Growth and characterization of Cu2ZnSnSe4 (CZTSe) thin films by sputtering of binary selenides and its selenization

Abstract

Copper Zinc Tin Selenide (CZTSe) thin film solar cell is the most promising source of energy production of the future. It is free from rare and toxic elements which are used in other thin films solar cells like Cadmium Telluride (CdTe) and Copper Indium Gallium Selenide (CIGS). CZTSe is basically a replacement for high performing CIGS thin film solar cells. Indium and Gallium are rare in Earth’s crust which is the major factor of the price increase. However, replacing Indium and Gallium with Zinc and Tin will give the benefit of huge cost reduction because both the elements are present in abundance on Earth. CZTSe thin film solar cells are relatively new born as compared to CIGS thin film solar cells. CZTSe Research was started on these solar cells in late 1990s, almost 35 to 40 years later than CIGS research. But the research in this area is growing and many photovoltaic research groups have taken interest in development of this low cost alternative of permanent energy generation source. There are two major issues making serious hurdles in the progress of CZTSe thin film solar cells, which are a) tin loss during annealing and b) poor adhesion at the interface of absorber layer and the molybdenum. In this study, these two issues has been addressed by using binary selenides precursor sources and annealing in close space sublimation equipment and thermal evaporator, both having selenium atmosphere. In the beginning, six types of stacking orders were prepared to have check which stacking order is more suitable to address the issue mentioned above with good morphology and grain growth. These six stacking orders were prepared with reference to the tin selenide on the soda lime glass substrate. In the first stacking order (A), tin selenide was kept at the top and followed by copper selenide and zinc selenide. Second stacking order (B) also had tin selenide at the top but followed by zinc selenide and copper selenide. Third stacking order (C) had zinc selenide ...