Oscillating temperature selenization of Cu, Ga, In elemental layers in a Se vapour [CuGaInSe2 solar cells]

CuGa_0.3In_0.7Se₂ thin films have been grown by selenization of Cu, Ga, In elemental layers in a Se vapour by a novel method in which a first part of the film is prepared by making the substrate temperature to oscillate between 200-230°C and 480-550°C with a risetime of 1-2 minutes and cooling down time of 6-9 minutes. The film is completed by increasing the substrate temperature from 380°C to 480-500°C with a ramp of 1-2°C/min. X-ray spectra and scanning electron micrographs indicate that the films are monophasic and very well crystallized with a strong orientation along the (112) direction. CuGa_0.3In_0.7Se₂/CdS thin film solar cells made on both Corning 7059 or Soda Lime glass substrates exhibit an efficiency larger than 12%