Development of Advanced Thin Film Photovoltaic Device using Chalcopyrite Semiconductor

为了使光伏发电系统实用化，开发低成本、高效率的太阳能电池是一个重要的课题。本研究以黄铜矿半导体为活性层的太阳电池为研究对象。由于光吸收系数大，该半导体有望提供低成本器件，并且由于带隙可调节到理论最佳值，该半导体有望提供高效率器件。本研究的目的是开发低成本、高效率的下一代薄膜太阳能电池。采用In/CuIn（Ga）Se前驱体在Mo/钠钙玻璃衬底上，在Se和S混合气氛下晶化制备了Cu（In，Ga）（S，Se）2薄膜。在Se气氛下，对CuInSe/CuGaSe叠层前驱体进行热处理，制备了Cu（In，Ga）Se_2薄膜。采用这种方法，得到了具有黄铜矿结构、成分和带隙可调的晶化薄膜。通过对CdS薄膜的结晶度、电学性能和光学特性的研究，探讨了溶液浓度和退火对CdS薄膜结晶度、电学性能和光学性能的影响。特别是，太阳能电池的性能迅速提高形成后的退火。研究了氧引入效应和衬底位置对溅射法制备i-ZnO薄膜的影响。向溅射气体中引入氧气对于获得更高的电阻率是有效的。采用射频磁控溅射法制备了离轴结构的n-ZnO薄膜，并对其进行了退火处理，以降低其电阻率。其值随退火温度的升高而降低。制作了太阳能电池，并研究了效率等的变化。通过在添加了S的Se气氛中结晶证实了太阳能电池的开路电压的快速提高。

It is an important issue to develop a low cost and high efficient solar cel1 in order to make photovoltaic system put in practical use. In this research, the solar cel1 with chalcopyrite semiconductor as an activity layer was investigated. This semiconductor is expectable to provide a low cost device because the optical absorption coefficient is large, and a high efficient device because the band gap is adjustable to the theoretical optimal value. In this research, the purpose is to develop a next-generation thin film solar cell with low cost and high efficiency. Cu(In, Ga) (S, Se)_2 thin films were produced by crystallizing In/CuIn(Ga)Se precursor on Mo/soda lime glass substrate in Se and S mixing atmosphere. Moreover, Cu(In, Ga)Se_2 thin films were produced by thermal treatment of stacked CuInSe/CuGaSe precursor in Se atmosphere. By using this method, the crystallized thin films, which have a chalcopyrite structure and can regulate their composition and band gap, were obtained. The effects of the solution concentration and the annealing after the formation of CdS thin films by chemical bath deposition from iodine compounds were evaluated by the crystallinity, the electrical property and the optical characteristic. Especially, the solar cell performance was rapidly improved by the annealing after formation. The influence of the oxygen introduction effect and the substrate position were evaluated for i-ZnO thin films prepared by sputtering. It was effective to have introduced oxygen into the sputtering gas for a higher resistivity. The annealing of n-ZnO prepared by rf magnetron sputtering with off-axis configuration was carried out to reduce the resistivity. Its value decreased with increasing the annealing temperature. The solar celIs were produced and the change of the efficiency etc. was investigated. The rapid improvement in the open circuit voltage of a solar cell was confirmed by crystallizing in Se atmosphere which added S.