Thiol-Based Solution Processed Cu₂ZnSn?S,Se?₄ Thin Film And Its Properties

Cu2ZnSn(S,Se)4 semiconductor materials become potential solar-cell materials because of their adjustable band gap(1.0?1.5 eV)and high light absorption coefficient(>104 cm-1).The theoretical efficiency was reported as high as 32.2%,however the highest photoelectric conversion efficiency of current devices is 12.4%.This paper describes an optimized method for air deposition based on the mercaptan solution system.In this improved method,metal salts and thiourea are used as initial materials to dissolve in a mixture of thioglycolic acid and thioglycolic acid,resulting in a homogeneous precursor solution.Prefabricated films of Cu,Zn,Sn and Se can be obtained by spinning the precursor solution in air and forming large grain Cu,Zn,Sn and Se films after selenization.A summary of the work is as follow1.A simple and low toxicity molecular premise solution method was developed to prepare Cu2ZnSn(S,Se)4 thin film solar cell.CZTS precursor solution was obtained by dissolving copper acetate,zinc chloride,stannous chloride and other salts in a system of ethylene glycol methyl ether-mercaptoacetic acid.Then the precursor solution was rotated-coated and annealed to obtain CZTS precast film.CZTSSe film was obtained by optimizing the selenization process,and its structure,morphology,composition and elemental valence state were analyzed.It was found that the film formed into pure phase,less copper and rich zinc(Cu/(Zn+Sn)=0.91,Zn/Sn=1.20)when the selenization temperature was 540?,with a high degree of crystallization,large grain size and good electrical performance.In addition,it is found that the system can also dissolve other metal salts,such as:Co(CH3COO)2·4H2O,Ni(CH3COO)2·4H2O,Cu(CH3COO)2·H2O,Mg(OH)2,Ca(OH)2,Mn(CH3COO)2,ZnCl2,SnCl2·2H2O,SbCl4,La(NO3)3·6H2O,and Ce(NO3)3·6H2O etc.2.Cu2ZnSn(S,Se)4 films with different Mn components(doping ratio 0%;1%;3%;5%;7%)were prepared by mercaptan solution method and the above process conditions.The crystal structure,morphology and valence state of elements were studied systematically.It was found that Mn element successfully enters CZTSSe lattice.With the increase of Mn content,the grain size increases and shows a uniform surface distribution.The crystallinity of the film was the best for the content of Mn was 3%.The effect of Mn on the properties of thin films was investigated in detail by using XRD,SEM,EDS,XPS,AFM,Raman and Hall3.The study investigated the incorporation of Mg ions into the precursor solution.The precursor solution mixed with different trace components(doping ratio:0%;1%;3%;5%;7%)of Mg element can improve the crystallinity,density,and quality of absorbing layer.More details of the effects of Mg doping on the properties of thin films were investigated by XRD,SEM,EDS,XPS,Raman and Hall characterizing and testing...