Device Characteristics of CZTSSe Thin‐Film Solar Cells with 12.6% Efficiency

The thin-fi lm photovoltaic material Cu 2 ZnSnS x Se 4– x (CZTSSe) has drawn world-wide attention due to its outstanding performance and earth-abundant composition. Until recently, [ 1 ] stateof-the-art CZTSSe thin-fi lm solar cells were limited to 11.1% power conversion effi ciency (PCE), with these performance levels being achieved via a hydrazine slurry approach. [ 2 ] Other vacuumand non-vacuum-based deposition techniques have also been successful in fabricating CZTSSe solar cells with PCE above 8%. [ 3,4 ] However, even record devices with PCE of 11% are still far below the physical limit, known as the ShockleyQueisser (SQ) limit, of about 31% effi ciency under terrestrial conditions. [ 5 ]