We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stacked structure and described the phenomenon of Zn elemental volatilization using the MZCT stacked structure.

Using an appropriate SeS2/Se weight ratio, band gap grading was realized. By increasing the value of VOC through band gap grading in the depletion region, a record VOC deficit of 0.576 V and an efficiency of 12.3% were obtained.

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In this study, we investigated the effect of the stacking order of metal precursors on the formation of volume defects, such as blisters and nanopores, in CZTSSe thin-film solar cells. We fabricated CZTSSe thin films using three types of metalprecursor combinations, namely, Zn/Cu/Sn/Mo, Cu/Zn/Sn/Mo, and Sn/Cu/Zn/Mo, and studied the blister formation. The blisterformation mechanism was based on the delamination model, taking into consideration the compressive stress and adhesion properties. A compressive stress could be induced during the preferential formation of a ZnSSe shell. Under this stress, the adhesion between the ZnSSe film and the Mo substrate could be maintained by the surface tension of a metallic liquid phase with good wettability, or by the functioning of ZnSSe pillars as anchors, depending on the type of metal precursor used. Additionally, the nanopore formation near the back-contact side was found to be induced by the columnar microstructure of the metal precursor with the Cu/Zn/Mo stacking order and its dezincification. Based on the two volume-defect-formation mechanisms proposed herein, further development of volume-defect-formation suppression technology is expected to be made.

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