| Due to the Fresnel reflection on the material surface, most of the incident lighthave been reflected, which decrease the the sensitivity and efficiency of theoptoelectronic devices. Surface anti-reflective structure can suppress the lightreflection and improve the light absorption. Therefore, more and more attentionshave been paid to fabricate anti-reflective structures and many methods have beenapplied. Such as electron beam lithography, nanoimprint and laser interferenceetching. Among them electron beam lithography has the advantage of goodprecision, high-resolution and so on. However, it is expensive, low efficiency, anddifficult to achieve a large area, so it is not suitable for industrial production.Nano-imprint and laser interference etching can achieve large area anti-reflectivestructure. However, these technologies need expensive instruments as well asnano-imprint templates. So their applications have been limited. In addition,nanosphere lithography, combined with reactive ion beam etching, has also beenextensively studied. But its processing procedures are complicated and difficult to achieve large area which limit its application. On the other side, these methodsonly can achieve the construction of the two-dimensional antireflective structure,But it is difficult to fabricate three-dimensional antireflective structure.Particularly, three-dimensional anti-reflective structure has superior anti-reflectiveperformance and better superhydrophobic self-cleaning ability. Herein, wedeveloped a fast, low-cost and large area approach to build three-dimensionalantireflective micro-nano structure. In the approach, anisotropic etching of siliconin alkaline solution, metal catalytic etching and the hydrothermal synthesismethod are used to prepare three dimensional antireflective micro-nano structure.The corresponding sections of the studies are described as follows:(1) We developed a simple, inexpensive method for preparing antireflectivestructure over large area, the structure gave a good antireflective properties. Itsreflection could be reduced to5%. In addition, after modified by thefluorine-based silane reagent, the structure had excellent superhydrophobicproperties. Moreover, the antireflective structure could be transferred to thepolymer surface, the transfered polymer structure also had an excellentsuperhydrophobic properties. Therefore, this method also provides a new way forthe preparation of flexible superhydrophobic materials.(2) Anti-reflective surface can increase the absorption of sunlight. Meanwhile, theheterojunction structure will promote light-induced charge separation and reducethe combination of them. Both the study about them have made great progress. Ifthe advantage of each structure could be realized in one device, it may get ahigher solar energy utilization. In this thesis, we try to built a micro-nano composite antireflective structure with p-n junctions, the study found that suchstructure not only improved the antireflective properties of the material, but alsoenhanced the photo-electron conversion efficiency. Furthermore, its properties inthe degradation of dye molecules have been investigated.(3) We have prepared three dimensional ZnO/Si micro-nano compositeanti-reflective structure, the structure has superior antireflective properties andphotocatalytic properties. However, the ZnO nanorods are not so stable and lightlycorrosion will be happened in the photocatalytic process. So the performance ofdegradation and the protection for silicon also will decreased. TiO2has similarOptical and electrical properties to ZnO, but better chemical stability, therefore,TiO2/Si micro-nano composite antireflective structure should have a betterperformance. In the thesis, we build a three dimensional TiO2/Si antireflectivemicro-nano structure. Moreover, to further improve the photocatalytic activity ofthe material, Au nanoparticles were deposited on the surface of TiO2structure. Itsapplication in the degradation of the dye molecules has been explored.
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