Effect of Grain Boundary Cross-Section on the Performance of Electrodeposited Cu2O Photocathodes
- Authors
- Publication Date
- Dec 03, 2018
- Identifiers
- DOI: 10.1002/2014GL061265
- OAI: oai:dsapce.library.iitb.ac.in:100/24985
- Source
- DSpace at IIT Bombay
- Keywords
- License
- Unknown
- External links
Abstract
Large-grained Cu2O photocathodes in a superstrate configuration on a F-doped SnO2 (FTO) coated glass substrate are synthesized via two-step electrodeposition. Only submicrometer sized grains were obtained during single-step electrodeposition in the potential window (-0.31 to -0.7 V vs Ag/AgCl) of stable Cu2O formation. We observe reductive decomposition of the Cu2O to Cu metal in the potential range of -0.7 to -0.98 V; bulk reduction of Cu2+ in the solution to Cu metal occurs only beyond -0.98 V. In the potential window of stable Cu2O deposition, only the growth of the few nuclei occurs until a certain time. Minimal nucleation on the pristine FTO sites occurs during this period of deposition. The time to secondary nucleation is similar to 6 min at -0.31 V and similar to 15 s at -0.37 V. Interrupting the deposition at -0.31 V after 6 min and increasing the potential to -0.37 V leads to uniform, large grains (similar to 3 mu m) of Cu2O. Photoinduced conducting atomic force microscopy reveals shunting and the presence of sub-bandgap states at the grain boundaries of Cu2O. Also, the lower carrier concentration (similar to 1016 cm(-2)) in the large-grained Cu2O film obtained from Mott-Schottky analysis suggests a lower rate of Auger recombination. Thus, lowering the grain boundary cross-section in the two-step deposited film leads to a 30% increase in photocurrent at 0.0 V vs RHE.
