Surface charge and specific ion adsorption effects in photoelectrochemical devices

Journal Article · Mon Dec 01 04:00:00 EST 1980 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.327616· OSTI ID:6734950

Singh, P; Singh, R; Gale, R; Rajeshwar, K; DuBow, J

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.

• Research Organization: Department of Electrical Engineering, Colorado State University, Fort Collins, Colorado 80523
• OSTI ID: 6734950
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 51:12; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ABSORPTION
ADSORPTION
ALUMINIUM CHLORIDES
ALUMINIUM COMPOUNDS
ARSENIC COMPOUNDS
ARSENIDES
CHARGED PARTICLES
CHLORIDES
CHLORINE COMPOUNDS
DATA
DESIGN
ELECTRIC CHARGES
ELECTROCHEMICAL CELLS
ELECTROLYTES
ELEMENTS
EQUIPMENT
GALLIUM ARSENIDES
GALLIUM COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
INFORMATION
INTERFACES
IONS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHOTOELECTROCHEMICAL CELLS
PHOTOVOLTAIC EFFECT
PNICTIDES
QUANTITY RATIO
SEMIMETALS
SILICON
SOLAR EQUIPMENT
SORPTION
SURFACES