| Nowadays, there is a growing interest shifts towards thin-film solar cells which is a promising alternative to silicon solar cells. Among them, chalcopyrite thin film solar cell has become one of the leaders in this field. Many research groups have reported the fabrication of high-efficiency copper-indium-gallium-diselenide(CIGS) solar cells by vacuum deposition processes, and a conversion efficiency of 20.8% has recently been achieved. Compared with the CIGS, the sulfide analogue of copper-indium-sulphide(CuInS2) is less toxic. Though its record energy conversion efficiency(12.5%) is much lower than that of CIGS, direct band gap of 1.55 e V, high absorption coefficient(~105 cm-1) and non-toxicity of the constituents are the important attributes of CuInS2(CIS) films to be used as an absorber layer in thin film solar cells. The theoretical value for CIS was calculated ranging from 27%-32%. Now, the relative lower conversion efficiency currently was mainly influenced by the qualities of CIS thin films. Hence, our researches have devoted to find the correlation between its preparation methods and the resulting properties in structure, morphology and device performances. There main research works are performed, which listed as follows: 1. The study on the Cu thin films deposited by a pulse electrodeposition technique with the galvanostatic mode.The uniform, densify and smooth of the Cu thin films were prepared by pulse-plating electrodeposition technique on FTO glass substrates in the galvanostatic mode from aqueous solution. And then, the influence of deposition parameters for Cu films morphology such as current, frequency, duty cycle and the concentration of complexing agent were explored. The results showed that the deposition current and duty cycle could regulate well the morphology of films. However, the but the quality of Cu film will become worse when the pulse frequency is inapproriate. 2. The fabrication of Cu/In bilayer and Cu-In allay thin films.First, the uniform and denser of the Cu layer was obtained from pulse-plating electrodeposition technique with galvanostatic mode. Then, In layer was deposited on the Cu-covered FTO to form Cu/In bilayer using the pulsed constant current mode. Finally, the Cu/In bilayer films were pre-heat treatment to form an intermetallic compound under vacuum condition in a double-temperature-zone tube furnace. The influence of current for the morphology of In films, deposition time of the In layers for component of Cu-In alloy thin films, the temperature of pre-heat treatment and persistent period for the morphology and structure of Cu-In alloy thin films were explored. The results showed that the quality of In layers became better with the increase of current. However, inappropriate deposition currents will resulte serious hydrogen evolution reaction during the electrodepositon. The Cu/In alloy film formed completely by heat treatment at the 120? for 30 min and 250? for 10 min. 3. The study on the CIS thin films by sulfurizing Cu-In allay films at high temperatureFirst, the uniform and denser Cu/In bilayers were obtained from pulse-plating electrodeposition technique over FTO glass substrates with galvanostatic mode. And then it was pre-heat treated to form an intermetallic compound. Finally, Cu-In allay films were sulfurized in a double-temperature-zone tube furnace together with sufficient sulfur powder at different sulfurization temperatures. The influences of sulfurization temperature and sulfurization period on the morphologies, structural, component and optoelectronic properties of the CIS films were explored. The results showed that the CIS film obtained at 600? for 30 min have better optical and electrical properties, which was more promising for photovoltaic applications than those prepared at low temperatures and short sulfurization time. A preferable ration of Cu/In/S closer to 1:1:2 was approached as proved by the EDS. Raman analysis indicated that the binary CuS phases were not presented in the CIS film. |
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