Effect of Substrate Temperature on the Physical Properties of ZnхSn1 – хSe Films for Thin-Film Solar Cells

Abstract

At the present time, 92% of the PV market is made using single crystal or polycrystalline wafer silicon. However, producing power with these cells remains expensive compared to conventional power generation. Thin film solar cells have been developed to reduce production costs, especially those based on cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Despite a number of successes in the development of thin film solar cells, some problems associated with the toxicity of cadmium and with the high cost of indium and gallium remain, which has prompted researchers to search for alternative materials for solar cells. Novel low cost and high efficiency zinc tin selenide (Zn_xSn_1 – xSe) thin film solar cells are without these drawbacks. However, there is no information in the literature about this new material. The samples of Zn_xSn_{1 – x}Se films were fabricated using the chemical molecular beam deposition (CMBD) method at atmospheric pressure in hydrogen flow. ZnSe and SnSe powders with 99.999% purity were used as precursors. The temperature of precursors varied in the range of 850–950°C. Films were deposited at substrate temperature of 500–600°C. Borosilicate glass was used as a substrate. The results showed that the composition of the samples changed toward ZnSe with the temperature of the substrate. The grain size of the samples increased from 2–5 μm to 15–17 μm at substrate temperatures of 500 and 550°C, respectively. At a substrate temperature of 600°C, the grain size decreased to 3–5 μm, which is possibly due to an increase in the ZnSe content. The X-ray diffraction pattern has shown that the samples have ZnSe, SnSe, Se, and Sn phases.