Study On Preparation Of Cu（InGa）Se₂Thin-film Solar Cell

Solar cell as a new type of clean energy is one of primary energy sources in future. Si solar cell currently is still dominated on the market, CIGS thin-film solar cell is regarded as low cost, high conversion efficiency and prominent stability solar energy devices. With resources and environment requirement, the market of CIGS thin-film solar cell is inevitable. The highest conversion efficiency about19.9%of CIGS solar cells have been produced using the mufti-stage co-evaporation technique. The method of Sputtering and selenium can easily control the process and suit to industrial production. At present, conversion efficiency of the foreign solar cell is generally12-13%, our research just start, and our technical level is far behind.In this dissertation, one simple, reliable and reproductive technology was developed for CIGS solar cells by selenization of sputtering alloy precursors. Firstly,1.Oμm thick Mo layers were deposited by DC-magnetron sputtering on stainless steel sheet. The residual stresses were minimized by using two-layer structure and changing the working pressure. Next,700nm-thick CuInGa precursors were deposited onto Mo-coated glass substrates by sputtering with CuInGa alloy target. A reproducible and easily scalable two-step selenization process of CuInGa layers was developed to form high quality CIGS absorbing layers. High-quality GIGS absorbers have been former by selenization of CuInGa precursors in a partially closed graphite container using selenium pellets, avoiding the generation of toxic H2Se gas. High-quality CIGS absorbers firstly stay for30minutes at low temperature, then were insulated for25minutes at high temperature. The deposited CIGS absorbers exhibited a single phase chalcopyrite strctuction with a preferential orientation in the (112) direction. These layers were uniform, and grain pack tightly. CdS window layers were prepared by Chemical bath deposition and Vacuum evaporation. Analysing and comparing CdS thin films prepared by two methods, the transmittance of CdS thin films prepared by vacuum evaporation deposition above the CdS thin films prepared by Chemical bath deposition. Finally, Al electrode of a certain thickness was prepared by DC-magnetron sputtering, then CIGS thin-film solar cells were prepared completely. The solar cells have a certain open-circuit voltage aboat30-40mv by testing the device performance. The whole technology of CIGS cells is simple, economical, and without using of toxic gases. It could easily be scaled up or integrated into a commercial process.