Growth and characterization of electrodeposited Cu(In,Al)Se_2 thin films

摘要

Thin films of Culn(1-x)Al_xSe_2 were grown using a cathodic electrodeposition technique. The Culn(1-x)Al_xSe_2 films were electrodeposited on SnO_2 coated glass from aqueous baths containing different Al contents using deposition potentials ranging from - 650 mV to - 850 mV versus a saturated calomel electrode. The electrodeposited films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays, atomic force microscopy, and UV-VIS-NIR spectroscopy. The results show that single phase Culn(1-x)Al_xSe_2 films with Al content x around 0.27-0.33 having good stoichiometry can be produced in the above potential range. XRD and SEM studies show that films deposited at -650 mV and - 750 mV have good crystallinity while those grown at - 850 mV have comparatively poorer crystallinity. SEM studies show that the particle size of the films grown at - 650 and - 750 mV is in the micron range but is around 100 nm when grown at - 850 mV. Optical studies show that the optical band gap shifts with Al content from 1.21 eV for x = 0.27 to about 1.42 eV for x = 0.33. The as-grown as well as vacuum annealed films were n-type in conductivity with resistivity in the range 3-5 x 10~-3 Ωcm.