Enhancement of efficiency in Cu₂ZnSnS₄ (CZTS) solar cells grown by sputtering

We report the cell performance of Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSnS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTS) thin film solar cell that showed efficiency in the range of 6 to 7 %. The absorber layer was grown by magnetron sputtering followed by annealing in a H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S/N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> environment. Initially, the CZTS film was co-sputtered with three different targets; copper (Cu), tin sulphide (SnS) and zinc sulphide (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 sulphurized in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S environment at around 510°C, which re-crystalized the film with larger grains. The quantum efficiency measurement showed internal quantum efficiency as high as 80% around 600 nm wavelength. A typical cell showed 610 mV open circuit voltage, 16 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> short-circuit current, and 6.2% efficiency.