Atomic Layer Deposited Metal-Insulator-Semiconductor Junctions for Solar Fuel Synthesis

Energy storage to overcome the intermittency of solar radiation is a major challenge for adoption of solar energy at very large scale. Photoelectrochemical synthesis of fuels from sunlight is one potential storage approach.

Using sunlight to drive photoelectrochemical reactions requires electronically coupling light absorbing materials and catalysts to simultaneously achieve a) efficient absorption of sunlight, b) efficient electron-hole separation and transport, and c) surfaces with high electrochemical reactivity, all while avoiding corrosion or oxidation that would destroy one or more of the above properties. We have recently shown that atomic layer deposition (ALD) can be used to protect the surface of silicon so that it can serve as a stable photoanode for water splitting. Water oxidation, which has long been recognized as a key step in fuel synthesis from sunlight, is a photoelectrochemical reaction that would normally cause Si and many other high-quality absorbers to oxidize destructively.

This presentation will focus on our recent work in which ultrathin ALD-grown TiO2 provides a protective metal oxide passivation that stabilizes the heretofore unstable silicon surface under water oxidation conditions while also permitting facile hole transport to an overlying water oxidation catalyst. Mechanisms of electronic conduction in these nanoscale MIS junctions will be summarized, and the potential for extending ALD surface protection to other interesting absorbers beyond silicon will be discussed.

Speaker/Performer: Prof. Paul C. McIntyre, Stanford University, Materials Science & Engineering