Effects of Selenized DC Sputtered Precursor Stacking Orders on the Properties of Cu2ZnSnSe4 Absorber Layer for Thin Film Solar Cells

Abstract

This study investigated the effects of selenized DC sputtered precursor stacking orders on the structural, electrical and optical properties of copper zinc tin selenide (CZTSe) absorber layer for thin film solar cells. The precursors were deposited sequentially on the soda lime glass substrate at room temperature by DC magnetron sputtering. The precursors were selenized by annealing in an atmosphere containing selenium pellets and nitrogen gas. The structural, morphological, optical and electrical properties were respectively characterized using X-Ray Diffractometer (XRD), atomic force microscopy (AFM), UV/VIS/NIR lambda 9/19 spectrophotometer, Hall Effect measurement system (HMS 3000) and a four point probe system. CZTSe samples made up of three different stacking orders with configuration Mo/Cu/Zn/Sn (stack A), Mo/Cu/Sn/Zn (stack B) and Mo/Zn/Sn/Cu (stack C) were prepared. All the films showed kesterite peaks with major peak oriented along (112) plane at an angle of 2 ≈ 27.2°. Stack C was a best stacking order since it had the largest grain size 67 nm, highest carrier concentration 3.4   1020 cm–3 and the lowest sheet resistance of 6.4 /□. Also this film demonstrated higher average absorption coefficient of about 6.84   104 cm–1. Furthermore, the films were observed to have a smooth surface and well compacted with average surface roughness of about 16 nm without voids.