Journal
ADVANCED ENERGY MATERIALS
Volume 2, Issue 9, Pages 1109-1116Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.201100728
Keywords
semiconductors; composites; electrodes; electro-optical materials
Categories
Funding
- National Science Foundation (NSF) Center for Chemical Innovation [CHE-0802907]
- DARPA
- NSF [CHE-1042006]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [0802907] Funding Source: National Science Foundation
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1042006] Funding Source: National Science Foundation
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Gallium phosphide exhibits a short diffusion length relative to its optical absorption length, and is thus a candidate for use in wire array geometries that allow light absorption to be decoupled from minority carrier collection. Herein is reported the photoanodic performance of heteroepitaxially grown gallium phosphide on planar and microwire-array Si substrates. The n-GaP|n-Si heterojunction results in a favorable conduction band alignment for electron collection in the silicon. A conformal electrochemical contact to the outer GaP layer is produced using the ferrocenium/ferrocene (Fc+/Fc) redox couple in acetonitrile. Photovoltages of similar to 750 mV under 1 sun illumination are observed and are attributed to the barrier formed at the (Fc+/Fc)|n-GaP junction. The short-circuit current densities of the composite microwire-arrays are similar to those observed using single-crystal n-GaP photoelectrodes. Spectral response measurements along with a finite-difference-time-domain optical model indicate that the minority carrier diffusion length in the GaP is similar to 80 nm. Solid-state currentvoltage measurements show that shunting occurs through thin GaP layers that are present near the base of the microwire-arrays. The results provide guidance for further studies of 3D multi-junction photoelectrochemical cells.
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