Growth and characterization of electrodeposited Cu(In,Al)Se2 thin films

Thin films of CuIn_1 − xAl_xSe₂ were grown using a cathodic electrodeposition technique. The CuIn_1 − xAl_xSe₂ films were electrodeposited on SnO₂ 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 CuIn_1 − xAl_xSe₂ 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 × 10⁻³ Ω cm.