Development of a Selective Chemical Etch To Improve the Conversion Efficiency of Zn-Rich Cu₂ZnSnS₄ Solar Cells

Abstract

Improvement of the efficiency of Cu(2)ZnSnS(4) (CZTS)-based solar cells requires the development of specific procedures to remove or avoid the formation of detrimental secondary phases. The presence of these phases is favored by the Zn-rich and Cu-poor conditions that are required to obtain device-grade layers. We have developed a selective chemical etching process based on the use of hydrochloric acid solutions to remove Zn-rich secondary phases from the CZTS film surface, which are partly responsible for the deterioration of the series resistance of the cells and, as a consequence, the conversion efficiency. Using this approach, we have obtained CZTS-based devices with 5.2% efficiency, which is nearly twice that of the devices we have prepared without this etching process.

The importance of back contact modification in Cu2ZnSnSe4 solar cells: The role of a thin MoO2 layer

“…It seems clear that to improve CZTSSe devices changes in the processing conditions to maximize V OC must be performed, with the bulk and interfaces of the material as paramount working areas. Whereas chemical etchings have proved to be an important tool to modify the properties of the p-n junction, and therefore improve V OC among other parameters, changing the back contact interface led as well to significant improvements [15][16][17][18][19][20][21]. The present work is devoted to the modification of the properties of the Mo/CZTSe interface by using different Mo configurations (monolayer, bi-layer and tri-layer) and an innovative intermediate ultrathin MoO 2 layer in CZTSe solar cells.…”

Multiwavelength excitation Raman scattering study of polycrystalline kesterite Cu2ZnSnS4 thin films

“…To remove this secondary phase from the surface of the films, a selective chemical etching for ZnS has been performed with a HCl solution. 24 After etching with this solution, the composition ratios change to values closer to a stoichiometric composition (Cu/(Zn þ Sn) ¼ 0.96 and Zn/Sn ¼ 1.09). The spectra presented in this letter correspond to the as-etched sample.…”

Electrodeposition and selenization of brass/tin/germanium multilayers for Cu2Zn(Sn1-xGex)Se4 thin film photovoltaic devices

“…The effect of the removal of potentially detrimental secondary phases on the PEC properties of the film has also been investigated. For this purpose, consecutive surface etching treatments have been performed with potassium cyanide and hydrochloric acid solutions, which are known to remove secondary phases from the surface of the absorber material [50,51]. Fig.…”