Abstract
Thin film Si solar cells on inexpensive foreign substrates have attracted much attention in recent years because bulk Si based solar cells consume a lot of Si wafers which is the main contribution of high cost in the technology. The most mature Si thin film solar cells are the structures based on amorphous Si (a-Si:H) and microcrystalline Si (μc-Si:H). Aluminum induced crystallization (AIC) is one of another promising technology for fabricating pc-Si since its heat treatment temperature is comparably low (~400℃) and duration is fair. Solar cells based on AIC technology have reached the highest efficiency of 8% demonstrated by IMEC. Higher efficiency is difficult to reach due to the presence of intragrain defects which is an intrinsic defect of AIC. Altering cell structures may be one of the solutions to reach higher efficiency. In this thesis, we study the fabrication of high temperature back contact on full back area of cells rather than point contact to increase efficiency by lowering contact resistance between semiconductor and electrode. Our approach also increases area for incident light per unit cell. Nickel aluminide( NiAl ) is one of the candidates because of its low resistivity (~1E-5Ωcm) and high melting point (1638℃) which can sustain high temperature of epitaxy process for Si thickening. On the other hand, nickel aluminide do not react with pc-Si to form nickel silicide since Ni-Al bonding is more preffered than Ni-Si bonding. In this thesis， AIC and Ni/Al multilayer structures was deposited by RF-sputtering process then is annealed to proceed chemical reaction in order to form seed layer, pc-Si film and bottom electrode, NiAl, which has 100nm and 500nm in thickness, respectively. XRD was using for phase indenfication for NiAl. Microstructure of the films were explored by TEM. TLM (transfer length model) was applied to measure contact resistance, and junction characters were checked by I-V characteristics. The grain size of pc-Si film can achieve about 700nm, and the specific contact resistivity can be lower than 1mΩ∙cm^2.