공정제어에 의한 TCO-less 염료감응 태양전지 최적설계에 관한 연구

Abstract

Renewable energy consists of the resources which continue to restore without human involvement. These resources include solar, wind, geothermal and hydro energies. Fossil fuels, such as coal and oil are non-renewable. They are produced when plant and animal matter decays within the earth-crust & this process takes a substantial amount of time to form usable fuel. These resources have proved their effectiveness for the progress of world economy. However, in the coming future the energy consumption and, therefore, total energy demand is going to increase with the ever increasing population. The environmental issues such as greenhouse gas emissions and their impact on weather and climate which are also one of the concerns of using the non-renewable energy resources have encouraged the research for advancement of green energy and implementation of energy saving green technologies. Moving towards the clean and environment friendly renewable energy resources would be the future of energy sector. Recent past have seen the high increase in the cost of coal and oil which also led to the intensive research in different renewable energy sectors focusing on reducing their manufacturing costs. There are different kinds of renewable energies such as wind energy, hydro energy, geothermal energy, solar energy, tidal energy etc. Photovoltaic is a simple and elegant method of harnessing the sun's energy. Solar cells are unique in that they directly convert the incident solar radiation into electricity, with no noise, pollution or moving parts, making them robust, reliable and long lasting. The solar cell is the main component of PV systems. It converts solar energy directly into the usable direct-current (DC) electricity. For more than two decades, dye-sensitized solar cells (DSSCs) have been intensively investigated in industry and academia as a viable alternative to conventional silicon-based photovoltaic cells because of relatively their low cost and high efficiency. Typically, DSSCs are composed of a mesoporous titania nanocrystal electrode on a transparent conductive oxide (TCO) substrate with ruthenium-based sensitizers on the titania nanocrystals, platinum on the TCO substrate as a counter electrode, and iodine/iodide electrolyte between the two TCO substrates. The high costs of these materials is an obstacle and prevents the commercialization of DSSCs. In this thesis, a TCO-less DSSC with a carbon (C) working electrode was first briefly report by using a dual magnetron sputtering method. The film thickness of sputter-deposited C was varied for determination of the optimal condition for the best photovoltaic performance. Carbon thin films grown by magnetron sputtering method were exhibited higher crystallinity with the increase of film thickness, resulting in uniform and large grain size. Also, the electrical properties of carbon films are improved with the increase of film thickness. In the results, the performance of TCO-less DSSC critically depended on the film thickness of working electrodes, indicating the conductivity of carbon thin films. In the second work, titanium-coated carbon (TiC) thin film was applied to TCO-less DSSC as a working electrode. The efficiency of TiC-based TCO-less DSSC was significantly dependent on film thickness. In the third work, titanium metal electrode was investigated to apply to the TCO-less DSSC as a workinng electrode. The optimal thickness of Ti thin film for the best photovoltaic performance was 100nm with the cell efficiency of 4.21%. The photovoltaic properties of TCO-less DSSC were investigated using various analysis methods. The morphology and crystallinity of the carbon, titanium-coated carbon and titanium thin films were investigated usingfield field effect emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscope (AFM), 4-point probe, solar simulator, respectively.