TiO2 나노와이어 구조를 이용한 염료감응형 태양전지의 효율 향상 연구

Abstract

Since pioneering work of Grätzel’s group in 1991, dye-sensitized solar cells (DSSCs) have been considered as promising and attractive 3rd generation photovoltaic cells and countless number of studies has done by numerous researchers all over the world. Typical DSSCs consists of conduction glass substrate such as FTO, wide-band gap semiconductor like TiO2 or ZnO, sensitizers such as ruthenium complex dye or organic dye, iodide or sulfide electrolyte, and Pt counter electrode. In this thesis, nanowire-based photoelectrodes have been developed to fabricate efficient DSSCs by suitably combining nanowires and nanoparticles. Prior to my research, the fundamentals of DSSCs were reviewed including the features, operation principle and components. From starting to look into components of DSSCs, understanding of photoelectrode is followed. It is a key role of photoelectrode in DSSCs to offer electron pathway and space for dye adsorption. We tried to promote their performance which is specified by increasing surface area, enhancing electron transport and working as light scatterer. At first, literatural survey about previous work on nanowire structured-photoelectrode was implemented. From the outstanding work of Griem’s et al. in 2008, we could get vertically high crystalline TiO2 nanowire arrays photoelectrode and modified efficiently. For the sake of optimum condition of pristine nanowire arrays, morphology of nanowire arrays was controlled in thickness, porosity and diameter. While finding best condition of nanowire arrays for bilayer and composite structure, we could obtain 20 μm and compare the DSSCs photovoltaic performance according to different thickness. Bi-layer photoelectrode with TiO2 nanowires and TiO2 nanoparticles DSSCs which has nanoparticles layer on the nanowire arrays was prepared by doctor blade method and the properties of bilayer photoelectrode such as morphology, structure and photovoltaic performance was observed. Because of nanoparticles layer working as electron highway, bilayer photoelectrode DSSCs promoted short-circuit photocurrent density, Jsc attributed to increased surface area for dye adsorption.Composite structure photoelectrode with TiO2 nanowires and TiO2 nanoparticles DSSCs was obtained and discussed. By irradiating of ultra-sonication, nanoparticles could deposit on the individual nanowire which enhance the surface area of pristine nanowire arrays. Characterizing each type of photoelectrode based on pristine nanowire arrays was implemented in every discussion. HR-SEM and X-ray diffraction was employed for structural property. UV-Vis spectral scopy analysis was done by attaining reflectance and absorbance spectra. Verifying the relation between structural property and photovoltaic performance, solar cell quantum efficiency was observed by IPCE measurement and overall conversion efficiency was examined.