A study of microstructure and optical absorption properties of Cu(In,Ga,Al)Se2 powders

CuInxGayAl1-x-ySe2 powders were prepared using a solvothermal reaction technique in ethylenediamine at 290°C for 20 hours. The microstructure and optical absorption properties of the powders were investigated by XRD, SEM, TEM, XPS and UV-Vis-NIR spectra. The results indicated that the Al atom was successfully incorporated into the CuInxGa1-xSe2 lattices, and Al doping had a significant effect on the microstructure, especially at the (112) crystal orientation. It was found that the peak of (112) shifted obviously to higher 2θ values with the increasing aluminum content. Transmission electron microscope observation revealed that the size of the CuInxGayAl1-x-ySe2 nanoparticles could be adjusted by varying the stoichiometric ratio of the In, Ga and Al, and the proper Al incorporation could reduce the density of the stacking faults and nanotwins in the CuInxGayAl1-x-ySe2 materials. XRD analysis indicated that the Al incorporation could effectively substitute In and Ga atoms. Finally, the band gap was obtained by UV-Vis-NIR spectra, and the results implied that the optical absorption value decreased and optical band gap increased significantly with the incorporation of Al, and it is close to the optimal band gap (1.37 eV) of solar cells when the stoichiometric ratio of the Al was between 0.2 and 0.3.