Hierarchically structured electrodes prepared from selective atomic layer deposition in self-assembled, composite colloidal films.
by Norman, Mya A.; Perez, Walker; Coridan, Robert
Hierarchically structured materials are employed for applications that depend on the coordination of chem. and phys. processes that function on disparate length scales. An example is photoelectrochem. energy conversion, where the electrode structure must optimize the balance of light absorption, carrier collection at a semiconductor-liq. junction, electron transfer, and mass transport of reactants in order to maximize the energy conversion efficiency of the system. Strategies for designing electrodes generally depend on techniques borrowed from semiconductor fabrication, which allow precise control for prototyping, but are not readily transferrable to the development of scalable materials. Here we describe the fabrication of hierarchically structured electrodes based on selective at. layer deposition of ZnO in composite colloidal films. The distinct chem. susceptibilities of SiO2 and polystyrene nanospheres can be used to generate hierarchically porous materials. By choice of the initial colloidal components, the characteristic length scales for light absorption, carrier collection, and mass transport can be independently engineered into a thin film electrode for photoelectrochem. applications. Optimized nanostructured conductive scaffolds can be prepd. with a facile, continuously tunable, soln.-phase synthesis. This approach offers a scalable route for synthesizing nanostructured photoelectrodes based on strategies developed from more complex fabrication techniques.