Efficient Encapsulation Strategies Of TOPCon,HJT And Perovskite Solar Cells

Solar cells are susceptible to environmental factors（e.g.temperature,humidity,UV light,etc.）.Proper encapsulation can improve the stability and lifetime of solar cells and prevent them from short-circuiting and leakage during use.Commonly used encapsulation materials include polymers,glass and metals.Among them,polymer materials have the advantages of low cost,light weight and easy processing,and are gaining more and more attention in the encapsulation of solar cells.In this thesis,three encapsulation films,corrosion-resistant EVA（ethylene vinyl acetate copolymer）,UV DC-EPE（UV-converted EVA-POE-EVA co-extrusion）and POE-g-KH570（modified polyolefin）,were successfully prepared by polymer resin modification methods to solve the TOPCon（tunneling through oxide layer passivation contact）,HJT（silicon-based heterojunction）and calcium titanite The encapsulation of solar cells was tested for ageing reliability in accordance with IEC standards.At the same time,the performance of the adhesive film is characterised and the modification options optimised by various means,and finally the application results are discussed in detail.These modified encapsulation strategies will provide more reliable and economical research ideas and solutions for the commercialisation of TOPCon,HJT and perovskite solar cells.The main research and conclusions of this thesis are as follows:（1）In the practical application of photovoltaic single-glass modules,the high water permeability of the backsheet leading to the vulnerability of the cell backside to acid corrosion has been a problem to be solved.In this chapter,EVA material is used as a modified matrix and Mg O（magnesium oxide）particle filler is added to EVA resin by melt blending to prepare corrosion-resistant EVA adhesive film.On the one hand,Mg O particles can neutralize the acid in the resin matrix to avoid acid corrosion of the cell sheet and metal grid line.On the other hand,the addition of appropriate amounts of inorganic nanoparticles can also improve the peel strength,heat resistance and bulk resistivity of the adhesive film.In addition,this study discusses the effect of different lamination temperatures and times on the performance of corrosion resistant EVA films and determines the optimum lamination process.The experimental results show that the corrosion resistant EVA with a small particle size and 1%Mg O content has the best performance after lamination at 145°C for 15 min.The power degradation after 1000 h of DH（damp heat）,10 cycles of HF（wet freeze）and 96h of PID（Potential Induced Degradation）was less than 5%when applied to the TOPCon battery package.This study provides a new solution for the packaging of lightweight and easy-to-install PV single-glass modules,which has unique advantages and prospects for PV building integration.（2）How to maintain or even improve the performance of solar cells under the influence of high temperature,high humidity and intense ultraviolet light has always been a challenging research topic.Here,this chapter propose a novel and effective solution by combining the benefits of EVA,POE（polyolefin）and UV down-conversion（UV-DC）fluorescent nanomaterial(Sr_2-xMg Si₂O_7-x:Eu²⁺,Dy³⁺)to construct the first commercially available UV-DC EPE co-extruded encapsu-lating film with a three-layer composite structure.On the one hand,the UV-DC EPE incorporates the high adhesive strength of EVA and the strong weather resistance of POE.On the other hand,the UV-DC EPE can also convert the UV irradiation,inefficient for power generation and easily cause damage to solar cells,into visible light range with high quantum efficiencies.Therefore,this study discovers that the UV-DC EPE not only shows higher stability than other encapsulation films under poten-tial-induced degradation,pressure cooker test（PCT）,UV and natural sunlight aging tests,but also enhances the power generation efficiencies by 0.3%and 2.3%compared with the UV-transmitting and the UV-filtering EPE films,respectively.The progress in this work breaks the stereotypical definition of encapsulation that only slows down attenuation,but inte-grates the advantages of power gain effect,high stability,and low cost into the novel encapsulation material and technology,which is expected to be promoted and industrialized in the near future.（3）Achieving high bonding performance of encapsulation materials under non-cross-linked lamination process conditions at low temperatures（below 100°C）is beyond the reach of current commercial PV encapsulation materials.In this chapter,a new solution is proposed to prepare POE-g-KH570 adhesive film by grafting KH 570（silane coupling agent）with POE.Compared to POE in a cross-linked system（above 140°C）,POE-g-KH570 can achieve an initial peel strength of 150 N/cm or more with glass under lamination conditions at 100°C.At 1%of BPO（initiator）and 1%of KH570,POE-g-KH570 has the best heat resistance with a high peel strength.In addition,two different encapsulation methods have been used to test the encapsulation of chalcogenide solar cells,and it was found that the overlay encapsulation has better encapsulation results than the wraparound encapsulation.This solution avoids the heat loss caused by organic photovoltaic materials during the high temperature encapsulation process and provides a new idea for the encapsulation of organic thin film cells and organic semiconductor devices.