Fabrication Of CuSbSe₂Thin Films And Solar Cell Device Via Electrodeposition

CuSbSe2-based IB-VA-VIA2chacolpyrite semiconductor compounds are very promising materials for photovoltaic applications due to the based on nontoxic and earth-abundant materials and their excellent optical-electrical properties. CuSbSe2is a kind of a novel absorber layer material for thin film solar cells which our country have remarkable resource advantage. It is expected to replace Cu(In1-xGax)Se2(CIGS) in thin film solar cells because of solving the problem of resource shortage which restricted the development of CIGS solar cells. Electrodeposition of CuSbSe2thin film is a low cost non-vaccum method, which has the expection for large-scale production. Normally, the as-deposited CuSbSe2based on electrodepositon need heat-treatment to improve its crystallity.Rapid thermal annealing (RTA) is a powerful annealing technique and a very popular thermal treatment method for semiconductor device fabrication because of several advantages such as short cycle time, high heating rate and short heat treatment time to conventional furnaces. It can effectively reduce the volatile components such like Sb and Se escaped from CuSbSe2thin film.The aim of this paper is to investigate the electrodeposition mechanism of CuSbSe2thin film, and to show how the compositon, morphology and structure of the eletrodepostied films can be modified by different heat-treatments using characterization techiques of CV\SEML EDS、XRD、UV and PEC analysis. We also farbricated the CuSbSe2thin-film solar cell devices and sought their modification research. The main research conclusions are as follows:(1) We use the cyclic voltammetry tests to investigate the electrodeposition mechanism of CuSbSe2thin film. The most suitable deposition potential for films preparation was determined to be about-0.40V vs. SCE with stoichiometry close to1:1:2ratio, compact and homogeneous surface morphology with isolated grains of uniform size combining with cyclic voltammetry, composition and morphology studies. Both Cu-rich and Cu-poor thin films exhibit polycrystalline nature with the main phase of CuSbSe2and secondary phase Sb2Se3after rapid thermal annealing. Cu-rich and Cu-poorfilms show a high optical absorption coefficient larger than7×104cm-1and the same optical band gap of about1.09eV. Based on the results of PEC characterizations, it can be concluded that Cu-poor thin film has the better photoelectrical properties than those of Cu-rich thin film.(2) The effects of the temperatrue, heating rate, the holding time of RTA technique on the properties of Cu(In,Ga)Se2thin films were comprehensively studied. The results show that RTA treatments can inhibite the escape of volatile elements such as Sb and Se and provide significant improvements in crystallinity. As the temperature increased, the crystallinity of the film gradually strengthened but the morphology turned bad. The most suitable heating temperature for RTA was demonstrated to be about420℃with stoichiometry close to1:1:2ratio, compact and homogeneous surface morphology with isolated grains of uniform size combining with composition, morphology and XRD studies. Both higher heating rate and longer holding time during the RTA treatment did not significantly enhance its crystalline.(3) The CuSbSe2thin film solar cell devices were fabricated and we had explored its modification. The conversion efficiency of the device is0.395%, the open-circuit voltage is264mV, the short-circuit current density is only5.11mA/cm2, and the fill factor is only0.293. Short-circuit current and the efficiency of the device are low, and there is still have much room for improvement. Then we studied on the modification of CuSbSe2by sulfide and selenide, and CuSb(Sex,S1-x)2thin film which annealed in sulfur atomosphere had good photovoltaic performance. The device efficiency of CuSb(Sex,S1-x)2was0.204%; the as-deposited CuSbSe2after selenide heat treatment became Cu3SbSe4thin film, but film surface was porous and the device was shorted out.