Silver-Doped Cu2(Sn,Ge)S3 Solar Cells

Herein, the usefulness of silver (Ag)-doping into Cu-2(Sn,Ge)S-3 (CTGS) solar cells is demonstrated. From an observation via a field emission scanning electron microscope, grain growth promotion of the CTGS thin films by Ag-doping is revealed. It is found that undesirable defects are suppressed by an adequate Ag-dopant amount, resulting in reduced nonradiative recombination in photoluminescence spectra for the Ag-doped CTGS films. For the CTGS solar cell devices, Ag-doping into the CTGS absorbers mainly improves the short-circuit current density and open-circuit voltage. Finally, 3.2%-efficient Ag-doped CTGS solar cell is obtained at [Ag]/([Ag] + [Cu]) ratio of 0.05. It is believed that these findings will help to realize the highest efficiency for the CTGS solar cells.