Applications of Atomic Layer Deposition in Solar Fuel Synthesis

Abstract : Atomic layer deposition (ALD), a cyclic form of chemical vapor deposition which occurs via a series of self-limiting chemisorption reactions, is increasingly used in fabricating microelectronic devices because of its remarkable potential for depositing a very wide range of thin films of well-controlled thickness and uniformity over a large variety of substrates.  Exciting applications of ALD in energy technologies have also emerged in recent years, particularly in photovoltaics and micro-fabricated solid oxide fuel cells.  In this presentation, I will summarize recent research in which ALD has been used to prepare stable photoelectrodes for efficient solar-driven water splitting to create hydrogen fuel.  ALD-grown TiO₂ layers are found to be particularly effective in inhibiting oxidative corrosion of high-quality semiconductor absorbers and in electronically coupling these semiconductors to efficient catalysts for oxygen evolution, the kinetically-limiting step in water splitting.  This talk will describe factors influencing the electronic conductivity of ALD-TiO₂, and design principles for optimizing the photovoltage of these protected semiconductor junctions.   Atomic layer deposition of TiO₂-transition metal oxide alloy layers that can function as efficient oxygen evolution catalyst layers and high work function Schottky contacts for water splitting photoanodes will also be reported.