Investigation of selenization process of electrodeposited Cu–Zn–Sn precursor for Cu2ZnSnSe4 thin-film solar cells

• The thickness of MoSe2 of home-made Mo substrate was constant.
• Center of photoluminescence peak was dependent on Cu2ZnSnSe4 composition.
• Poor quality of Mo/Cu2ZnSnSe4 interface resulted in low shunt resistance.

In this study we present the investigation of Cu2ZnSnSe4 (CZTSe) absorber layers formed using electrochemical co-deposition in the stirred citrate solution. Two different Mo back contacts were tested to evaluate the formation of MoSe2 during selenization of electrodeposited Cu–Zn–Sn (CZT) precursor. Cleaved and focused ion beam made cross-sections of CZT/Mo and CZTSe/MoSe2/Mo layers and surface morphology of CZTSe were studied by scanning microscopy. The chemical composition was determined by x-ray energy dispersive and fluorescence spectroscopy, whereas phase composition was examined by x-ray diffraction and Raman spectroscopy. The formation of MoSe2 strongly depended on the microstructure of Mo and annealing conditions. Possible reasons for different selenization of Mo back contacts used were discussed. Photoluminescence (PL) measurements revealed that characteristics of CZTSe main PL peak were compositional dependent. The highest CZTSe solar cell efficiency obtained was 2.64%.