Characterization of a CZTS thin film solar cell grown by sputtering method

• 6.2% CZTS/CdS solar cell without AR coating.
• QE modeling shows less than half the thickness of the CZTS layer contributes to photocurrent.
• Detailed characterization of the CZTS cell properties.

We report the performance of Cu2ZnSnS4 (CZTS) thin film solar cell that showed efficiency in the range of 6.2% without an anti-reflection coating. Initially, the CZTS precursor film was co-sputtered using three different targets; copper (Cu), tin sulfide (SnS) and zinc sulfide (ZnS). The Cu target was subjected to DC power, and RF power was used for the SnS and ZnS targets. The as-grown CZTS film was sulfurized in a H2S/N2 environment at 525 °C, which re-crystalized the film with grain sizes in the range of 1 μm. Cadmium sulfide (CdS) was used as the n-type layer. Current–voltage (I–V), quantum efficiency (QE) and capacitance–voltage (C–V) measurements were used to characterize the cell device. The modeling and analysis of QE and CV data showed that a significant portion of the CZTS layer did not contribute to the photo-generation. Optimizing CZTS phase purity, improving QE in the broader wavelength region, and increasing minority carrier lifetime are necessary steps to further improve CZTS device performance.