탄소 나노튜브의 광/전자 소자 응용

Abstract

Encapsulation of organic molecules inside carbon nanotubes (CNTs) and CNTs-inorganic thin film or nanoparticle composite system benefit from electronic energy structure modulation and the generation of high electric filed across the inorganic thin film. The hybrid composite structures have attracted considerable attention as the next generation structures because they combine the advantages of both inorganic and organic structures. CNT-organic /inorganic hybrid composite synthesized by encapsulation and surface deposition work can be easily applied to photonic and electronic device such as field emission emitter, secondary electron emitter, photon detectors, particularly in improved power conversion efficiency of solar to electrical energy conversion devices (solar cell). Chapter I introduces a brief history and basic properties of research on the carbon nanotubes and the goal of this research. Chapter II reviews synthesis 1-(2-amino-phenyl) naphthalene-2-ylamine (APNA) and insertion them into the inside SWNTs. photoluminescence spectra of APNA molecule after encapsulation were obtained for the first time. Analysis of those spectra revealed that the APNA withdrew electrons from the SWNT, and also supplied the information about the ground and excited-geometry after encapsulation. Chapter III 1. describes the field emission characteristics of indium oxide In2O3-coated single-walled carbon nanotubes (SWNTs). Scanning electron microscopy, x-ray diffractometer, and UV/visible spectroscopy confirmed that In2O3 exists as a polycrystalline cubic bixbyite structure on thesurface of SWNTs. In2O3-coated SWNTs with optimal coating thickness decrease turn-on field and increase maximum current density. 2. Field emission properies were characterized for prinstine single-walled carbon nanotubes and after encapsulation of electron withdrawing and donating molecule, i.e., 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and tetrathiafulvalene (TTF). FE properties are changed by electron donation or acception properties of encapsulated molecules. Chapter IV reports the enhanced photocurrent and relative quantum efficiency of cesium iodide (CsI) films on magnesium oxide (MgO)-coated multiwall carbon nanotubes (MWNTs) on a silica substrate, i.e., CsI/MgO/MWCNTs/Si, when illuminating with 147 nm photons under an external electric field. The incorporation of MWCNTs resulted in significant enhancement of the photocurrent by several orders of magnitude compared to that of a conventional CsI. An analysis of the photoelectron energy spectrum attributed the phenomena to the creation of a very high electric field through the MgO/CsI film with the subsequent generation of avalanche secondary electrons. Chapter V proposed evaluation method for miniaturized gas-ionization sensor based on 3-dimensional network single-walled carbon nanotube inside porous silicon (3-D SWNT network inside PS) at normal temperature and pressure. It is possible to identify one gas or certain mixture gas, as different gases have their unique breakdown voltage and discharge current. The miniaturize 3-D SWNT network inside PS based gas-ionization sensor high accuracy, repeatability, stability and safe operation condition. This sensor is promising for use in various fields. Chapter VI shows simple methode for phase separation of single carbon nanotube (SWNT) in the view of electrical properties. SWNTs synthesized through chemical vapor deposition on silicon substrates. The synthesis resulted in three different micro-structures under the same growth conditions: (1) mirror polished, (2) chemically etched (large pattern), and (3) chemically etched (large pattern). Changes of field emission (FE) and electronic structure of the SWNTs were explored. Chapter VII 1. Using reverse-field emission (FE) current measurements, we demonstrate enhancement of the electric field by single-walled carbon nanotubes (SWNTs) in In2S3/In2O3 photoelectrochemical solar cells (PECs). In reverse-FE measurements, anode and cathode consists of In2S3/In2O3/(with or without) SWNTs on indium-doped tin oxide substrate and micro-texturized tip silicon, respectively. The enhanced FE results for In2S3/In2O3/SWNTs show an electric field ~2 times more than In2S3/In2O3. In PECs, the enhanced electric field intensifies the power of electron transfer, which accelerates the electron transfer rate in the cell. 2. C60 molecules encapsulation singlewalled carbon anotube (C60@SWNT or Peapod) film which has fibrous morphology and network structure on ITO were prepared to exploit high surface area and effected the efficiency of RuL2(NCS)2/DAPV/SWNTs and RuL2(NCS)2/DAPV/peapods photoelectrochemical cells by ehanced charge-collection and reduced recombination reaction. Chapter Ⅷ shows the possibility of making infrared solar cells based on p/n-silicon and p-type pristine SWNTs that serve as the energy conversion material and charge transport electrode. It is demonstrated that SWNTs can be used to convert the infrared light into the electrical energy under the configuration of solar cells. Moreover, application of SWNTs are found to show the better power conversion efficiency than pristine Si solar cell. Chapter Ⅸ Charge carrier mobility and recombination in a Si and inorganic solar cell has been studied using the novel technique of photoinduced charge carrier extraction in a linearly increasing voltage (Photo-CELIV). In this technique, charge carriers are photogenerated by a short laser flash, and extracted under a reverse bias voltage ramp after an adjustable delay time (tdel). Furthermore, determination of charge carrier lifetime, mobility and diffusion length is presented.

As a result, these results presented in this thesis can pave the way for appication of carbon nanotubes in Photonic and Electronic Devices.