A new ZnO nanotetrapods/SnO2 nanoparticles composite photoanode for high efficiency flexible dye-sensitized solar cells

We report a new photoanode for flexible dye sensitized solar cells based on a judicious combination of SnO2 nanoparticles and ZnO nanotetrapods and the development of an effective low temperature fabrication technique of "acetic acid gelation-mechanical press-ammonia activation''. A 4.91% efficiency has been achieved on an ITO-coated polyethylenenaphthalate (ITO/PEN) substrate under 1 sun equivalent illumination. The peculiar symmetrical branching morphology of ZnO nanotetrapods is beneficial to charge collection of the SnO2/ZnO composite photoanode. The formation of a thin ZnO shell on SnO2 nanoparticles, after ammonia activation, is critical to boosting the open-circuit photovoltage and to improving inter-particle contacts as well as photoelectron injection. The mechanical press, apart from enhancing film durability, has also significantly improved charge collection.