Gas-pressure assisted sintering of copper indium gallium selenide thin films

Defects, such as cracks, porous structure, small grains that easily occur in the fabrication of copper indium gallium selenide (CIGS) thin film absorbers using non-vacuum process have been the major obstacle to practical application of this technology so far. A gas-pressure assisted sintering process has been developed to achieve dense, crack-free, large-grained CIGS films. The gas-pressure assisted sintering effects on the microstructure, crystalline, and electric properties were investigated by scanning electron microscopy, X-ray diffraction, and Hall-effect analyzer. A uniform microstructure with a large grain size and small amount of isolated residual pores and good electric properties can be obtained by pre-sintering at 500°C under 6 bar N₂ overpressure and then annealing at 500°C for 20 minutes under a selenium atmosphere.