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 thestructural, electrical and optical properties of copper zinc tin selenide (CZTSe) absorber layer forthin film solar cells. The precursors were deposited sequentially on the soda lime glass substrate atroom temperature by DC magnetron sputtering. The precursors were selenized by annealing in anatmosphere containing selenium pellets and nitrogen gas. The structural, morphological, opticaland electrical properties were respectively characterized using X-Ray Diffractometer (XRD),atomic force microscopy (AFM), UV/VIS/NIR lambda 9/19 spectrophotometer, Hall Effectmeasurement system (HMS 3000) and a four point probe system. CZTSe samples made up ofthree 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 peakoriented along (112) plane at an angle of 2 ≈ 27.2°. Stack C was a best stacking order since it hadthe largest grain size 67 nm, highest carrier concentration 3.4  1020 cm–3 and the lowest sheetresistance of 6.4 /□. Also this film demonstrated higher average absorption coefficient of about6.84  104 cm–1. Furthermore, the films were observed to have a smooth surface and wellcompacted with average surface roughness of about 16 nm without voids.