Copper zinc tin sulfur solar cell materials

Copper Zinc Tin sulfur selenium cu2ZnSnSXSE4-X (CZTSSe) is a new generation of light absorption layer material for thin film solar cells.  The material has similar crystal structure and material properties to copper indium gallium selenium CuInXGa1-XSe2 (CIGS), which is currently outstanding in the field of thin film solar cells.  Copper, Zinc, tin, sulfur and selenium have high light absorption coefficient (greater than 104cm-1), adjustable band gap (1.0-1.5eV) and good photodepletion resistance. Moreover, the composition elements are abundant in the Earth, safe and non-toxic, which are very suitable for the development of high efficiency, cheap and stable performance of solar cells.  

The advantages of Copper Zinc Tin sulfur

In the preparation of copper, zinc, tin, sulfur and selenium materials, there is a high temperature selenization step, which is to partially replace sulfur element with selenium element and make grain grow up.  This step results in the formation of an interface layer between the absorption layer and the molybdenum electrode of Molybdenum sulfide selenide (Mo (S, Se) 2).  Appropriate thickness of molybdenum sulfide selenide can form ohmic contact with the absorption layer, and improve the adhesion between the absorption layer and the substrate, which is beneficial to the device.  However, if the moSE layer is too thick, the carrier transport will be hindered and the series resistance of the device will be increased, which is not good for the device performance.  In addition, under high temperature conditions, the copper, zinc, tin, sulfur and Selenium absorption layer may react with the molybdenum base, so that the decomposition of copper, zinc, tin, sulfur and selenium produces a secondary phase, which is also very adverse to the battery performance.  

Therefore, a back interface modification method is urgently needed to effectively prevent the formation of molybdenum sulfide selenide and the decomposition of cu, Zn, Sn, s - Se phase at the interface during high temperature selenization.