Photoelectrochemistry and heterogeneous photo-catalysis at semiconductors

Nanometer-sized particles of the chalcopyrite compounds CuInS2 and CuInSe2 were synthesized by thermal decomposition of molecular single-source precursors (PPh3)2CuIn(SEt)4 and (PPh3)2CuIn(SePh)4, respectively, in the noncoordinating solvent dioctyl phthalate at temperatures between 200 and 300 °C. The nanoparticles range in size from 3 to 30 nm and are aggregated to form roughly spherical clusters of about 500 nm in diameter. X-ray diffraction of the nanoparticle powders shows greatly broadened lines, indicative of very small particle sizes, which is confirmed by TEM. Peaks present in the XRD can be indexed to reference patterns for the respective chalcopyrite compounds. Optical spectroscopy and elemental analysis by energy dispersive spectroscopy support the identification of the nanoparticles as chalcopyrites.

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Nanocrystalline Chalcopyrite Materials (CuInS2 and CuInSe2) via Low-Temperature Pyrolysis of Molecular Single-Source Precursors

A review of chemically modified carbon paste electrodes (CMCPEs) and their use in voltammetric analysis is presented. The different methods of modification as well as the types of interaction between substrate and modifier are discussed. In addition to a survey of the literature (173 references), the scope of and prospects in this field of electroanalysis are discussed briefly.

Chemically modified carbon paste electrodes in voltammetric analysis

The development of photoelectrochemical solar cells based on semiconductor liquid junctions is discussed. Over the past 6 years, the efficiency of solar energy conversion has increased from < 1% to 12%, and the operational life of these cells has increased from hours to months. Understanding the chemistry of surfaces and grain boundaries has made it possible to manipulate the position of the surface and grain boundary states and thus reduce losses due to electron-hole recombination. Cells exhibiting approx. 12% efficiency of conversion are: (1) chemisorbed Ru/sup 3 +/ ions on n-GaAs photoanodes; (2) diffused Ru/sup 3 +/ and Pb/sup 2 +/ into grain boundaries of polycrystalline n-GaAs films on graphite; (3) p-InP/VCl/sub 3/-VCl/sub 2/-HCl/C cell; and (4) p-InP(Ru)/HCl-KCl/Pt cell. Photoassisted electrolysis of water for conversion of solar energy to hydrogen using the last mentioned photoelectrochemical cell represents the most efficient system for solar energy conversion. 61 references are cited. (BLM)tic stainless steel is required to prevent stress corrosion cracking byd stuffs contamination in the USSR takes place in the framework of variations observed in separate countries of northern hemisphere.

Conversion of Sunlight into Electrical Power and Photoassisted Electrolysis of Water in Photoelectrochemical Cells

Ke Sun,† Shaohua Shen,*,‡,§ Yongqi Liang, Paul E. Burrows, Samuel S. Mao,* and Deli Wang*,†,⊥,# †Department of Electrical and Computer Engineering, Material Science Program, and QualComm Institute, University of California at San Diego, La Jolla, California 92093, United States ‡International Research Center for Renewable Energy, State Key Lab of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720, United States Department of Chemistry, Chemical Biological Center, Umea ̊ University, Linnaeus vag̈, 6 901 87 Umea,̊ Sweden Samuel Mao Institute of New Energy, Science Hall, 1003 Shangbu Road, Shenzhen, 518031, China

Enabling silicon for solar-fuel production

Pressure sintered electrodes of cadmium selenide subsequently doped with cadmium vapor have shown solar energy conversion efficiencies approaching /sup 3///sub 4/ of those of single crystal specimens in sunlight experiments. The cell CdSe/1F Na/sub 2/S-1F S-1F NaOH/C has operated at 5.1% conversion efficiency under AM2 conditions with polycrystalline electrodes. The relatively small sacrifice of efficiency from single crystal values of 7.5 +- 0.5% suggests the possibility of substantial cost advantage. The temperature and pressure conditions, cadmium doping procedure, material characterization, and the voltammetric behavior of the cell are discussed.

Solar Conversion Efficiency of Pressure Sintered Cadmium Selenide Liquid Junction Cells

CuInS2 Liquid Junction Solar Cells

Output Stability of n-CdSe/Na2S-S-NaOH/C Solar Cells

Anodic formation of semiconductive sulfide films at cadmium and bismuth. Rotating ring-disk electrode studies

Voltammetric and light to electrical energy conversion characteristics of metallized semiconductor Schottky junctions with redox solution contacts are reported. Electrodeposited noble metal films on establish contacts to reversible aqueous redox couple solutions that can sustain solar photocurrent levels with low loss, requiring only a thin metal layer adequate to photovoltaic barrier formation. Possible advantages in lateral conductivity, relative to solid‐state Schottky devices, and in surface stability and redox electrolyte independence, relative to semiconductor‐liquid junction solar cells, are weighed against both the absorptive losses in the metal layer and the practicalities of obtaining sufficient integrity in the film to serve the semiconductor corrosion protection function. Gold, platinum, and rhodium plated with carbon counter‐electrodes and ferro‐ferricyanide solutions give 2–6% conversion efficiency under solar irradiance.

S. Menezes

Papers

Solar Conversion Efficiency of Pressure Sintered Cadmium Selenide Liquid Junction Cells

CuInS2 Liquid Junction Solar Cells

Output Stability of n-CdSe/Na2S-S-NaOH/C Solar Cells

Anodic formation of semiconductive sulfide films at cadmium and bismuth. Rotating ring-disk electrode studies

Metal Filmed‐Semiconductor Photoelectrochemical Cells