High carrier mobility along the [111] orientation in Cu<sub>2</sub>O photoelectrodes.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38658685.
- Also identified by DOI 10.1038/s41586-024-07273-8 and PMC identifier 11043049.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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>3-5</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.