Heterojunction silicon/indium tin oxide photoelectrodes: development of stable systems in aqueous electrolytes and their applicability to solar energy conversion and storage
An approach to circumvent the problem of poor photoelectrochemical (PEC) stability of Si in aqueous electrolytes is the use of heterojunction photoelectrodes comprising the Si/SiO/sub x// indium tin oxide (ITO) structure. As in a Schottky barrier electrode system, the maximum photovoltage attainable with these electrodes is limited by the barrier height at the Si/ITO heterojunction. Both n- and p-Si substrates have been studied. In regenerative PEC systems designed for the conversion of solar energy to electricity, the efficacy of charge transfer at the ITO/electrolyte interface is shown to be a crucial factor. Of the redox electrolytes tested (S/sup 2 -//S/sup 2 -//sub x/,, I/sup 3 -//I/sup -/, (Fe(CN)/sub 6/)/sup 3-/4-/ and Fe/sup 2+/3+/ EDTA), the (Fe(CN)/sup 6//sup 3-/4-/ couple was by far the most efficient in terms of charge transfer across the ITO/electrolyte interface. Optical-to-electrical conversion efficiencies (eta) of 1.57% and 5.7% (approx. AM 1 illumination) were attained for PEC cells based on n- and p-Si substrates, respectively. Detailed tests have revealed long-term stability in (Fe(CN)/sub 6/)/sup 3-/4-/ electrolytes once the ITO film thickness (greater than or equal to 50 A) and solution pH (approx. 12 to 14) were optimized, n-Si/ITO electrodes were used for the photooxidation of Cl/sup -/ from concentrated LiCl and NaCl electrolytes to illustrate the chemical inertness and stability of these electrodes. Catalytic modification of the ITO surface with RuO/sub 2/ was found to be necessary to sustain Cl/sub 2/ production. Values of eta up to 2.7% were recorded with this PEC system at 100 mW/cm/sup 2/. Finally, the applicability of Si/ITO heterojunction electrodes for the photoassisted splitting of water was demonstrated. Preliminary experiments have revealed a 40% reduction in the threshold voltage required for water photolysis. Catalytic modification of the ITO surface was again a prerequisite for efficient performance of these electrodes.
- Research Organization:
- Colorado State Univ., Fort Collins
- OSTI ID:
- 6204289
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 105:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ELECTROLYTES
REGENERATION
PHOTOELECTROCHEMICAL CELLS
OPTIMIZATION
PLATINUM
CATALYTIC EFFECTS
RUTHENIUM OXIDES
WATER
PHOTOLYSIS
EFFICIENCY
INDIUM OXIDES
N-TYPE CONDUCTORS
P-TYPE CONDUCTORS
PH VALUE
PHOTOANODES
PHOTOCATHODES
REACTION KINETICS
REDOX REACTIONS
SILICA
SILICON
SOLAR CELLS
SOLAR ENERGY CONVERSION
STABILITY
TIN OXIDES
ANODES
CATHODES
CHALCOGENIDES
CHEMICAL REACTIONS
CONVERSION
DECOMPOSITION
DIRECT ENERGY CONVERTERS
ELECTROCHEMICAL CELLS
ELECTRODES
ELEMENTS
ENERGY CONVERSION
EQUIPMENT
HYDROGEN COMPOUNDS
INDIUM COMPOUNDS
KINETICS
MATERIALS
METALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PLATINUM METALS
RUTHENIUM COMPOUNDS
SEMICONDUCTOR MATERIALS
SEMIMETALS
SILICON COMPOUNDS
SILICON OXIDES
SOLAR EQUIPMENT
TIN COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)