To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.

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Visible-Light Photocatalysis in Nitrogen-Doped Titanium Oxides

TiO2 photocatalysis and related surface phenomena

A thin‐film, two‐layer organic photovoltaiccell has been fabricated from copper phthalocyanine and a perylene tetracarboxylic derivative. A power conversion efficiency of about 1% has been achieved under simulated AM2 illumination. A novel feature of the device is that the charge‐generation efficiency is relatively independent of the bias voltage, resulting in cells with fill factor values as high as 0.65. The interface between the two organic materials, rather than the electrode/organic contacts, is crucial in determining the photovoltaicproperties of the cell.

Two‐layer organic photovoltaic cell

Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Understanding TiO2 photocatalysis: mechanisms and materials.

Photoinduced reactivity of titanium dioxide

In all previous studies of the photoelectrolysis of water, very little attention has been paid to the carrier generation and transport properties of the optically active semiconductor electrode To gather such information the present work theoretically analyzes the spectral response of TiO/sub 2/ photoelectrolysis cells Comparison with experimental results allows us to determine the diffusion length of minority carriers in TiO/sub 2/ for the first time It is the hole transport that governs the spectral response curve, not the electron transport The quantum efficiency of carrier generation in TiO/sub 2/ electrodes in the photolysis mode can be increased to 80% by doping the crystals with Al The sunlight conversion efficiency has been raised to 13% from 04% reported earlier by others The spectral response of the device has been extended into the visible portion of the spectrum through sensitization of the TiO/sub 2/ with Cr dopant impurities, allowing hydrogen generation with visible light The photoelectrolytic processes associated with the impurity doped crystals are discussed 36 references

Photoelectrolysis of water in sunlight with sensitized semiconductor electrodes

Photocatalytic decomposition of water at semiconductor electrodes

Recently, we reported on the development of a new thin‐film organic solar cell with an AM1 sunlight efficiency of about 0.7% for large area devices (∼1 cm2). This relatively high‐efficiency MIS‐Schottky barrier‐type cell was based on merocyanine type photosensitizing dyes. In this paper we present additional experimental results and develop a comprehensive theoretical model to explain the observed photovoltaic properties. The model incorporates the generation, transport, and surface dissociation of excitons and field‐dependent quantum efficiency. The low fill factor of 0.3 was attributed mainly to the field dependence of quantum efficiency. An exciton diffusion length of 60 A was determined by analyzing the short‐circuit photocurrent action spectra using the theoretical model developed. The diffusion potentials for metal/merocyanine Schottky barrier cells for six different metals were determined by C‐V measurements; the diffusion potential increases with decreasing work function. As solar cells, these dev...

Merocyanine organic solar cells

The photovoltaic and rectification properties of Al/Mg phthalocyanine/Ag sandwich cells are reported. At low voltages, the current in the forward direction varies exponentially with voltage. A charge density of [inverted lazy s]1018/cm3 is estimated from C‐V measurements. The short‐circuit photocurrent JscαFm (m [inverted lazy s]0.5), where F is the incident light intensity. The open‐circuit photovoltage Vocα logF as expected for a Schottky barrier or p‐n junction. The J‐V curve in the photovoltaic mode is characteristic of a cell with large series resistance. From the photovoltaic action spectra, the electron diffusion length is estimated to be [inverted lazy s]1.5×10−6 cm. The action spectrum is dependent on the direction of the incident radiation. A theory is presented which explains the results. The junction is attributed to a Schottky barrier of Vd ∼ 0.6 eV and width ∼ 2.5 × 10−6 cm estimated from C‐V measurement. The values determined from photovoltaic measurements are in agreement. The lifetime of ...

Photovoltaic and rectification properties of Al/Mg phthalocyanine/Ag Schottky‐barrier cells

Grain boundary states play a dominant role in determining the electrical and photovoltaic properties of polycrystalline silicon by acting as traps and recombination centers. The recombination loss at grain boundaries is the predominant loss mechanism in polycrystalline solar cells. Cell parameters are calculated based on a transformation of grain boundary recombination centers to a uniform distribution of such states throughout the grain. Effective carrier lifetime is expressed in terms of grain size, allowing calculation of short‐circuit current, open‐circuit voltage, and fill factor. Excellent agreement is observed between theory and experiment for almost all device parameters. It is indicated that one could fabricate 10% efficiency polycrystalline solar cells from 20‐μm‐thick material if the grain size exceeds 500 μm.

Amal K. Ghosh

Papers

Photoelectrolysis of water in sunlight with sensitized semiconductor electrodes

Photocatalytic decomposition of water at semiconductor electrodes

Merocyanine organic solar cells

Photovoltaic and rectification properties of Al/Mg phthalocyanine/Ag Schottky‐barrier cells

Theory of the electrical and photovoltaic properties of polycrystalline silicon