Toward Phase Pure CZTS Film-Based Solar Cell Prepared by the One-Step Hydrothermal Method: Influence of Copper Concentration

Abstract

Herein, the first paper for preparing Cu2ZnSnS4 film using EDTA as a complex agent by one-step hydrothermal method. The efficient Molybdenum oxide (MoO3) layer was also grown by the same step as preparing the Cu2ZnSnS4 film. The effects of different copper concentrations on the structural, optical, and electrical properties were studied. X-ray diffraction and Raman analyses confirmed the formation of polycrystalline kesterite phase Cu2ZnSnS4 films with preferred orientation along (112) plane and showed that structure property alters with copper concentration: at lower copper concentration single kesterite phase Cu2ZnSnS4 was formed, while with increasing copper concentration kesterite Cu2ZnSnS4 and secondary phases were formed. Field emission scanning electron microscopy revealed a mixture of micro-flower and a thin network of nanoflakes morphology. In addition, it showed as copper concentration changes the grain size of micro-flower and thickness of flakes change. UV-visible analysis showed high and broad absorbance spectra with high absorption coefficient values of more than 104 cm−1 in visible and infrared regions.also, predicted the band gap of single-phase Cu2ZnSnS4 film equal to 1.4 eV. Photoluminescence analysis demonstrated a single emission peak located at 1.55 eV which is quite near to the band gap of kesterite Cu2ZnSnS4. Hall measurement showed the single phase sample is a p-type semiconductor with a resistivity of 5 Ω cm, a charge carrier concentration of 7.5 × 1016 cm−3 and mobility of 16 cm2 Vs−1. Finally, a heterojunction solar cell was made with Mo foil/MoO3/CZTS/Zn0.35Cd0.65S/ZnO/Al configuration. A photovoltaic conversion efficiency of (2.17%) was attained under 100 mW cm−2 with an open-circuit voltage of (0.432) V, short-circuit current density of (13.4) mA cm−2 and a fill factor of (37.5%).