Research Of Biomimetic Moth-eye Antireflection Glass And The Application In Photovoltaic

Solar energy is a renewable,clean energy source and is expected to solve the problem of energy depletion and environmental pollution.Photovoltaic modules are the devices that directly convert solar energy into electrical energy.In the photovoltaic modules,due to the difference of the refractive indexes between the air and the cell window glass,the incident light is greatly reflected at the interface and will be more pronounced in oblique incidence.Therefore,suppressing light reflection is the key to improve the battery performance.Researchers often use the principle of optical interference preparing a low-refractive-index antireflection layer in 1/4 wavelength,but this can only achieve low reflectivity in relatively narrow wavelength bands.Inspired by the moth-eye,researchers have developed micro-nanostructures on the substrates,that is,moth-eye structure,to obtain a graded refractive index from the air to the substrate,aiming at realizing broad spectrum,wide-angle antireflection.In previous works,researchers mostly used nano-imprinting or micro-casting methods to build moth-eye structures on polymer films.Although they have excellent anti-reflection effect,they have poor mechanical strength and are difficult to withstand the harsh outdoor conditions for conventional photovoltaic modules.In this paper,we use self-assembled metal Cu nanoparticles generated in dewetting process as the dry-etching masks to obtain three-dimensional(3D)moth-eye structures on the glass surface.The following brief results are obtained:(1)Annealing process shrank the Cu film dewetting into nanoparticles.The increase in hydrogen content favors the production of uniform size and regular Cu nanoparticles.The particle diameters increase with the thickness of the film,but the particle density and fraction show the opposite trend.The temperature range of 400-600°C and the time range of 10-60 min rarely affect the morphologies of the nanoparticles.(2)In the inductively coupled plasma etching(ICP)process,prolonging the etching time increases the height of the nano-cone and facilitates light transmission.However,longer etching time will also cause the loss of the nano-masks,which will eventually destroy the moth-eye structures.Thicker film lead to the larger diameter of the formed particles and further increase the top diameters diameter of the nanocones,which is detrimental to antireflection results.On the other hand,the thinner film has insufficient resistance to etching process.Therefore,the thickness of the thin film and the etching time must be weighed.The ICP etched single-side moth-eye glass has a transmittance of over 97%,while the double-sided etched samples have a transmittance of 99%and over 99.5%at 400-670 nm.Samples etched in reactive ion beam etching(RIE)process show relatively low antireflection effect comparing to the ICP etching ones,because of the optical platform on the top as well as the insufficient heights.(3)The prepared moth-eye glass can greatly reduce the light reflection on the surface of the photovoltaic modules in the 300-1100 nm band,and can obtain<3%reflectivity in the range of 570-950 nm.The photoelectric conversion efficiency(PCE)of the modules was increased by 4.6%at normal incidence and 9.9%at 60~o,showing excellent broadband and omnidirectional antireflection capabilities of moth-eye glass.(4)The water contact angle of the moth-eye glass is about 0~o,and it has superior super-hydrophilic self-cleaning and anti-fogging properties,which is very beneficial for improving the efficiency of light energy utilization.(5)Sand-ablation test and pencil hardness test confirmed the superior mechanical strength of the moth-eye structures,which contributes to the long-term use of photovoltaic modules in outdoor applications.In this paper,the biomimetic 3D moth-eye glass was simply and efficiently prepared through thermal annealing of metal thin films and the following ICP etching.The glass not only has excellent antireflection properties,but also has super-hydrophilic self-cleaning,anti-fogging properties and excellent mechanical robust properties.The moth-eye glass not only can be used to improve the efficiency of photovoltaic modules,but also can be used in automotive rearview mirrors,optical lenses,organic light-emitting diodes(OLED)and other fields.