Research On Surface Integrity Of CIGS Solar Thin Films In Shear Forming Process

With the rapid development of the photovoltaic industry,copper indium gallium selenide(Cu(In,Ga)Se2,CIGS)solar thin-film cells are considered to have the most development prospects due to their advantages such as flexibility,light weight,high conversion efficiency,and low cost.One of the thin-film solar cells,striving to improve its photoelectric conversion efficiency is the research goal of this article.At present,the CIGS solar thin film with stainless steel as the substrate is a battery cell composed of battery cells with a certain length and width after the film is deposited.Because the surface film has different mechanical and material properties,The film layer is prone to damage,chipping,and delamination with the substrate during shearing and forming,resulting in shear edge damage,which affects the photoelectric conversion efficiency of the battery.In this paper,the CIGS solar thin film is taken as the research object,and the influence of the shear forming on the shear edge damage is studied.First,the structure and performance of the thin film layer on the surface of the CIGS solar thin film were analyzed.The hardness of the thin film layer was measured using a nanoindenter,and the bonding force of the thin film layer and the stainless steel substrate was detected by the RST scratcher.The results show that the nanohardness(HIT)of the film layer is 0.95159 ± 0.4GPa,the elastic modulus(EIT)is 45.14 ± 1GPa,and the bonding force between the film and the substrate is 7.71 N.Secondly,the cutting edge damage rule of the CIGS solar film sheet during the shear molding process was studied.The shear edge of the commercial CIGS solar film unit sample was detected and found that the average width of the film peeling area was 88.392 um,and the maximum width of the average affected area is 96.624 um,and the average shear edge breakage rate is 3.262 ‰.This will have an impact on the CIGS solar thin-film photoelectric conversion efficiency.Further,using an energy spectrum analyzer(EDS)to detect the sheared samples,it was found that when the shearing process is stressed,the thin film layer is likely to be at the interface between the CIGS absorber layer and the Mo back electrode layer and the Mo back electrode layer and stainless steel Interface peeling occurs at the interface of the substrate layer,and interlayer peeling occurs in the CIGS absorber layer.By optimizing the cutting parameters,the cutting edge damage can be effectively reduced.Thirdly,the effects of shearing process parameters and cutter geometry parameters on the shear edge breakage rate of CIGS solar thin film were studied.With the increase of the shear gap,the damage range of the film on the surface of the cut edge increases,and the damage range of the film is the smallest when the shear gap is 0 ?m;at the same time,the shear forces Fz and Fy gradually increase first and then decrease as the shear gap increases.As the shear rate increases,the film damage range decreases first and then increases.When the shear rate is 100 r / min,the film damage range is the smallest.Three types of pressure plate restraint types(without pressure plate,flat plate pressure plate,and V-type pressure plate)are used to perform shear experiments on the CIGS solar film,and the V-type pressure plate has a good effect.Four kinds of cutters with cutting edge radii(10?m,15?m,20?m,25?m)and five different texture cutters(the angle between the texture groove direction of the cutter and the edge of the blade edge ? are 0 °?45 °? 90 °?Ordinary no texture?V-shaped texture)carried out shear processing experiments,and found that the smaller the cutting edge radius of the cutter,the better the cutting edge film performance is.The texture structure of the cutter surface has a significant impact on the processing effect.In addition,the cutter with a Vshaped surface texture has the smallest film damage at the cutting edge.Finally,through three-point bending and tensile experiments on CIGS solar film,it is found that the compressive strength of CIGS solar film is much greater than its tensile strength.When the film is subjected to compressive stress,The cracks in the thin film layer will extend along a certain angle with the stainless steel substrate,and at the same time,lateral cracks parallel to the stainless steel substrate will also be generated.When these cracks merge,the film peels off;when tensile stress is applied,the small longitudinal cracks inside the film gradually evolve Large cracks,extending along the direction of the vertical stainless steel substrate to the interface between the two,until the film is peeled off after contact with other transverse cracks,when the tensile strain reaches 2.1%,the surface film begins to show local peeling,when stretched When the strain reaches 5.1%,large-scale film peeling occurs.