Controllable preparation of 2D and 3D ZnO micro-nanostructures and their photoelectric conversion efficiency

The different morphological ZnO micro-nanostructures were prepared by solvothermal method and their photoelectric conversion efficiency applied in dye-sensitised solar cells (DSSCs) were be analysed. The morphologies and crystalline structures of the ZnO nanocrystals grown under different driving forces, which were characterised by scanning electron microscopy, transmission electron microscopy and X-ray diffraction measurements. The results showed that different additives caused different growing directions for the crystal plane and then formed ZnO micro-nanostructures with different morphologies. The UV–visible diffuse reflectance spectra displayed that nanorod-assembled 3D urchin-like ZnO had the strongest absorbance intensity. When they were used as photo-anodes for DSSCs, the I–V curve showed their photoelectric conversion efficiency enhanced to different degrees. The highest was that of the nanorod-assembled 3D urchin-like ZnO micro-superstructures, which was synthesised under NaBH₄ and 25 % concentrated aqueous ammonia reaction system. Its photoelectric conversion efficiency is 2.37 %. Other hand, this simple and controlled method is promising to prepare the low-cost, environmentally friendly and high performance innovative structural materials.