Stable Semiconductor Liquid Junction Cell with 9 Percent Solar-to-Electrical Conversion Efficiency

We demonstrate a new type of monolithic tandem junction solar cell. The cell is made up of a bottom (low energy gap) Schottky barrier and a top (high energy gap) semiconductor-electrolyte junction. By using silicon as the low gap and cadmium selenide as the high gap semiconductor we chose a pair of semiconductors which produces equal photocurrents when stacked on top of each other. We have observed open-circuit voltages up to 1.21V which demonstrate addition of the output voltage of the two cells. Short-circuit currents are low, reflecting the poor quality of the CdSe film.The energy bandgap of the absorbing semiconductor chosen for a solar cell represents a compromise for high photocurrent (suggesting a small gap) and high photovoltage (suggesting a large gap) (1). Tandemand higher multiple-junction solar cells improve this compromise by employing in series two or more absorbing semiconductors that cover a range of energy gaps (2). To maximize efficiency and to provide a single output voltage such cells are arranged in electrical series. Tandem cell configurations comprise either two physically separate cells which receive separate portions of the solar spectrum from a dichroic mirror (a spectrum-splitting filter) (3), or a monolithic structure whose top cell absorbs the short wavelength portion of sunlight and transmits the long wavelength portion to the lower cell (4).Series connection of the two cells requires balancing of the photocurrents produced by each individual cell. This requirement makes the two energy gaps depend on each other. The use of semiconductor alloys (3) provides flexibility in the choice of energy gaps, but requires expensive fabrication technology which can be justified only for high performance concentrators.The theoretical principles of tandem solar cells have been analyzed by several authors (5, 6). However, few experimental tests of tandem cells have been reported. It is difficult to find and to combine semiconductors with acceptable photovoltaic properties and whose bandgaps are well matched.In this paper we demonstrate a tandem cell with CdSe (Eg : 1.73 eV) and Si (Eg ~_ 1.12 eV). At Air Mass 1 insolation, the photon flux with hv ~ 1.73 eV is 1.3 • 1017 cm-~ sec-1 and with h~ ~ 1.12 eV, 2.7 • 10 l~ em -2 sec -1. Thus the photon currents absorbed in the two partners of a monolithic CdSe/Si structure are nearly equal, Therefore, the CdSe/Si combination lies close to the point of maximum attainable efficiency for monolithic tandem cells. This semiconductor combination provides a near-ideal vehicle for a highly efficient tandem cell without the expense of alloy semiconductors. Since polycrystalline n-CdSe photoanodes have" been demonstrated with promising efficiency (7), the n-CdSe/n-Si tandem photoanode is an interesting candidate for use in an efficient regenerative photoelectrochemical cell. The observed high output voltage also suggests application in a photoelectrochemical storage cell (8); the voltages developed by most photoelectrochemical cells are insufficient to drive the desi...

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“…5) in agreement with an earlier report (18). Illumination (solid curve) reveals the poor performance of the CdSe film.…”

Section: Fig 3 Photovoltaic I-v Carve Of a Carbon/electrolyte/n-cdssupporting

confidence: 92%

An n ‐ CdSe / SnO2 / n ‐ Si Tandem Electrochemical Solar Cell

Gobrecht

Potter

Nottenburg

et al. 1983

J. Electrochem. Soc.

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“…A number of authors have studied the kinetics of chlorine evolution on RuO2-based electrodes (4-10). The low-slope linear Tafel behavior up to very high anodic current densities has been generally reported for the latter reaction on pure RuO2 film electrodes as well as on mixed RuO2-TiO2 electrodes containing at least 20 mole percent (m/o) of RuO2 (7). However, apparently, some disagreement exists about the mechanism of this reaction and the nature of the rate-determining step (8,10).…”

Section: Introductionmentioning

confidence: 91%

“…Sulfide-polysulfides, telluride-polytellurides, or selenide-polyselenides (7,8) in the electrolyte or ultrathin noble-metal layers deposited onto the semiconductor electrode (6) have, with some success (7), been applied to reduce photocorrosion of the electrode surface.…”

mentioning

confidence: 99%

Hole Reactions from d‐Energy Bands of Layer Type Group VI Transition Metal Dichalcogenides: New Perspectives for Electrochemical Solar Energy Conversion

Tributsch

1978

J. Electrochem. Soc.

215

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Holes, photogenerated in d‐energy bands of covalent semiconducting layer‐type group VI ‐transition metal dichalcogenides react electrochemically differently from holes generated in semiconductors with valence bands based on p‐orbitals (e.g., normalCdS , normalZnO , normalCdSe , normalGaAs ). They do not constitute broken crystal bonds and do therefore not lead directly to an anodic photodecomposition of the electrode. The chemical character of these holes as missing d‐electrons, on the other hand, gives rise to very specific electrochemical surface reactions with electron donors such as I−, Br−, and even OH−, for example. The specific nature of the interfacial charge transfer complexes formed, their advantageous effect on the potential distribution in the electrode surface, and their favorable oxidation potential (in the case of the photoreaction with OH− ions), respectively, may be the clue to a promising new approach to several unaccomplished goals of photoelectrochemical research, among them the construction of stable regenerative electrochemical solar cells and the oxidation of water with visible light. Photoelectrochemical measurements performed with MoSe2 single crystals as well as experiments on solar energy conversion and photoelectrochemical reactions with water induced by visible and near infrared light are described as experimental evidence in support of this finding.

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“…Among them, the rutile TiO 2 is white in color, and is thermally and chemically highly stable, so it is often used as a raw material to produce the white color. Since anatase TiO 2 has photoelectric, photocatalyst, and hydrophilic characterestics, [155][156][157][158] it is used in solar cells, disinfection, and surface selfcleaning applications. After anodizing the Ti, the TiO 2 NTs possess amorphous structure.…”

Section: Tio 2 Nanotubesmentioning

confidence: 99%

Fabrication and Characterization of Highly-Ordered Valve-Metal Oxide Nanotubes and Their Derivative Nanostructures

Chen¹,

Dong²,

Luo³

2012

Rev Nanosci Nanotech

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Highly ordered and vertically aligned straight nanotubes can be fabricated using an electrochemical anodization method on the valve metal surfaces, and a variety of nanostructures can be derived from these nanotubes. These nanomaterials have found a wide range of applications, especially in the fields of renewable energy generation and storage. This review provides step-by-step guidelines about the fabrication details and parameters of these nanomaterials, focusing on the systems originated from the metals of Al, Ti and Zr. Based on the fabrication of these nanotubes, different methods were developed to produce uniform metal nanowires using electrodeposition and mechanical injection, nanospheres and nanowhiskers on the top surfaces of the nanotubes, and dye-sensitized solar cells using anodic Ti oxide. These nanostructures and their phase transitions were characterized in detail by X-ray diffraction and electron microscopy techniques. Finally, towards the commercial applications of the nanotube related materials, fabrication of large-scale porous films was proposed.

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Stable Semiconductor Liquid Junction Cell with 9 Percent Solar-to-Electrical Conversion Efficiency

Cited by 108 publications

References 11 publications

An n ‐ CdSe / SnO2 / n ‐ Si Tandem Electrochemical Solar Cell

An n ‐ CdSe / SnO2 / n ‐ Si Tandem Electrochemical Solar Cell

Hole Reactions from d‐Energy Bands of Layer Type Group VI Transition Metal Dichalcogenides: New Perspectives for Electrochemical Solar Energy Conversion

Fabrication and Characterization of Highly-Ordered Valve-Metal Oxide Nanotubes and Their Derivative Nanostructures

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