Efficiency Improvement of Flexible Cu2ZnSn(S,Se)4 Solar Cells by Window Layer Interface Engineering

Flexible Cu2ZnSn(S,Se)(4) (CZTSSe) solar cells have wide application prospects. N-type window layers and contact among the layers have an important effect on the properties of flexible CZTSSe solar cells. Here, we present a modified structure for flexible CZTSSe solar cells with window layers (CdS/ITO) instead of the traditional window layers (CdS/ZnO/ITO) for higher performance and lower cost. The flexible CZTSSe device realizes 9.2% efficiency with an improved fill factor (FF) from 57.7 to 63.6%. Systematic physical measurements show that the increase in FF comes from a significant decrease in series resistance (R-s). To enhance the antireflective function of the window layers, we introduce MgF2 antireflection coatings on the surfaces of solar cells. The average J(sc) of devices is significantly enhanced 6% due to the antireflective effect. A champion device achieves an efficiency of 9.7% with the highest FF of 64.0% in the flexible CZTSSe solar cells. The present investigation will provide a new strategy for the development of flexible CZTSSe solar cells.

Automated summary

By utilizing a modified window layer structure (S/CdS/ITO), the performance of flexible CZTSSe solar cells has been enhanced, achieving an efficiency of 9.2%. The introduction of MgF2 antireflection coatings leads to a 6% improvement in the average J(sc) of the devices, with a champion device reaching an efficiency of 9.7%.