Fabrication of solar cells based on $C{u}_{2}ZnSn{S}_4$ prepared from $C{u}_{2}Sn{S}_3$ synthesized using a novel chemical procedure

Abstract

Solar cells based on kesterite-type $C{u}_{2}ZnSn{S}_4$ (CZTS) thin films were fabricated using a chemical route to prepare the $CZTS$ films, consisting in sequential deposition of $C{u}_{2}Sn{S}_3$ (CTS) and $ZnS$ thin films followed by annealing at $550^{\circ }C$ in nitrogen atmosphere. The $CTS$ compound was prepared in a one-step process using a novel chemical procedure consisting of simultaneous precipitation of $C{u}_{2}S$ and $Sn{S}_2$ performed by diffusion membranes assisted $CBD$ (chemical bath deposition) technique. Diffusion membranes were used to optimize the kinetic growth through a moderate control of release of metal ions into the work solution. As the conditions for the formation in one step of the $C{u}_{2}Sn{S}_3$ compound have not yet been reported in literature, special emphasis was put on finding the parameters that allow growing the $C{u}_{2}Sn{S}_3$ thin films by simultaneous precipitation of $C{u}_{2}S$ and $Sn{S}_2$. For that, we propose a methodology that includes numerical solution of the equilibrium equations that were established through a study of the chemical equilibrium of the system $SnC{l}_2$, $N{a}_3{C}_6{H}_5{O}_7\cdot 2H2O$, $CuC{l}_2$ and $N{a}_2{S}_2{O}_3\cdot 5H_{2}O$. The formation of thin films of $CTS$ and $CZTS$ free of secondary phases grown with a stoichiometry close to that corresponding to the $C{u}_{2}Sn{S}_3$ and $C{u}_{2}ZnSn{S}_4$ phases, was verified through measurements of X-ray diffraction $(XRD)$ and Raman spectroscopy. Solar cell with an efficiency of $4.2$, short circuit current of $16.2mA/c{m}^2$ and open-circuit voltage of 0.49 V was obtained.

in Spanish