Fabrication And Application Of Biomimetic Lotus Leaf Structure Film

Environmental factors have become particularly severe in recent years,with irreversible effects on a global scale.In order to realize the long-term sustainable development of human society,clean and renewable energy represented by solar energy has received extensive attention.However,the current photovoltaic devices are generally faced with problems such as low utilization of solar energy and easy surface pollution.Therefore,it is critical to study optical thin films with antireflection and self-cleaning properties to improve the performance of photovoltaic devices.Inspired by the self-cleaning phenomenon of natural lotus leaves,this subject systematically studies the microstructure and optical mechanism of the surface of natural lotus leaves.A biomimetic lotus leaf micropapillary film with anti-reflection and self-cleaning properties was prepared,so as to achieve the purpose of increasing the light conversion efficiency of monocrystalline silicon solar cells.Taking the natural lotus leaf as the prototype,the microscopic morphology of the leaf surface was firstly analyzed and characterized by scanning electron microscope(SEM).It was found that a large number of irregularly arranged micro papillae were distributed on the surface of lotus leaf.There are also nano-scale fluffy substances on the edge profile,which are called waxy nanowire structures.It has low surface energy and constitutes a micro-nano composite structure.Secondly,the reflectance spectrum of the natural lotus leaf surface was measured by an ultraviolet spectrophotometer with an integrating sphere,and it was found that the natural lotus leaf structure has good anti-reflection performance in the visible light range of 300 nm-700 nm.In order to more vividly illustrate the antireflection mechanism of the natural lotus leaf structure,the surface structure of the lotus leaf was modeled and simulated by FDTD optical simulation software.Then,the static contact angle of water droplets on the lotus leaf surface measured by a contact angle meter is about 152.1 ± 0.34°,which has superhydrophobic properties,which is mainly attributed to the special micro-nano composite structure on the lotus leaf surface and the wax with low surface energy.The result of the interaction of the nanowire structure.Based on this,we successfully prepared NOA81 based biomimetic lotus leaf microstructure films by PDMS template method and nanoimprinting method using natural lotus leaf as the main body.The research results show that the NOA81 based biomimetic lotus leaf microstructure film imprinted by the template method can only roughly replicate the micropapillary structure on the surface of the lotus leaf,but the nanowire structure on the surface cannot be replicated,indicating the limitation of the template method.The NOA81-based bionic lotus leaf microstructure film measured by UV spectrophotometer has an average reflectance of 24.5 ± 0.25%,which retains the anti-reflection properties of natural lotus leaves.The self-cleaning and solar cell testing experiments show that the NOA81-based bionic lotus leaf microstructure film not only improves the photovoltaic efficiency of monocrystalline silicon solar cells,the photoelectric conversion efficiency value reaches 16.07%,but also acts as a protective film for photovoltaic devices,which plays a role in Self-cleaning effect.In order to optimize the self-cleaning performance of the bionic lotus leaf film.Based on the preparation of NOA81-based biomimetic lotus leaf microstructure films,zinc oxide(ZnO)nanowire structures were grown on the surface of micropapillae combined with hydrothermal method.Thus,a micro-nano composite structure similar to the surface of the natural lotus leaf is formed.We also investigated the effects of hydrothermal growth solution concentration and hydrothermal growth time on the growth length of ZnO nanowires,respectively.The surface morphology of the composite film was obtained by SEM.The microstructure of the nanostructure was obtained by high-resolution transmission electron microscopy(HRTEM),and the elemental composition of the composite film surface was measured by the attached EDS detector.The crystal structure of the ZnO nanowires was characterized by X-ray diffractometer.The elemental composition of the surface of the composite structure film was analyzed and tested by X-ray photoelectron spectroscopy.The prepared composite film has obvious superhydrophobicity after silanization treatment.The water droplet contact angle(CA)of the composite film was measured by a contact angle meter,showing a superhydrophobic surface similar to a lotus leaf.Through the self-cleaning experimental test,the self-cleaning ability of natural lotus leaf is simulated.This research is based on natural plant prototypes.Through the biomimetic natural lotus leaf surface structure,optical films with anti-reflection function and superhydrophobic self-cleaning properties for solar cells were prepared.The simplification of the preparation process is realized,and the material selection is convenient.It provides a certain reference value for the manufacturing of commercial and functional optical thin films.