Effects of substrate temperature on the structural and electrical properties of Cu(In,Ga)Se-2 thin films

Polycrystalline Cu(In,Ga)Se-2 (CIGS) thin films were deposited onto soda-lime glass substrates using the three-stage process at the substrate temperature (T-sub) varying from 350 to 550 degrees C. The effect of Tub on the structural and electrical properties of CIGS films has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect measurement. We found that the surface roughness, constituent phases, film morphologies, resistivity (rho) and carrier concentration (N-P) of as-grown CIGS films indicated different change trends with increase in T-sub. The higher Tsub gives smooth surface, large grain size and single-phase CIGS films. The values of N-P and rho have two demarcated regions at T-sub of 380 and 450 degrees C. At lower T-sub of 380 degrees C, larger N-P and lower rho were dominated by the existence of secondary-phase CuxSe with lower resistivity. In the case of 450 degrees C, the obvious changes in NP and p can be attributed to the sufficient Na incorporation diffused from the glass substrate. Finally, the correlation of cell parameters with T-sub was analyzed. (C) 2008 Elsevier B.V. All rights reserved.