Detailed investigation of the role of surface motifs on the behavior of p-wse2 photocathodes

Velazquez, J. M. et al. A Scanning Probe Investigation of the Role of Surface Motifs in the Behavior of p–WSe2Photocathodes. Energy & Environmental Science, DOI: 10.1039/C5EE02530C (2015).


Scientific Achievement

Detailed investigation of microscopic terraces in p–WSe2 single-crystal photocathode revealed these to be major sites of performance losses, challenging the traditionally accepted paradigm of edges as the sole source of deleterious electron-hole recombination.

 

Significance & impact

This study elucidates the structure-property-performance relationships of p-WSe2 photocathodes and provides valuable information on guiding the design of more efficient photoelectrodes from single crystals or thin films.

  Image created by Dr. Kyle Cummins (JCAP). The schematic shows an external quantum yield (Φext) map overlaid on a p–WSe2 topography exhibiting step edges and terrace sites.  In a typical experiment, an incident laser (λ=533 nm) probes bare and platinum decorated sites.  The bare terraces that had low Φext,533 (< 0.15) values showed sub-bandgap states, whereas this feature was not observed on terraces that exhibited high Φext,533 (> 0.30).

 

Image created by Dr. Kyle Cummins (JCAP).

The schematic shows an external quantum yield (Φext) map overlaid on a p–WSe2 topography exhibiting step edges and terrace sites.  In a typical experiment, an incident laser (λ=533 nm) probes bare and platinum decorated sites.  The bare terraces that had low Φext,533 (< 0.15) values showed sub-bandgap states, whereas this feature was not observed on terraces that exhibited high Φext,533 (> 0.30).

Research Details

  • p–WSe2 single crystals were synthesized by chemical vapor-transport method.
  • Scanning photocurrent microscopy under relevant electrochemical environments was used to spatially differentiate performance at the microscale.
  • The relationship between surface topography and performance was studied by a suite of ex situscanning probe techniques.

Contact: nslewis@caltech.edu

 

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