| Summary: | 碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 101 === Confronting with the problem of energy crisis, the renewable resources have received lots of attention from all over the world. Solar cell is one of the best choices which show a great deal of promise in replacing fossil fuels. In this field, CIGSe thin-film solar cells have been studied and used for a period of time. However, the rare elements, such as indium and gallium, used in CIGSe made its cost get increased. Therefore, low cost Cu2ZnSnSe4 is emerging to try taking the place of it.
In this study, we successfully fabricated CZTSe thin-film solar cell devices by sputtering method. The absorption layers were grown by DC sputtering in vacuum system using Cu-Zn-Sn targets with different compositions to deposit CZT precursors on Mo-coated soda-lime glass (SLG) substrates followed by different selenization conditions. The characterizations of thin films were analyzed by X-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM) epuipped with an energy dispersive X-ray spectrometer (EDS), and Hall measurement. Solar cells were then fabricated with the device stacks consisting of the following: SLG/Mo (DC, 700nm)/CZTSe (DC, 1μm)/CdS (CBD, 70nm)/i-ZnO (RF, 50nm)/ITO(RF, 400nm)/Ag
The performance of the device was then evaluated under the standard AM 1.5 illumination.
The results showed that CZTSe thin films which were made by a two-step selenization process at 600 ℃for 1 hr had grain size of 2 μm~6 μm. XRD and EDS analyses demonstrated that the films were single phase with the close component of Cu0.9ZnSnSe2.
Device made by target A contained Cu-poor CZTSe as an absorber. This device only got 1.61 % conversion efficiency. Device made by target B had the slightly Cu-rich component and it reached 2.95 % conversion efficiency. Device made by target C had the mobility of 38.2 cm2V-1s-1 and conductivity of 12.79 Ω-1cm-1 for its absorber layer. Its electrical properties are suitable for solar cells, which leads to the best conversion efficiency of 3.72 %. Device made by target D had the absorber with high carrier concentration of 9.63×1019 cm-3 and had its lower conversion efficiency of 2.38 % than that from target C.
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