The crystallisation of Cu2ZnSnS4 thin film solar cell absorbers from co electroplated Cu Zn Sn precursors

The best CZTS solar cell so far was produced by co sputtering continued with vapour phase sulphurization method. Efficiencies of up to 5.74 were reached by Katagiri et al. The one step electrochemical deposition of copper, zinc, tin and subsequent sulfurization is an alternative fabrication technique for the production of Cu2ZnSnS4 based thin film solar cells. A kesterite based solar cell size 0.5 cm2 with a conversion efficiency of 3.4 AM1.5 was produced by vapour phase sulfurization of co electroplated Cu Zn Sn films. We report on results of in situ X ray diffraction XRD experiments during crystallisation of kesterite thin films from electrochemically co deposited metal films. The kesterite crystallisation is completed by the solid state reaction of Cu2SnS3 and ZnS. The measurements show two different reaction paths depending on the metal ratios in the as deposited films. In copper rich metal films Cu3Sn and CuZn were found after electrodeposition. In copper poor or near stoichiometric precursors additional Cu6Sn5 and Sn phases were detected. The formation mechanism of Cu2SnS3 involves the binary sulphides Cu2 xS and SnS2 in the absence of the binary precursor phase Cu6Sn5. The presence of Cu6Sn5 leads to a preferred formation of Cu2SnS3 via the reaction educts Cu2 xS in the presence of a SnS2 Cu melt. The melt phase may be advantageous in crystallising the kesterite, leading to enhanced grain growth in the presence of a liquid phas

Cu2ZnSnS4 thin film solar cells from electroplated precursors Novel low cost perspective

Abstract Thin film solar cells based on Cu2ZnSnS4 CZTS absorbers were fabricated successfully by solid state reaction in H2S atmosphere of electrodeposited Cu Zn Sn precursors. These ternary alloys were deposited in one step from a cyanide free alkaline electrolyte containing Cu II , Zn II and Sn IV metal salts on Mo coated glass substrates. The solar cell was completed by a chemical bath deposited CdS buffer layer and a sputtered i ZnO ZnO Al bilayer. The best solar cell performance was obtained with Cu poor samples. A total area 0.5 cm2 efficiency of 3.4 is achieved Voc 563 mV, jsc 14.8 mA cm2, FF 41 with a maximum quantum efficiency QE of 80 . The estimated band gap energy from the QE measurements is about 1.54 eV. Electron backscatter diffraction maps of cross section samples revealed CZTS grain sizes of up to 10 m. Elemental distribution maps of the CZTS absorber show Zn rich precipitates, probably ZnS, and a Zn poor region, presumably Cu2SnS3, close to the interface Mo CZTS. Keywords Electroplating; Cu2ZnSnS4; Solar cells; Cu poo