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Keywords:

  • preferred orientation;
  • Fe diffusion;
  • CIGS thin film

ABSTRACT

The influences of process parameters and Fe diffusing into Cu(In,Ga)Se2 (CIGS) films on the orientation of CIGS absorbers grown on the stainless steel (SS) foils are investigated. The structural properties, morphology, and elemental profiles are characterized using X-ray diffraction, scanning electron microscopy, and second ion mass spectroscopy, respectively. The orientation of CIGS thin films on the SS substrates strongly depends on the texture of the (In,Ga)2Se3 precursor, determined by the substrate temperature at the first stage (Ts1) and the flux ratio of Se to (In + Ga). Among these factors, Ts1 is the prerequisite to achieve [300]-oriented IGS layer, which will yield [200]-oriented CIGS thin film in the later process. The results indicate that through the comparison of CIGS thin films on the Mo/SS substrates and on the Mo/ZnO/SS substrates and combined with simply calculation, Fe diffusing into the CIGS layer will hinder the growth of the CIGS grains along [112] orientation. The grazing-incidence X-ray diffraction results suggest that the surface of the [220]-textured CIGS thin film on the SS substrate still has [220] predominance, whereas the surface texture of the [220]-texture CIGS thin film on the Mo/soda-lime glass substrate became [112] predominant, which is due to the different compensation ability between Fe and Na elements. Finally, the relations between the device parameters and the degrees of the preferred orientation of CIGS absorbers are investigated. Copyright © 2012 John Wiley & Sons, Ltd.