Scientists unlock tenfold mobility boost in copper oxide solar fuel cells
Researchers discovered that copper oxide crystals conduct electricity dramatically better along one crystallographic direction, enabling a new generation of cheap solar-to-fuel converters. The finding addresses a decade-old bottleneck in sustainable hydrogen production and could accelerate commercialization of technology that turns sunlight into storable chemical energy.
Originaltitel: High carrier mobility along the [111] orientation in Cu<sub>2</sub>O photoelectrodes
<p>Solar fuels offer a promising approach to provide sustainable fuels by harnessing sunlight<sup>1,2</sup>. Following a decade of advancement, Cu<sub>2</sub>O photocathodes are capable of delivering a performance comparable to that of photoelectrodes with established photovoltaic materials<sup>3,4,5</sup>. However, considerable bulk charge carrier recombination that is poorly understood still limits further advances in performance<sup>6</sup>. Here we demonstrate performance of Cu<sub>2</sub>O photocathodes beyond the state-of-the-art by exploiting a new conceptual understanding of carrier recombination and transport in single-crystal Cu<sub>2</sub>O thin films. Using ambient liquid-phase epitaxy, we present a new method to grow single-crystal Cu<sub>2</sub>O samples with three crystal orientations. Broadband femtosecond transient reflection spectroscopy measurements were used to quantify anisotropic optoelectronic properties, through which the carrier mobility along the [111] direction was found to be an order of magnitude higher than those along other orientations. Driven by these findings, we developed a polycrystalline Cu<sub>2</sub>O photocathode with an extraordinarily pure (111) orientation and (111) terminating facets using a simple and low-cost method, which delivers 7 mA cm<sup>−2</sup> current density (more than 70% improvement compared to that of state-of-the-art electrodeposited devices) at 0.5 V versus a reversible hydrogen electrode under air mass 1.5 G illumination, and stable operation over at least 120 h.</p>