An Insight Into Pure Ge Based Kesterite Synthesis

This work exhibits fascinating phenomena behind the synthesis of pure Ge kesterite revealed by means of XRD, Raman spectroscopy and by SEM. The absorber is prepared by a sequential sputtering and annealing process. Stopping the synthesis at different times we show that in the case of Cu2ZnGeSe4 the reaction proceeds via a vapor-liquid-solid phase reaction, thanks to the formation of Ge-Se liquid phases. Optimizing the synthesis process, we report a solar cell device with power conversion efficiency resulted in this study exceed the 6% (V-oc = 556 mV, FF = 59.6%, J(sc) = 19.6 mA/cm(2)).