-TDPP.........................................66
Fig. 4.4 Linear-regime transfer characteristics of Zn-TDPP OFETs...............................67
Fig. 4.5 Saturation-regime transfer characteristics of Zn-TDPP OFETs.........................69

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