High performance solar photoelectrodes based on thin-film reactions

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This project aims to develop new devices that use power from sunlight to perform chemical reactions necessary to convert water to hydrogen and oxygen. Traditional devices for this application, referred to as photoelectrodes, suffer from fundamental tradeoffs between efficiency and longevity in operation, because materials that absorb sunlight efficiently are generally degraded under the required operating conditions. Also, manufacturing costs combined with limited performance have, to date, rendered the production of hydrogen from solar power with such devices uneconomic. A highly scalable, low-cost materials processing approach based on crystalline silicon (the same material used in the very large majority of commercial solar cells) has shown promise to yield high-performance, low-cost photoelectrodes. This project will advance fundamental science and engineering of generating chemical fuels from solar power with such materials, seeking to reduce the cost of “green” hydrogen to make it competitive with fossil fuels. Concurrently, the research team will develop projects and materials that will enable elementary and secondary school students to learn about renewable energy and fundamental properties of light, topics of increasing importance for citizens in our modern society, using a low-cost visible-light optical spectrometer, made from inexpensive everyday items and attached to a smartphone camera.This project seeks to design and develop metal-insulator-semiconductor (MIS) photoanodes and photocathodes for solar-driven water splitting that offer high performance, outstanding stability, and highly scalable manufacturability at low cost. Key efforts will include realization of improved catalysts for the oxygen evolution reaction (OER), fabrication and exploration of MIS photocathode structures using scalable, low-cost, manufacturable approaches and earth-abundant catalyst materials, and an initial adaptation of this approach to MIS structures incorporating III-V semiconductors. Fundamental issues pertaining to the design, fabrication, operation, and properties of MIS photoanodes and photocathodes for solar-driven water-splitting will be elucidated. The materials science and nanoscale properties of thin-film reactions involving metallization layers, insulating oxides, and an underlying semiconductor substrate will be explored, in a context very different from their traditional application in semiconductor micro- and nanoelectronics. New approaches for fabrication of localized nanoscale catalyst structures integrated with thick protective oxides and an underlying semiconductor will be developed. The interplay among buried junction design and structure within the semiconductor, transport of photo-generated minority carriers, and spatial distribution of catalyst islands and conductive paths through a protective oxide layer will be explored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.