Preparation And Characterization Of CuInSe₂ Thin Films By One-step Electrodeposition

Energy-Economy-Environment problem is the major problems facing humanity in the twenty-first century, of which the energy problem is especially serious. Solar energy has many advantages, thus is an effective way to solve "3E" issue. Solar cell converts solar energy into electricity by using the photovoltaic effect, which is an important way for solar applications. CuInSe₂ (CIS) is a kind of direct band gap material, which is optical absorption coefficient up to 6×105cm^-1, low manufacturing cost, high conversion efficiency, and with stable performance, considered to be the most promising future optoelectronic material. The preparation methods of CuInSe₂ are vacuum evaporation, magnetron sputtering, molecular beam epitaxy, electrodeposition, screen printing, etc., of which preparing CI(G)S films by electrodeposition has the advantages of low-cost, high efficiency, Non-vacuum, safe environment, conducive to large-scale production and is widespread concerned.In this paper, with the aqueous solution of CuCl₂, InCl₃, SeO₂, KCl (electrolyte), sodium citrate (complexing agent) for the deposition, the CuInSe₂ thin films have been obtained by potentiostatic electrodeposition with a three-electrode cell. Then thin films have been characterized by scanning electron microscopy (SEM), scanning electron microscope energy dispersive spectrometer built (EDS) and X-ray diffraction (XRD). The main contents are following:First, the Mo thin films have been prepared by magnetron sputtering, and the relationships between the sputtering power and the deposition rate and surface morphology of Mo have been studied. The results show that: the relationship between sputtering power and deposition rate of Mo is linear. The Mo film surface roughness varied with the increase of sputtering power. When the sputtering power is 30W, the film grain is uniform and compact.Second, the electrochemical behaviors of Cu, In and Se have been investigated in individual electrodeposition and co-electrodeposition under different complexing agent concentration by cyclic voltammetry. Meanwhile, the influence of complexing agent concentration on the film morphology, phase structure and chemical composition have been also studied during preparing by potentiostatic electrodeposition, and better complexing agent concentration has been obtained by experiment.Third, the influence of deposition potential on the film morphology, phase structure and chemical composition have been also studied during preparing by potentiostatic electrodeposition, and better deposition potential has been obtained by experiment.Fourth, the CIS thin films have been prepared in an ideal complexing agent concentration and deposition potential, then selenium annealing. The influence of annealing time on the film morphology and phase structure have been also studied when the annealing temperature is 500℃, the appropriate annealing time has been obtained by experiment.The results show that sodium citrate presents the complexing effect on Cu²⁺ and HSeO_<sup>2+ but no effect on In³⁺. The chalcopyrite phase CIS thin films with surface dense, uniform particles, approximate to the ideal stoichiometric ratio have been obtained in the solution of 8mmol/L CuCl₂, 50mmol/L InCl3, 12mmol/L SeO₂, 200mmol/L KCl when the concentration of sodium citrate is 500mmol/L, deposition potential is -0.7V (vs.Ag/AgCl), annealing temperature is 500℃and annealing time is 60 minutes.