Cauliflower Cu2ZnSnS4:Na film prepared by single-pot hydrothermal approach for photovoltaic application: impact of NaOH additive

Cu 2 ZnSnS 4 :Na promising quaternary chalcogenide material was deposited using a single-step hydrothermal method via EDTA as a complex agent. Various NaOH additives were studied to see how they affected the crystallographic, microstructure, optical, and electrical properties. The formation of polycrystalline kesterite Cu 2 ZnSnS 4 :Na films with a preferred orientation along (112) plane was shown by X-ray diffraction (XRD) and Raman analyses. These analyses also revealed that the structure's properties vary with NaOH additive: single-phase Cu 2 ZnSnS 4 :Na was formed at higher NaOH value and the secondary phase was formed within CZTS at lower NaOH values. Surface morphology changes from flake-flower to cauliflower, according to field emission scanning electron microscopy. Also, EDS peaks confirm the presence of Cu, Zn, Sn, Na, and S. UV–visible analysis indicates that all samples had high and wide absorbance spectra with absorption coefficients greater than 10 4 cm −1 in the (200–1000) nm range. Additionally, a 1.5 eV band gap for the single-phase Cu 2 ZnSnS 4 :Na film was estimated. For single-phase Cu 2 ZnSnS 4 :Na, photoluminescence revealed a peak at 1.47 eV, the energy value is in close proximity to the optical band gap of the ideal compound Cu 2 ZnSnS 4 :Na.The Hall measurement indicates the pure sample has p-type conductivity with a charge carrier concentration of 6 × 10 17 cm −3 . The resistivity of pure CZTS:Na and mobility were 1 Ω.cm and 10.4 cm 2 .Vs −1 . Finally, the configuration of Mo foil/MoO 3 /CZTS:Na /Zn 0.35 Cd 0.65 S/ZnO/Al was used to produce a heterojunction solar cell. Under 100 mW/cm 2 , an open circuit voltage of (0.415) V, a short circuit current density of (14.3) mA cm- 2 , a fill factor of (38%), and the effectiveness of photovoltaic cells of (2.26%) were achieved. Graphical abstract