Preparation,Performance And Application Research Of Transparent Thermoplastic Polyurethane Film For Solar Cell Packaging

At present,China's solar cell packaging materials market is dominated by ethylene-vinyl acetate copolymer(EVA)film.In the curing process,it occurs cross-linking reaction,and forms a three-dimensional network structure.EVA films play an important role in the solar cell packaging.But there are several obvious drawbacks such as poor weatherability,bad stain and mildew resistance,low production efficiency of the solar cell module and so on.Therefore,in practical applications,if a super-weather-resistant thermoplastic polymer material can replace the EVA film as solar cell packaging material,it will show a huge application value for no cross-linking in packaging process.Transparent thermoplastic polyurethane(TPU)has the advantages of good transparency,mechanical properties and adhesion,which is widely applied in industry.TPU film meets the need of the light transmittance and adhesive capability of packaging materials basically.It is expected to be used as a new solar cell packaging materials.In this paper,based on the design and application of transparent TPU films for solar cell packaging,a series of transparent TPU films were prepared by orthogonal design method to optimize the TPU synthesis conditions.Then,fluorine-containing chain extender(BPAF)was introduced to modify TPU,and the FTPU film with high transparency,yellowing and good weather resistance was obtained.Finally,the FTPU film was used as solar cell packaging material in order to explore the performance of PV modules.Specific conclusions are as follows:(1)TPU films were prepared by a two-step solution addition polymerization with isophorone dicyanate and PTMG as the main raw materials and 1,4-butanediol as chain extender.An orthogonal designing L16(45)was adopted to optimize the polymerization recipe and parameter.The transparent TPU film was characterized by FTIR,DSC,WAXD,UV-Vis,color difference and yellowing index.(2)To improve heat resistance and weatherability of TPU film,the fluorine chain extenders(BPAF)was introduced.A series of FTPU films were synthesized by using PTMG and PCL as soft segments respectively.The relationship between hydrogen bond,phase separation and transparency was studied by FTIR,WAXD,AFM and UV-Vis.The thermal resistance of FTPU film was characterized by TG.Finally,the light transmittance,color difference and yellowing index of FTPU and TPU film were analyzed after thermal aging and UV aging test.When the content of fluorine is 6.1%(FTPU-3),the light transmittance can reach 91.5%,and perform great heat and weather resistance.(3)The encapsulation process of FTPU-3 film was determined by using EVA film as the reference.The mechanical properties,volume resistivity,shrinkage rate and peel strength of the FTPU-3 film were characterized by EVA film as the standard of the encapsulation material.Finally,EVA and FTPU-3 films were used as encapsulated materials for monolithic silicon cell packaging.Comparison of photoelectric conversion efficiency and package power loss results show that the encapsulation effect of FTPU-3 film as solar cell packaging material is equivalent to that of EVA.