Properties of Cu(In,Ga,Al)Se2 thin films fabricated by pulsed laser deposition

Cu(In,Ga,Al)Se2 (CIGAS) thin films were investigated as an alternative absorber layer to Cu(In,Ga)Se2 (CIGS). CIGAS thin films were prepared by pulsed laser deposition on SiO2/Si(100) and glass substrates at 150 °C with different Al contents. The compositions of all films were measured by electron probe micro-analyzer. X-ray diffraction studies indicate that all the films are oriented along the [112] direction and that the (112) peak shifts to higher 2θ value with increasing Al content. Scanning electron microscopy images show that dense and well-defined grains are formed as Al is incorporated into CIGS. Atomic force microscopy images indicate that the grain sizes and the roughness of the thin films decrease with increasing Al content. The bandgap of CIGAS thin films was determined from the optical spectra and was found to increase with increasing Al content.