Effect of microscopic discontinuity of metal overlayers on the photovoltages in metal-coated semiconductor-liquid junction photoelectrochemical cells for efficient solar energy conversion

Journal Article · Thu Apr 21 04:00:00 EDT 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100319a043· OSTI ID:7247021

Nakota, Y; Ueda, K; Yano, H; Tsubomura, H

The open-circuit photovoltage V/sub oc/ of a photoelectrochemical cell equipped with a platinum-coated n-Si semiconductor electrode remarkably increased when the Pt layer was made microscopically discontinuous. A strikingly high V/sub oc/ of 0.685 V has been obtained for a Pt-coated and alkali-etched n-Si electrode in which Pt existed in the form of islands 5-20 nm wide. The V/sub oc/ is much higher than those for normal p-n-junction Si solid solar cells (about 0.59 V). This is an encouraging result, which possibly makes a novel approach to highly efficient solar cells. Theoretical considerations on the effect of the discontinuity of the metal overlayers in metal-coated electrodes have shown that high photovoltages can be generated in cases where the metal exists in the form of extremely small, sparsely scattered islands, say about 5 nm wide, separated by about 20 nm from each other, even though no increase in the intrinsic barrier height at the metal-islandsemiconductor interface is assumed to occur. The effective barrier height at the semiconductor-liquid junction can increase to the equivalent of the band gap by choosing appropriate redox couples due to the rapid decay of the potential modulation near the metal-islandsemiconductor interface. In silicon electrodes covered with minute metal islands, the naked parts of the silicon surface are covered with insulating thin oxide layers, and the metal-covered parts serve as gates for the carrier transport. Accordingly, the saturation current can become quite low because most of the silicon surface is covered with the oxide layer, producing only low densities of intragap states, and the surface recombination at these parts becomes negligibly slow.

• Research Organization: Osaka Univ. (Japan)
• OSTI ID: 7247021
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 92:8; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501 -- Solar Energy Conversion-- Photovoltaic Conversion
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
400500* -- Photochemistry
COATINGS
CONVERSION
CURRENTS
DATA
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELEMENTS
ENERGY CONVERSION
EQUIPMENT
EXPERIMENTAL DATA
INFORMATION
MATERIALS
METALS
N-TYPE CONDUCTORS
NUMERICAL DATA
PHOTOCONDUCTIVITY
PHOTOCURRENTS
PHOTOELECTROCHEMICAL CELLS
PHYSICAL PROPERTIES
PLATINUM
PLATINUM METALS
SEMICONDUCTOR MATERIALS
SEMIMETALS
SILICON
SOLAR ENERGY CONVERSION
SOLAR EQUIPMENT
TRANSITION ELEMENTS