Photoinduced layer phenomenon caused by iodine formation in MoSe2: electrolyte (iodide) junctions
✍ Scribed by H. Tributsch; T. Sakata; T. Kawai
- Publisher
- Elsevier Science
- Year
- 1981
- Tongue
- English
- Weight
- 549 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0013-4686
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✦ Synopsis
When iodide isphotooxidized at a n-type MoSe, electrode ata high rate, a dim film is observed to spread over the metallic bright electrode and the reflected light intensity throughout the visible and near it spectral region drops by 70-80% . The phenomenon can -in a reversible way -be controlled by small potential variations (0 -+0 .5 V) and beyond + 1 .0 V produces clcetrochemical oscillations, which are paralleled by an additional reflection change which can be seen to propagate across the electrode surface .
The phenomenon could be reproduced in absence of light at semiconducting p-type MoSe" at metallic NbSe, and at Pt-electrodes which excluded the possibility that the pronounced optical changes are produced by a photoelectrochemical or electrochemical modification of layer-type electrode material in presence of iodide . The reflection anomalies can be explained by physical properties of an iodine layer, which is formed in the iodide-depleted diffusion region at the electrode surface .
Evidence is given that the spreading of the dim film is actually a phase transition from dispersed to crystalline iodine with an asymmetrical size distribution within the Idepleted diffusion layer . The resulting gradient of the refraction index works like an anti-reflecting coating . The described phenomenon will have to be considered in attempts to optimize solar cells based on the I -/1, redox couple and it might be of some practical interest for antireflecting layer-technology and clectro-optical applications .