Photoresponsive Electrical Property of Hybrid Nanostructures Based on Poly (3-hexylthiophene)
- 주제(키워드) Hybrid Nanostructure , Coaxial Nanotube , Composite Nanowire , Poly (3-hexylthiophene) , Photoresponsive Electrical Property
- 발행기관 고려대학교 대학원
- 지도교수 주진수
- 발행년도 2011
- 학위수여년월 2011. 2
- 학위구분 박사
- 학과 일반대학원 물리학과
- 세부전공 고체물리학 전공
- 원문페이지 153 p
- 실제URI http://www.dcollection.net/handler/korea/000000024568
- 본문언어 영어
- 제출원본 000045642271
초록/요약
Photoresponsive electrical properties of hybrid nanotube (NT) and nanowire (NW) using π-conjugated materials were studied in this dissertation. The coaxial NTs of multiwalled carbon nanotubes (MWCNT) coated with light-emitting poly (3-hexylthiophene) (P3HT) were fabricated through electrochemical deposition of 3-HT monomers onto the surface of the MWCNT. The composite NWs with heterojunction of the P3HT and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were prepared through wetting process based on Al2O3 template. The formation of the hybrid NTs and NWs was visualized by scanning electron microscope and transmission electron microscope images. The optical and structural properties of the hybrid NTs and NWs have been characterized using UV/Vis, Raman, FT-IR, and photoluminescence spectra. The photoresponsive current-voltage (I-V) characteristics were measured for the single strand of the hybrid NTs and NWs. For the single P3HT/MWCNT hybrid coaxial NT, the I-V characteristics of the outer P3HT single NT showed the semiconducting behavior, while ohmic behavior was observed for the inner single MWCNT. The I-V characteristics of the hybrid junction between the outer P3HT NT and the inner MWCNT, for the hybrid single NT, exhibited the characteristics of a diode (i.e., rectification), whose efficiency was clearly enhanced with light irradiation. The rectification effect of the hybrid single NT has been analyzed in terms of charge tunneling models. The quasiphotovoltaic (PV) effect was also observed at low bias for the P3HT/MWCNT single hybrid NT. The power conversion efficiency, η, of the single hybrid NT was ∼0.42%. For the single P3HT:PCBM composite NW, the I-V characteristics showed diode-like behaviors for the three different concentration (P3HT:PCBM wt.%=1:1, 1:2, and 1:4) due to the formation of energy barriers. Under light illumination, the current level of the composite NW was enhanced with applied bias. Charge transport mechanism of the single P3HT:PCBM composite NW was analyzed in terms of Schottky emission and space charge limited conduction model. The photocurrent of the single P3HT:PCBM composite NW in high forward bias region (≥ 35 V) has been analyzed using a space charge limited photocurrent model. The PV effect with η=0.14% was observed in the PV cells using the P3HT:PCBM composite NWs. Photoresponsive charge transport characteristics including a PV effect for the single strand of the hybrid NTs and NWs based on P3HT were discussed.
more목차
Abstract i
Contents iv
List of Tables vii
List of Figures viii
1 Introduction 1
References 5
2 Theoretical Background 7
2.1 π-Conjugated Materials . . . . . . . . . . . . . . . . . . . . . .7
2.1.1 Semiconducting Polymers . . . . . . . . . . . . . . . . . . 7
2.1.2 Carbon Nanotubes . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.3 Fullerene and It’s Derivatives . . . . . . . . . . . . . . . . 14
2.1.4 P3HT:PCBM Composites . . . . . . . . . . . . . . . . . . 17
2.2 Charge Transport Mechanisms . . . . . . . . . . . . . . . 19
2.2.1 Space Charge Limited Conduction Model . . . . . . . 19
2.2.2 Fowler-Nordheim Tunneling Model . . . . . . . . . . . . 22
2.2.3 Transition of Charge Tunneling . . . . . . . . . . . . . . 26
2.3 Photoresponsive Electrical Characteristics . . . . . . . . 29
2.3.1 Space Charge Limited Photocurrent . . . . . . . . . . . 29
2.3.2 Photovoltaic Effect . . . . . . . . . . . . . . . . . . . . . . . 32
References 42
3 Experimental 46
3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.1.1 P3HT/MWCNT Coaxial Nanotubes . . . . . . . . . . . . 46
3.1.2 P3HT:PCBM Composite Nanowires . . . . . . . . . . . 49
3.2 Device Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.2.1 Electron Beam Lithography . . . . . . . . . . . . . . . . . 51
3.2.2 Device Fabrication Process . . . . . . . . . . . . . . . . . 60
3.3 Experiments for Characteristics . . . . . . . . . . . . . . . 63
3.3.1 Structural and Optical Characteristics . . . . . . . . . . 63
3.3.2 Photoresponsive Electrical Characteristics . . . . . . 64
References 67
4 Results and Discussion 68
4.1 P3HT/MWCNT Coaxial Nanotubes . . . . . . . . . . . . . 68
4.1.1 SEM and TEM Images . . . . . . . . . . . . . . . . . . . 68
4.1.2 Raman Spectrosopy . . . . . . . . . . . . . . . . . . . . . 70
4.1.3 Infrared Spectroscopy . . . . . . . . . . . . . . . . . . . . 74
4.1.4 Ultraviolet/Visible Spectroscopy . . . . . . . . . . . . . . 77
4.1.5 Photoluminescence . . . . . . . . . . . . . . . . . . . . . . 79
4.1.6 Quantum Yield . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.1.7 Electrical Characteristics . . . . . . . . . . . . . . . . . . . 84
4.1.8 Charge Transport Properties . . . . . . . . . . . . . . . . 88
4.1.9 Photoresponsive Electrical Characteristics . . . . . . 93
4.1.10 Photovoltaic Effect . . . . . . . . . . . . . . . . . . . . . . . 96
4.2 P3HT:PCBM Composite Nanowires . . . . . . . . . . . . . 99
4.2.1 SEM and TEM Images . . . . . . . . . . . . . . . . . . . . 99
4.2.2 Raman Spectrosopy . . . . . . . . . . . . . . . . . . . . . 101
4.2.3 Ultraviolet/Visible Spectroscopy . . . . . . . . . . . . . 105
4.2.4 Photoluminescence . . . . . . . . . . . . . . . . . . . . . 109
4.2.5 Electrical Characteristics . . . . . . . . . . . . . . . . . . 114
4.2.6 Charge Transport Properties . . . . . . . . . . . . . . . . 118
4.2.7 Photoresponsive Electrical Characteristics . . . . . . 122
4.2.8 Photovoltaic Effect . . . . . . . . . . . . . . . . . . . . . . . 127
References 129
5 Conclusion 134
Summary (in Korean) 136
