Re-Crystallization of CZTS Solar Cell Materials Prepared by Galvanostat Electro-Deposition

Abstract

Quaternary Cu2ZnSnS4 (CZTS) films were successfully obtained on Mo/(soda lime glass) substrates by one-step electro-deposition. The process was more efficient than other electro-deposit processes. Electrolytic aqueous was prepared using CuSO4, ZnSO4, SnSO4 and Na2S2O3 mixing solution. A galvanostat was applied for the deposition using a double-electrode scheme. The as-deposited CZTS was re-crystallized and then treated with sulfurization. Kesterite-type CZTS with nano-particle sizes ~17 nm on Mo/SLG were identified by x-ray diffraction (XRD). Different CZTS granules with sizes of 0.5 ~ 5 um were aggregated on surface morphologies as analyzed by scanning electron microscopy (SEM). The CZTS crystallinity was improved through the re-crystallization process. The absorption coefficients are over 1x104 cm-1 in the visible range. The spectrum of square absorption coefficient versus photon energy spectra depicts that the obtained CZTS has a band gap energy of ~1.25 eV. The optical band gap depicts that the obtained CZTS is suitable for thin film solar cell application.