About the band gap nature of FeS2 as determined from optical and photoelectrochemical measurements

Ferrer, Isabel J.; Nevskaia, D.M.; Heras, C. de las; Sánchez, Carlos

doi:10.1016/0038-1098(90)90455-k

Cited by 163 publications

(68 citation statements)

References 18 publications

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“…Two prominent CP features are evident in the SE data at ~2.0 eV and ~4.0 eV, as also observed in early studies. [8][9][10][11][12][13] Although the calculations slightly overestimate the CP energies below 3 eV and underestimate those above it, the overall agreement between experimental and theoretical results is obvious. All six of the major CP features observed experimentally are captured in the DFT calculations.…”

Section: Resultssupporting

confidence: 54%

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Pseudodielectric function and critical-point energies of iron pyrite

Choi

Abdallah

et al. 2012

Phys. Rev. B

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Spectroscopic ellipsometry was used to determine the pseudodielectric function <ε> = <ε 1 > + i<ε 2 > spectrum of a natural single crystal of iron pyrite (cubic FeS 2 ) from 0.5 to 4.5 eV with the sample at 77 K.The <ε> spectrum exhibits several pronounced optical features associated with the interband critical points (CPs). Accurate CP energies are obtained by fitting standard lineshapes to second-energyderivatives of the <ε> data. The electronic origins of the six observed CP features are identified through density functional theory (DFT) calculations and momentum matrix analyses. a) Author to whom correspondence should be addressed. Electronic mail: sukgeun.choi@nrel.gov.2

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Section: Resultssupporting

confidence: 54%

“…5 However, only a limited number of ε and N spectra are available for pyrite from electronic structure calculations [6][7][8][9] or optical reflectance measurements. [10][11][12][13] Moreover, significant discrepancies exist among the reported spectra and no trustworthy theoretical explanation has been made available so far.…”

Section: Introductionmentioning

confidence: 99%

Pseudodielectric function and critical-point energies of iron pyrite

Choi

Abdallah

et al. 2012

Phys. Rev. B

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“…The onset of the absorption at 0.9 eV corresponds to the indirect band gap found in bulk crystals of 0.8-1.2 eV. 28,46 The direct band gap at $2.62 eV 47 is reflected in the extinction spectra by the increasing slope at wavelengths below 500 nm. We do not observe quantum size effects for the nanocrystals reported here.…”

Section: Tunable Optical Properties Of Dispersions and Thin Filmsmentioning

confidence: 99%

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

Döblinger

Vaneski

et al. 2011

J. Mater. Chem.

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Nanocrystals from non-toxic, earth abundant materials have recently received great interest for their potential large-scale application in photovoltaics and photocatalysis. Here, we report for the first time on the shape-controlled and scalable synthesis of phase-pure pyrite (FeS 2 ) nanocrystals employing the simple, inexpensive, thermal reaction of iron-oleylamine complexes with sulfur in oleylamine. Either dendritic nanocrystals (nanodendrites) or nanocubes are obtained by adjusting the iron-oleylamine concentration and thereby controlling the nucleus concentration and kinetics of the nanocrystal growth. Pyrite nanodendrites are reversibly assembled by washing with toluene and redispersed by adding the ligand oleylamine. The assembly-redispersion-process is accompanied by an increased absorption in the red/near-infrared spectral region for the aggregated state. This increased low-energy absorption is due to interactions between the closed-packed nanocrystals. High-concentration nanodendrite dispersions are used to prepare pyrite thin films with strong broadband extinction in the visible and near-infrared. These films are attractive candidates for light harvesting in all inorganic solar cells based on earth abundant, non-toxic materials as well as for photocatalytic applications.

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“…3 Although an indirect gap material, its optical absorption coefficient within the visible light spectrum is on the order of 10 5 cm −1 , 2 outperforming silicon by two orders of magnitude and even direct gap materials such as GaAs. In a recent cost analysis for largescale photovoltaic applications, pyrite is ranked number one among all practical or promising thin-film solar cell materials.…”

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confidence: 99%

First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

2011

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Despite the many advantages (e.g., suitable band gap, exceptional optical absorptivity, earth abundance) of pyrite as a photovoltaic material, its low open circuit voltage (OCV) has remained the biggest challenge preventing its use in practical devices. Two of the most widely-accepted reasons for the cause of the low OCV are: (i) Fermi level pinning due to intrinsic surface states that appear as gap states; (ii) the presence of the metastable polymorph, marcasite. In this paper, we investigate these claims, via density-functional theory (DFT), by examining the electronic structure, bulk, surface, and interfacial energies of pyrite and marcasite. Regardless of whether the Hubbard U correction is applied, the intrinsic {100} surface states are found to be of d z 2 character, as expected from ligand field theory. However, they are not gap states, but located at the conduction band edge. Thus, ligand field splitting at the symmetry-broken surface cannot be the sole cause of the low OCV. We also investigate epitaxial growth of marcasite on pyrite. Based on the surface, interfacial, and strain energies of pyrite and marcasite, we find from our model that only one layer of epitaxial growth of marcasite is thermodynamically favorable. Within all methods used (LDA, GGA-PBE, GGA-PBE+U , GGA-AM05, GGA-AM05+U , HSE06, ∆-sol), the marcasite Kohn-Sham gap is not less than the pyrite Kohn-Sham gap, and is even larger than the experimental marcasite gap. Moreover, gap states are not observed at the pyrite-marcasite interface. We conclude that intrinsic surface states or presence of marcasite is unlikely to undermine the photovoltaic performance of pyrite.

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About the band gap nature of FeS2 as determined from optical and photoelectrochemical measurements

Cited by 163 publications

References 18 publications

Pseudodielectric function and critical-point energies of iron pyrite

Pseudodielectric function and critical-point energies of iron pyrite

Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly

First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

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