Oxygen annealing and Zn/HCl etching effects on CZTS devices

CZTS films were air-annealed, etched to eliminate any SnO
₂
and ZnS at the CZTS surface, and finished as solar cells with CdS and ZnO. Although this did not improve device efficiencies, it did improve the short circuit current in the 200 °C-annealed and etched cells. A careful look at the EQE of several of these devices showed that, although these steps caused the CdS layer to grow thicker and reduce current collection from high-energy photons, the near-band gap EQE was enhanced, especially in etched devices.