Research On Preparation And Doping Modification Of CZTS Films

CZTS film materials have a lot of practical advantages which meet the current needs,thus standing out in a large number of solar cell materials.CZTS film material is a direct band gap P-type semiconductor with 1.5e V Band gap which result in a high optical absorption coefficient.The composition of the film's elements of the price is very cheap,and do no harm to the environment.Theoretically CZTS solar cell battery's efficiency can reach 32%.Definitely,CZTS film material has great potential in the photovoltaic device.In the preparation of CZTS films,sol-gel method is simple and convenient,which cost little.And the performance of the CZTS device is stable,therefore become the subject of the research.The traditional sol-gel method for preparing CZTS films is prone to problems such as poor film quality and poor battery efficiency.Based on this,the preparing process and the process parameters of CZTS thin films are optimized.By studying the changes of the surface morphology and phase structure of the films under different concentration of elements,The best element ratio of CZTS film is Cu/(Zn+Sn)=1,Zn/Sn=1.2,S/(Cu+Zn+Sn)=2.At this point,CZTS film composition is uniform and dense,the particles of the grain is large,And the phase is single Kesterite structure.On the basis of preparing high quality CZTS film,doping the film with different elements(Fe,Co,Ni,Mn).Research the effect of doping elements and their contents on morphology,phase structure and photoelectric properties of CZTS thin films.SEM analysis shows that a small amount of Fe and Ni doping can increase the grain size and improve the film flatness.Suppression the precipitation of Zn S phase.Doping Co can improve the film's grain size,but will lead to larger holes in the film.doping Mn can improve the density of the film,but has little effect on the grain size.XRD and Raman analysis show that doping with Fe did not lead to heterophase,and the preferential growth of(112)plane remains well.When the doping amounts of Co and Ni increase,heterophases occur and the prefering orientation of the(112)crystal plane decreases.heterophase occurs when doping a small amount of Mn,but the prefering orientation of(112)crystal plane is better.All of this shows that doping with Fe can improve the crystallinity of CZTS films.The doping of Co,Ni and Mn will reduce the crystallinity of films.With the increase of doping amount,due to the difference of the metal ion radius,the doping elements will distort the lattice when substituting Zn at the lattice position or into the lattice space,this phenomenon can be proved by different XRD diffraction peaks andRaman peaks Offset.By measuring the transmittance of the film and calculating the band gap width of the CZTS films,all the doping elements were found to reduce the optical band gap of the films.The films' resistivity test found that a small amount of doping elements can reduce the resistivity of the films.The dark current and photoncurrent test of CZTS film showes that a small amount of Fe doping can greatly improve the conductivity of CZTS films.Through the analysis above,CZ0.8F0.2TS thin film solar cell with a Fe content of 0.2 was prepared.The IV characteristics of which was tested,and its photoelectric conversion efficiency ? is 2.4%.