Abstract
The development of solar cells has attracted much attention because of the significance of energy crisis. Cu-III-VI2 thin film solar cells exhibit advantages such as high efficiency, low cost, light weight, flexible and longevity, which are positive for thin film solar cell development. The main technologies suitable for mass-production of large area CIGS solar cells are sputtering and post-selenization (or sulfurization), such as Solar Frontier of Japan and Taiwan Semiconductor Manufacturing Company (TSMC) of Taiwan. However, the mass-production technology of large area CIGS solar cells is quite difficult as follows: First, the process of selenization (toxic H2Se gas) is harmful for human body and environment respectively. Second, the fabrication of CIGS film with large area and high uniformity is difficult. The current encountering problem of mass-production technology of CI(G)S solar cells is that there is no effectively stable and environmental selenization process. Therefore, this thesis has proposed innovative hydrogen-plasma selenization to develop large-scale ternary CuIn(Ga)Se2 solar cells with mass-production value. The detailed technologies include: (1) the usage of Se vapor to replace toxic H2Se gas to form high quality hetero-junction and eco- environmental process. Then, passivated defects by adding H2 in carrier gas and lengthen the diffusion length of metal Se vapor to acquire CI(G)S film with large area uniformity and high crystallinity. (2) Using stacking technology achieve the purpose of the band gap engineering. (3) This thesis also introduces high density plasma technology to activate Se element, increase reactivity, enhance film compactness, uniformity, crystallinity, and good element composition ratio. This can further reduce the process time and temperature and fabricate CI(G)S solar cells with mass-production value and even on flexible substrate. Furthermore, this thesis also modified (1) substrate clean process and following modified high quality Mo bottom electrode with low resistivity and well adhesion with glass substrate, (2) uniform and stoichiometric large scale n-type CdS buffer layer process, (3) high resistive ZnO layer for uniform VOC distribution as well as (4) transparent conductive ITO layer with extremely low sheet resistance and high transmittance. Finally, the large-area, high-uniformity and high conversion efficiency CI(G)S solar panel is realized. So far, it has achieved high uniformity CIGS solar panels with the highest conversion efficiency of over 14.7 % and over 11.4 % while substrate temperature is decreased as low as 450 oC. Moreover, PESVS enabled low temperature processed flexible CIGS solar panel exhibit 6.8 % conversion efficiency without Na ions addition.