Ordered multilayer films of hollow sphere aluminium-doped zinc oxide for photoelectrochemical solar energy conversion

Transparent conducting oxides (TCO's) are integral to many optoelectronic devices used for a range of display and solar energy technologies. Non-planar, 3-dimensional, TCO's offer the opportunity to support thin films of functional materials to increase light absorption, charge extraction, and wavelength-dependent manipulation of light if ordered into photonic structures. In addition increased surface area is also important for applications which rely on interfacial phenomena such as photoelectrochemical solar energy conversion, which is the focus of this investigation. Photoelectrodes have been fabricated from ordered spherical arrays of aluminium doped zinc oxide (AZO) and subsequently coated with photoactive semiconductor (CdS) nanoparticles using simple solution chemical deposition. The spheres of the structured AZO TCO are hollow and access to the internal volume supports loading of CdS as a thin film which results in increased light collection per geometric surface area. Efficient charge collection is observed, without restricting diffusion of electrolyte, allowing photocurrents ca. 20 times greater than a planar analogue.