Excited-state processes of relevance to photoelectrochemistry

Ellis, Arthur B.

doi:10.1021/ed060p332

Cited by 11 publications

(7 citation statements)

References 17 publications

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“…A dead-layer model which quantifies PL quenching in the solid-state systems has recently been found applicable to PEC's based on n-CdSe and n-GaAs (4,5). [2] -exp (-ED) [2] (~rFB where D is the dead-layer thickness; (br and (~rFB are the radiative quantum efficiencies at an in-circuit potential and at flatband potential (approximated here as the open-circuit potential); and ~' = ~ + fl with ~ and fl the solid's absorptivities for the exciting and emitted light, respectively. The mathematical form of the model is given by EQ.…”

Section: Pec Properties--althoughmentioning

confidence: 99%

Zinc Selenide Photoelectrodes: Efficient Radiative Recombination in a Stable Photoelectrochemical Cell

Smiley

Biagioni

Ellis

1984

J. Electrochem. Soc.

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Photoluminescence (PL) and electroluminescence (EL) from single-crystal, n-type, Al-doped ZnSe (ZnSe:A1) electrodes have been studied. These samples exhibit both edge emission (k~a~ ~ 460 nm) and subbandgap emission when excited at several ultrabandgap wavelengths. The latter PL band is particularly intense, with a measured radiative quantum yield of -10 -I to 10-~; the transition appears to be at least partially self-activated (SA) in origin, based on previously reported PL data. Excited-state communication involving the two emissive states is inferred from time-resolved PL measurements. Stable photoelectrochemical cells (PEC's) can be constructed from n-ZnSe:A1 electrodes and aqueous diselenide or ditelluride electrolytes. Applied potential quenches both of the photoanodes' PL bands roughly in parallel. The extent of PL quenching is consistent with a dead-layer model previously used to describe quenching in Au-ZnSe Schottky diodes. When used as a dark cathode in aqueous, alkaline peroxydisulfate electrolyte, EL from ZnSe:A1 electrodes is observed. PL and EL spectral distributions are similar and indicate that the same emissive excited states are populated in the two experiments. Measured EL efficiencies, -10 -4 to 10 -6 at -2.2 and -1.8V vs. SCE, respectively, are much smaller than PL efficiencies. Possible sources of the discrepancies are discussed.Keen interest in photoelectrochemical cells (PEC's) has focused attention on the excited-state properties of the semiconductor electrodes which serve as the key element of these devices (1). We and others have studied photoluminescence (PL) and electroluminescence (EL) from a variety of II-VI and III-V semiconductor electrodes in an effort to determine the effect of PEC parameters on the solids' excited-state deactivation routes (2). In general, measured radiative quantum yields, ~br, of these materials have been small, -10-3-10 -~. We describe in this paper an electrode, n-ZnSe:A1, whose emission competes favorably (~br -10-1-10 -2) with other deactivation paths in stable, efficient PEC's. As observed with other semiconductor electrodes (3), the PL of n-ZnSe:A1 electrodes can be perturbed and EL initiated by interfacial charge-transfer processes. We show that PL quenching by applied potential is compatible with a dead-layer mode] used to describe such quenching in other PEC's (4, 5) and in Au-ZnSe Schottky diodes (6).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19 Downloaded on 2015-06-07 to IP

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Section: Pec Properties--althoughmentioning

confidence: 99%

Zinc Selenide Photoelectrodes: Efficient Radiative Recombination in a Stable Photoelectrochemical Cell

Smiley

Biagioni

Ellis

1984

J. Electrochem. Soc.

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“…20 A second section of the course extends the single-electron theme to a unit on photochemistry. The close relationship between photochemistry and electrochemistry has long been an important topic in inorganic chemistry courses; examples are drawn from both solid-state materials 21 and organometallics. 22 In Reactivity III, the importance of this topic is further emphasized by looking at the atmospheric phenomena of ozone and smog; environmental issues are an excellent vehicle for chemistry content.…”

Section: Overview Of Course Contentmentioning

confidence: 99%

“…A second section of the course extends the single-electron theme to a unit on photochemistry. The close relationship between photochemistry and electrochemistry has long been an important topic in inorganic chemistry courses; examples are drawn from both solid-state materials and organometallics . In Reactivity III, the importance of this topic is further emphasized by looking at the atmospheric phenomena of ozone and smog; environmental issues are an excellent vehicle for chemistry content. , A discussion of some recent studies in photoredox catalysis provides a unifying thread that ties electrochemistry and photochemistry together, and photosynthesis provides a classic example of a similar concept from biochemistry.…”

Section: Chem 315: Reactivity IIImentioning

confidence: 99%

Reactivity III: An Advanced Course in Integrated Organic, Inorganic, and Biochemistry

2017

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Reactivity III is a new course that presents chemical reactions from the domains of organic, inorganic, and biochemistry that are not readily categorized by electrophile–nucleophile interactions. Many of these reactions involve the transfer of a single electron, in either an intermolecular fashion in the case of oxidation/reduction reactions or an intramolecular fashion in the case of photochemical events. Others, such as pericyclic reactions, involve movement of electron pairs but lack obvious acid/base analogies and build on an understanding of photochemistry.

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“…It is noteworthy that the surface, despite its critical role in adduct formation, is poorly characterized under the experimental conditions generally employed for chemical sensing and may contain impurities (oxide phases, traces of water, etc.). The electronic structure of these semiconductors is sketched in Figure 2 (1,6). Salient features are the valence band, comprising largely filled, closely spaced energy levels; and the conduction band, consisting of largely empty, closely spaced energy levels.…”

Section: Physical and Electronic Structurementioning

confidence: 99%

“…The electronic structure of these semiconductors is sketched in Figure 2 (1,6). It is noteworthy that the surface, despite its critical role in adduct formation, is poorly characterized under the experimental conditions generally employed for chemical sensing and may contain impurities (oxide phases, traces of water, etc.).…”

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Modulation of the Photoluminescence of Semiconductors by Surface Adduct Formation: An Application of Inorganic Photochemsitry to Chemical Sensing

et al. 1997

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Semiconductors provide a unique perspective on inorganic photochemistry. The electronic structure of common semiconductors permits a coupling of optical and electrical phenomena (1). As a consequence, semiconductors have found widespread use in many common electrooptical devices, including light-emitting diodes (LEDs), diode lasers, and solar cells. In the case of LEDs and diode lasers, electrical excitation produces a highly emissive excited state of the solid; in contrast, in solar cells, photoexcitation can produce an electrical output.Interfaces derived from semiconducting solids afford opportunities for chemical control of their electro-optical properties. The intent of this article is to describe the construction and operation of chemical sensors based on the photoluminescence (PL) of semiconducting solids. We and others have shown that adduct formation involving the binding of ambient molecules to the semiconductor surface can lead to reversible PL changes that can be used as the basis for on-line sensor structures (2, 3). Because these devices link surface coordination chemistry to the electrical and excited-state properties of the semiconductor substrates, they provide a rich collection of applications of inorganic photochemistry. Physical and Electronic StructureOf the common inorganic semiconductors, the emissive II-VI compounds CdS and CdSe [CdS(e)] have proven to be particularly versatile sensor substrates. These solids have the wurtzite crystal structure, illustrated in Figure 1, which comprises hexagonal closepacked chalcogen atoms with half of the tetrahedral holes filled by cadmium atoms (4). Thus, each type of atom is tetrahedrally coordinated exclusively by atoms of the other type. Figure 1 also reveals the polar nature of the CdS(e) crystal: the (0001) face at the top of the figure consists exclusively of Cd atoms, and the opposing (0001) face exclusively of chalcogen atoms (5). Most studies of adduct formation onto single-crystal CdS(e) samples have employed the more highly emissive (0001) face, which is more accurately described as a Cd-rich

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Excited-state processes of relevance to photoelectrochemistry

Cited by 11 publications

References 17 publications

Zinc Selenide Photoelectrodes: Efficient Radiative Recombination in a Stable Photoelectrochemical Cell

Zinc Selenide Photoelectrodes: Efficient Radiative Recombination in a Stable Photoelectrochemical Cell

Reactivity III: An Advanced Course in Integrated Organic, Inorganic, and Biochemistry

Modulation of the Photoluminescence of Semiconductors by Surface Adduct Formation: An Application of Inorganic Photochemsitry to Chemical Sensing

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