Preparation And Properties Of Absorb Layer For CIGS Thin Film Solar Cells

Copper indium gallium selenide (CIGS) thin film solar cells has the advantage ofhigh conversion efficiency, low cost, suitability for mass production, etc. Its absorptionlayer belongs toⅠ-Ⅲ-Ⅵ semiconductor material with tunable band gap (1.04-1.65eV)and high absorption coefficient (~105cm-1). In this work, we try to prepare absorberlayer CIGS thin film by DC magnetron sputtering CIGS quaternary target. Theinfluence of the sputtering parameters and annealing process have been investigated onthe structure, morphology, composition and performance of CIGS film.Mo back contact layers are deposited by DC magnetron sputtering. And itsstructure, morphology and electric properties are characterized. It is shown that theprepared Mo film has the dense microstructure, good crystallinity, about1μm thickness,the sheet resistance of about0.12Ω/sq, which meets the requirements ofhigh-performance devices.CIGS absorber layers are deposited by DC magnetron sputtering. It is shown thatsubstrate temperature plays a decisive role on the crystallinity of CIGS thin film. As thesubstrate temperature increases, the crystallinity of the film is improved, the grain sizeincreases, while the resistivity decreases, the carrier concentration increase. However,when the substrate temperature is too high, the film may occur phase separationphenomenon. Studies have shown that working pressure also has a significant impact onCIGS thin films. As the working pressure is gradually increased, the film has poorercrystallinity and less compactness. In addition, with the increase of working pressure,the carrier concentration decreases firstly, and then increases, while the variation of thecarrier mobility is the opposite. Resistivity of the film is trending downward, which isinfluenced by the carrier concentration, mobility and Cu2-xSe secondary phase Theband gap CIGS thin film is between1.6eV and1.7eV and increases with the increaseof [Ga]/[Ga+In].CIGS thin films are annealed by rapid thermal annealing process. It is shown thatas the annealing temperature increases, the crystallinity of the film becomes better,(112)fiber texture gradually forms, and most of the residual stress is released; when theannealing temperature is too high, Mo layer and CIGS layer will separate, and a largeamount of impurity phase will appear. Furthermore, after the annealing treatment, the carrier concentration of CIGS thin film increases, while the resistivity decreases; whenthe annealing temperature reaches550°C, the resistivity of the film is greatly increased,and the carrier concentration is relatively reduced.