Fabrication of 3D biomimetic composite coating with broadband antireflection, superhydrophilicity, and double p-n heterojunctions

摘要

The traditional single material with two-dimensional (2D) biomimetic moth-eye structures is limited by its narrowband antireflection and single functional capability.To overcome these disadvantages,we exploited wet etching and hydrothermal synthesis coupled with chemical oxidation for fabricating a threedimensional (3D) biomimetic moth-eye coating with ternary materials (polypyrrole nanoparticles,TiO2 nanorods,and Si micropyramids,i.e.,PPy/TiO2/Si-p).This coating reduced the reflectivity to ＜4％ at wavelengths ranging from 200 to 2,300 nm and exhibited remarkable superhydrophilicity with a low water contact angle of 1.8°.Moreover,the composite coating had double p-n heterojunctions,allowing the high-efficiency separation of photogenerated carriers.The photocurrent density of PPy/TiO2/Si-p was more than three times higher than that of TiO2/Si-p at a positive potential of 1.5 V.The proposed method provides a means to enhance solar energy conversion.