A Novel Strategy for High Performance Cost-Competitive Solar Water Splitting Enabled with Integrated Bifacial GaAs Photoelectrodes

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Solar-powered production of hydrogen from water offers the potential to enable solar power, which is available on a transient basis, to be stored in the form of a chemical fuel. This capability would allow the energy to be stored temporarily, then deployed during times of high demand but relatively low availability of sunlight. Efficient and cost-effective solar-powered production of hydrogen from water remains a scientific and technological challenge with issues of efficiency, cost, and materials durability. This project will investigate fundamental concepts from the field of semiconductor electronics to enable new approaches to make efficient, low-cost photoelectrodes for splitting water molecules into hydrogen and oxygen using the energy in sunlight. Among materials systems considered, III-V compound semiconductors represent one of the most promising materials for high efficiency solar-driven water splitting due to excellent materials properties pertaining to their favorable interaction with sunlight and efficient photocarrier generation. This fundamental research project aims to develop a high performance, cost-competitive materials platform for III-V photoelectrodes that can address the technology challenges. The multidisciplinary themes of the research will be integrated with the PI's comprehensive teaching and outreach efforts including training for undergraduate and graduate student researchers with a special emphasis on broadening participation of students from underrepresented groups in STEM, as well as summer educational program for educationally-disadvantaged high school students. The scientific and engineering advances achieved in this project will contribute to the continuing efforts to make the technology of solar hydrogen generation cost-effective and therefore address the future energy demand of society. The goal of this research project is to explore novel strategies for III-V compound semiconductor photoelectrodes that can address fundamental challenges in cost and durability. The electrode design and fabrication strategies would relax the stringent materials requirements at the semiconductor/electrolyte interface in ways that provide unique pathways to improve their stability, while allowing substantial reduction in materials cost. To achieve this goal, the project will (1) research a novel materials platform of III-V photoelectrodes based on printed assemblies of ultrathin GaAs-based epitaxial materials, (2) study at a fundamental level the photoelectrochemical behaviors of integrated bifacial GaAs photoelectrodes in solar-driven water splitting at the semiconductor/electrolyte interface, (3) establish design criteria and fundamental understanding of charge separation and transport, electronic band configuration, and photonic enhanced light absorption, (4) explore novel passivation mechanisms using optically thick metals and metal oxides, and (5) investigate integration pathways to tandem systems for unassisted solar water splitting through strategic assemblies of interconnected GaAs photoelectrodes. The outcomes of the project will provide a firm foundation for fundamental understanding of photoelectrochemical water splitting processes with ultrathin GaAs nanomembrane photoelectrodes, and elucidate mechanisms of performance- and stability enhancements by synergistic contributions from specialized epitaxial design, nanoscale photon management, and bifacial electrode configuration. Techniques of transfer printing for deterministic materials assembly will expand materials options in the design of efficient solar water splitting systems but also provide diverse integration pathways for enhanced cost-effectiveness, system performance, and stability.