Preparation And Mechanism Of CZTS By Electrodeposition Assisted Sol-gel Method

Cu₂(Zn,Sn)S₄(CZTS)thin film,with the advantages of rich and non-toxic raw materials,low cost,ideal wide optical band gap of 1.4-1.5eV,and high absorption coefficient(?10⁴cm^-1),has been regarded as a green material to fabricate solar cells.The non-vacuum process of sol-gel has the advantages of controllable chemical compositions and low cost,becomes a common method to prepare CZTS film.The preparation of precursor solution by sol-gel method usually takes about4-12h and the reaction time is long,which is due to the slow REDOX reaction between bivalent Cu²⁺and bivalent Sn²⁺.In this paper,CZTS thin films were prepared by sol-gel method assisted by electrodeposition method.Firstly,Cu layer was deposited on Mosubstrate by electrodeposition method,which only took a few seconds to complete.(Zn,Sn)S₂ precursor solution was prepared by sol-gel method,and the preparation time was about 30min,which greatly shortened the preparation time of precursor solution;High quality CZTS films were prepared by spin-coating and annealing.In this paper,the CZTS thin film absorption layer with Cu/(Zn+Sn)=0.84stoichiometric ratio was prepared by sol-gel method assisted by electrodeposition.The phase and morphology of the CZTS absorption layer were analyzed by XRD,Raman and SEM.The formation mechanism of CZTS phase by electrodeposition assisted sol-gel method was studied.It was found that the intermediates formed during the growth of CZTS film prepared by electrodeposition assisted sol-gel method were Cu₃SnS₄ phase,which was different from the Cu₂SnS₃ phase in sol-gel method.The CZTS films prepared by the two processes were compared with SEM images.It was found that the new method inhibited the reaction between Mosubstrate and S element,and reduced the thickness of MoS₂ layer.The cell device with the highest photoelectric conversion efficiency of 4.45%was fabricated by the new method.In this paper,the effects of doped elements Ga and Sb on the properties of CZTS films and devices were studied by sol-gel process assisted by electrodeposition.It is found that Ga doping can effectively improve the open circuit voltageVOC of the device,and the photoelectric conversion efficiency of CZTS thin film solar cells is4.41%.The photoelectric conversion efficiency of CZTS thin film solar cells prepared with Sb doping is 3.71%.The effect of Na+K co-doping on the structure and morphology of CZTS films was further studied.Proper Na+K doping ratio is beneficial to improve the quality of CZTS films.Na+K co-doping inactivated the grain boundary,improved the surface morphology of CZTS film,and effectively inhibited the formation of secondary phase in the film.By analyzing the performance of solar cells,it is found that Na+K co-doping improves the open circuit voltageVOC,the shunt resistance Rsh and the filling factor FF.The photoelectricity conversion efficiency of CZTS thin film solar cells is 4.46%under the condition of 5%Na+K doping concentration.