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Title: Surface charge and specific ion adsorption effects in photoelectrochemical devices

Abstract

The importance of specific ion adsorption and surface charge effects in the design and operation of photoelectrochemical (PEC) devices is demonstrated by experimental data on the n-GaAs/electrolyte and n-Si/electrolyte interface. The electrolyte chosen for the present study was an ambient temperature molten salt comprising mixtures of aluminum chloride and n-butyl pyridinium chloride in varying molar ratios. A direct correlation between specific adsorption effects and photovoltaic output parameters is presented for the n-GaAs PEC system. Evidence for specific adsorption of Cl/sup -/ ions in this system is found in the systematic shift observed in flat-band potentials V/sub fb/ towards negative values with increasing concentration of free Cl/sup -/ ions in the AlCl/sub 3/-BPC electrolyte. The magnitude of the slope of V/sub fb/ versus pCl (=-log(Cl/sup -/)) plots (approx.0.13 V or 2(2.3kT/q) V) is consistent with that expected from Esin-Markov adsorption behavior. Anomalous PEC behavior is observed at the n-Si/AlCl/sub 3/-BPC interface brought about by modifications in electrostatics across the electrode/electrolyte interphasial region. These modifications arise from either specific adsorption effects or by electrodeposition of aluminum on the n-Si electrode surface. Either process results in a net lowering of the band structure in n-Si on the energy scale relative to the redoxmore » levels. An examination of literature data on high-efficiency PEC systems reveals that similar shifts in the relative positions of the semiconductor energy levels and redox energies may play an important role in ensuring a more favorable photoresponse than that predicted from idealized models.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Department of Electrical Engineering, Colorado State University, Fort Collins, Colorado 80523
OSTI Identifier:
6734950
DOE Contract Number:  
XP-9-8002-9
Resource Type:
Journal Article
Journal Name:
J. Appl. Phys.; (United States)
Additional Journal Information:
Journal Volume: 51:12
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; PHOTOELECTROCHEMICAL CELLS; ABSORPTION; ADSORPTION; ALUMINIUM CHLORIDES; DATA; DESIGN; ELECTRIC CHARGES; ELECTROLYTES; GALLIUM ARSENIDES; INTERFACES; IONS; ORGANIC CHLORINE COMPOUNDS; PHOTOVOLTAIC EFFECT; QUANTITY RATIO; SILICON; SURFACES; ALUMINIUM COMPOUNDS; ARSENIC COMPOUNDS; ARSENIDES; CHARGED PARTICLES; CHLORIDES; CHLORINE COMPOUNDS; ELECTROCHEMICAL CELLS; ELEMENTS; EQUIPMENT; GALLIUM COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; INFORMATION; ORGANIC COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; PNICTIDES; SEMIMETALS; SOLAR EQUIPMENT; SORPTION; 140505* - Solar Energy Conversion- Photochemical, Photobiological, & Thermochemical Conversion- (1980-)

Citation Formats

Singh, P, Singh, R, Gale, R, Rajeshwar, K, and DuBow, J. Surface charge and specific ion adsorption effects in photoelectrochemical devices. United States: N. p., 1980. Web. doi:10.1063/1.327616.
Singh, P, Singh, R, Gale, R, Rajeshwar, K, & DuBow, J. Surface charge and specific ion adsorption effects in photoelectrochemical devices. United States. doi:10.1063/1.327616.
Singh, P, Singh, R, Gale, R, Rajeshwar, K, and DuBow, J. Mon . "Surface charge and specific ion adsorption effects in photoelectrochemical devices". United States. doi:10.1063/1.327616.
@article{osti_6734950,
title = {Surface charge and specific ion adsorption effects in photoelectrochemical devices},
author = {Singh, P and Singh, R and Gale, R and Rajeshwar, K and DuBow, J},
abstractNote = {The importance of specific ion adsorption and surface charge effects in the design and operation of photoelectrochemical (PEC) devices is demonstrated by experimental data on the n-GaAs/electrolyte and n-Si/electrolyte interface. The electrolyte chosen for the present study was an ambient temperature molten salt comprising mixtures of aluminum chloride and n-butyl pyridinium chloride in varying molar ratios. A direct correlation between specific adsorption effects and photovoltaic output parameters is presented for the n-GaAs PEC system. Evidence for specific adsorption of Cl/sup -/ ions in this system is found in the systematic shift observed in flat-band potentials V/sub fb/ towards negative values with increasing concentration of free Cl/sup -/ ions in the AlCl/sub 3/-BPC electrolyte. The magnitude of the slope of V/sub fb/ versus pCl (=-log(Cl/sup -/)) plots (approx.0.13 V or 2(2.3kT/q) V) is consistent with that expected from Esin-Markov adsorption behavior. Anomalous PEC behavior is observed at the n-Si/AlCl/sub 3/-BPC interface brought about by modifications in electrostatics across the electrode/electrolyte interphasial region. These modifications arise from either specific adsorption effects or by electrodeposition of aluminum on the n-Si electrode surface. Either process results in a net lowering of the band structure in n-Si on the energy scale relative to the redox levels. An examination of literature data on high-efficiency PEC systems reveals that similar shifts in the relative positions of the semiconductor energy levels and redox energies may play an important role in ensuring a more favorable photoresponse than that predicted from idealized models.},
doi = {10.1063/1.327616},
journal = {J. Appl. Phys.; (United States)},
number = ,
volume = 51:12,
place = {United States},
year = {1980},
month = {12}
}