Study On Processing Technic And Fabrication Of CIGS Thin-Film Solar Cell

With no pollution and low cost, solar cell is the fastest developing clean energy and it can be used at any kind of geographical condition. For the past few years, thin-film solar cell has entered a new era of rapid developments. For the advantages of low cost, stable performance, high radioresistance, high absorptivity and efficiency, adjustable band gap of absorption material, copper indium gallium selenide (GIGS) thin film solar cell has caused wide concern by international photovoltaic industry.Firstly, the structure, operating principle, parameters and their influences on cell performance of CIGS solar cell are systematically discussed. The industrial manufacture of CIGS is mainly based on co-evaporation or post-selenization techniques, which have relatively high complexity and long manufacturing cycle. As an innovation to CIGS fabricating, we used the approach of RF magnetron sputtering, which is much more proficient in thin film preparation, to gain CIGS absorption layer. We set up a series of single-layer experiments for Mo back contact, CIGS absorption layer, CdS buffer layer and ZnO-ZAO window layer. Through the testing results of Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrum(EDS), X-Ray Diffraction(XRD) and ultraviolet spectrophotometer, we tried to investigate the influences of fabricating parameters such as sputtering pressure, substrate temperature, annealing temperature and solution concentration on thin film properties which include microstructure, crystallization, photovoltaic properties, transmission spectra and electric resistivity, so we could optimize fabricating parameters and prepare thin films that would meet the needs of high efficiency CIGS solar cell.It was testified that Mo back contact prepared by double-layer sputtering has good combining with glass substrate and relatively low electric resistivity. Bonding force between CIGS and Mo can be improved by heating substrate while sputtering, anneal treatment can improve crystallization and reduce electric resistivity of CIGS film. By optimizing solution concentration in chemical bath deposition of CdS, buffer layer which is relatively neat and homogeneous was gained and samples of CdS thin film has high transmissivity toward light when wavelength is above 580nm. Preliminary study about using RF magnetron sputtering to prepare CdS film has also been done. Through sputtering approach, ZnO and ZAO thin film which have high transmissivity in visible region was prepared. By increasing Ar pressure, electric resistivity at edge of ZAO thin film was reduced and optical band gap was widened. By optimizing and integrating single-layer fabricating process, we prepared CIGS solar cell with 2.14% efficiency.