Concentrated Radiation for Low-Temperature and High-Temperature Solar Water and CO₂ Reduction Devices

Solar-driven approaches for the processing of solar fuels and materials are interesting, provided they can be efficiently, stably, scalably, and sustainably implemented. Especially photon-driven water splitting or CO₂ reduction has gained some attention. One way to increase the economic and sustainable competitiveness is the utilization of concentrated irradiation [1]. This pathway can also justify the utilization of rarer materials, given their significantly reduced area and material need.<br/>Here, I will discuss room-temperature operation of concentrated photoelectrochemical devices for water splitting [1] and CO₂ reduction, highlighting the requirements on the photoabsorber performance and their best integration into an operational electrochemical device. I will then extend the discussion to photon-driven devices that operate at significantly higher temperatures (&gt; 700 K) making use of a larger part of the solar spectrum and profiting from significantly enhanced kinetics [2]. Such devices require novel semiconductor-junctions that allow for effective charge separation. Specifically, we identify assemblies of GaAs/GaP and GaAs/GaInP-GaAs/GaP as potential candidates for such high-temperature solar cells. I will discuss how they can be best integrated into an operational high-temperature photoelectrochemical device, and compare their performance and potential with low-temperature approaches.<br/><b>References</b><br/>[1] S. Tembhurne, F. Nandjou, S. Haussener, <i>Nature Energy</i>, 10.1038/s41560-019-0373-7, 2019.<br/>[2] R. Gutierrez, S. Haussener, <i>Sustainable Energy & Fuels</i>, 10.1039/D0SE01749C, 2021.