9.4% efficient Cu2ZnSnSe4 solar cells from co-sputtered elemental metal precursor and rapid thermal annealing

We present a fast fabrication route for Cu2ZnSnSe4 (CZTSe) kesterite absorbers using co-sputtering of elemental metal precursor followed by rapid thermal annealing with selenium capping layers. The formation of secondary phases at the absorber surface can be reduced, making a specific etching routine redundant. Starting from a homogenous metal precursor with Se capping layer, a short annealing time of 5 min at 550 °C is sufficient to achieve a fully crystallized kesterite absorber. Selenium capping layers with thickness at least twice the precursor thickness yield homogenous absorbers on 5 × 5 cm2 samples but also promote the formation of ZnSe. By reducing the Se layer thickness an enhanced grain growth and reduction of secondary phases can be achieved, which finally yields efficiencies up to 9.4%.