Design Of Polymer Multilayer Optical Film And Its Application In Photovoltaic

In order to meet the challenges of climate change and achieve the strategic goal of carbon neutrality,it is imperative to develop renewable energy.In view of the wide spectrum of sunlight,rational use of solar energy in frequency bands that are not suitable for photovoltaic power generation can be converted into corresponding thermal energy,chemical energy and biological energy,which can greatly improve the efficiency of solar energy utilization.In order to realize the reasonable utilization of solar frequency division,firstly,a selective filter based on the principle of multilayer optical interference must be designed and prepared.The traditional multilayer interference filter is usually prepared by vacuum coating.The process is characterized by low coating efficiency and can not be produced on a large area,so the production cost is too high and cannot be applied to a solar photovoltaic frequency division utilization system on a large area.The development of an efficient and low-cost selective filter preparation technology has become a core key issue in whether the solar energy frequency division and efficient utilization technology can be widely promoted and applied.In order to solve this problem,this dissertation starts from the principle of wave optics,using two low-cost polymers with different refractive indexes as raw materials,through the process of stacking multiplication and co-extrusion to achieve the preparation of periodic structure alternately stacked polymer multilayer films(PMF).Combining and stacking periodic structure films of different thicknesses can prepare single-pass and multi-pass band filter with wavelength selectivity.The polymer multilayer co-extrusion technology can quickly obtain hundreds or thousands of multilayer periodic structures at one time,which provides the possibility to prepare a large-area,low-cost multilayer interference filter film.The research content of this article is as follows:(1)The principle of wave optics and the basic theory of multilayer optical film design was introduced.TFCalc optical simulation software was used to analyze the influence of film thickness,period logarithm,material refractive index difference,incident light angle,etc.on the center wavelength position,reflectivity and reflection bandwidth of the optical film.According to the technical characteristics of polymer multi-layer co-extrusion,by comparing and analyzing the rheological and optical properties of different polymer materials,Polycarbonate(PC)with high refractive index and Polymethyl methacrylate(PMMA)with low refractive index are determined as the material combination for the design and preparation of the polymer multilayer optical film in this paper.The flexible and stretchable blue shift characteristics of the polymer multilayer film and the broadening method of the reflection bandwidth are studied,and a novel design scheme of the polymer multi-passband optical film is innovatively proposed.(2)Experimental platform based on PC/PMMA polymer materials for multilayer co-extrusion cast film and film stretching technology was designed and actually built.The design adopts 3 single-screw extruders,3 times distributors,one to four type"equal division" stacking multiplier,one to two type "non-equal splitting" stacking multiplier as the main hardware structure,equipped with vacuum dryer,automatic loading system.The process technology has the preparation conditions for the number of layers up to 640 layers of PC/PMMA polymer multilayer film.(3)The design and preparation method of the PC/PMMA multilayer reflective film with ultraviolet resistance are studied.The PC/PMMA anti-ultraviolet film can selectively reflect the ultraviolet wavelengths in sunlight,and selectively transmit the other wavelengths that are beneficial to the power generation of crystalline silicon photovoltaic cells.Compared with conventional PV glass which has transmissivity greater than 90%at 400-1200 nm,the PMF we designed has equivalent transmissivity between 410-1200 nm and high reflectance(R>90%)at 320-400 nm.The glass-free and semi-flexible crystalline silicon PV module has a power generation efficiency of 20.37%and the efficiency of the control group with glass as a cover layer is 20.67%.The weight of our designed module can be greatly reduced by 85%.The anti-aging experiment shows that the PC/PMMA multilayer film has excellent anti-ultraviolet aging characteristics,which can meet the conditions of long-term outdoor use.The design method of PC/PMMA multilayer infrared reflective film is also studied.The use of polymer infrared reflective film has excellent thermal insulation properties,and using it as the backsheet material of crystalline silicon battery modules can effectively reduce the temperature of the photovoltaic module,thereby improving the power generation efficiency of the crystalline silicon photovoltaic module.(4)In view of the solar spectrum response of crystalline silicon photovoltaic cells and the demand of plant photosynthesis spectrum,the design and preparation method of PC/PMMA polymer three-pass band filter film are studied.The three-pass band filter film is used to selectively transmit blue light(450 nm),red light(660 nm),and far red light(730 nm)suitable for plant growth in sunlight,and the rest of the sunlight is reflected and concentrated to generate electricity,which realize the comprehensive utilization of solar photovoltaic power generation and plant photosynthesis frequency division.Through the design and construction of an agricultural photovoltaic system that does both planting and power generation,the power generation efficiency test,system cost analysis and crop planting test were carried out.The experimental results show that compared with open-air crop cultivation,after selective filtering,the yield of rapeseed and other crops is not only unaffected,but slightly increased.