A Study on Physical and Electric Properties of Carbon Nanotube and It's Application to Photoelectric Device

Abstract

Carbon nanotube (CNTs) have excellent properties of electric and chemical stability, so it research at various field such as sensor, solar cell and display. CNTs can be adjust energy level and advantage high electric field by encapsulation and coated with organic/inorganic material. The composite hybrid single-walled carbon nanotubes (SWNTs) has advantage of organic and inorganic material, it will be next generation material including graphene. In this thesis, we made composite modified SWNTs by encapsulation and coating method, analyze their properties. In addition, the possibility for various application using SWNTs was confirmed. Chapter Ⅰ introduces a history, typical properties of CNTs, application and purpose of this thesis. Chapter Ⅱ describes properties of modified SWNTs. First, 1-(2-amino-phenyl) naphthalene-2-ylamine (APNA) molecules encapsulated inside single-walled carbon nanotubes (APNA@SWNTs) in vacuum. Here we measured X-ray diffraction (XRD) pattern and attenuated total reflectance (ATR) spectrum to confirm the encapsulation of APNA molecules inside SWNTs.. The PL intensity was proportional to suspension stability of SWNTs in various solvents. Second, we confirmed characteristic of iodine intercalated SWNTs (I-SWNTs) by Field-effect transistors (FETs). Iodine molecules are chosen for intercalation to SWNTs to predict the charge transfer tendency between them. FETs using I-SWNTs are fabricated and their electronic properties are investigated to better understand the charge transfer between iodine and SWNTs by changing gate voltages. Under vacuum, I-SWNTs FETs exhibit weak n-type character, indicating that electrons are transferred slightly from the iodine to the SWNTs. After exposure to O2 gas, n-type characters are reduced; however, they still retain their original type. Third, we discusses field emission properties of In2O3 coated SWNTs. In2O3 nanoparticles are coated on the surfaces of SWNTs by a successive ionic layer adsorption and reaction (SILAR) process. Field enhancement of the In2O3-coated SWNTs is confirmed by conductive atomic force microscopy (c-AFM) and field emission (FE) analysis. Near infrared (NIR) and X-ray photoemission spectroscopy (XPS) data are suggested to explain the charge transfer and bandgap change between the In2O3 nanoparticles and SWNTs and the electric field enhancements in the In2O3-coated SWNTs. Chapter Ⅲ reports application about SWNTs. First section characteristic FE properties of SWNTs synthesized inside the pores as well as on the top surface of a porous silicon (PS) substrate. Turn-on fields and emission current densities were measured and compared with those of other types of SWNTs in similar environments. A life-time stability test was performed by monitoring the current density before and after repeated exposure to O2, suggesting that the pore channel can effectively prevent O2+ ion etching from destroying SWNTs within the pores of the PS layer. Second section investigate new type of silicon solar cell with SWNTs. We made silicon solar cell without SWNTs, with SWNTs at front side and with SWNTs at front and rear side. Power conversion efficiency of each solar cell and incident photon to converted electron interpret that SWNTs absorbed at the infrared light and decreased series resistance at interface between metal electrode and silicon substrate. According to technique of photo-induced charge carrier extraction in a linearly increasing voltage (Photo-CELIV), SWNTs can be made to increase mobility, bimolecular lifetime.