Preparation and Characterization of Co-Se Thin Films by Electrodeposition

Cobalt selenide thin films were prepared onto tin oxide-coated glass substrates by electrodeposition method. The electrochemical mechanisms for this thin film formation were investigated by cyclic voltammetry (CV), and the results show that cobalt selenide compound phases are formed via either surface induced reduction by predeposited selenium or directly reaction with H2Se from six electron reduction of H2SeO3. It is also found that films' stoichiometry and morphology are significantly influenced by deposition potential, deposition temperature and pH value. Se-rich CoSe thin films with hexagonal crystal structure and compact morphology can be obtained at deposition potential of -0.5V (vs SCE), deposition temperature of 50 degrees C and pH value of 2.0. The electrodeposited CoSe film shows an optical absorption coefficient of higher than 1 x 10(5) cm(-1), and an optical band gap of (1.53 +/- 0.01) eV which is close to the theoretical optimization value of the light absorption layer materials in single-junction solar cell.