Ellipsometric spectroscopy on polycrystalline CuIn1–xGaxSe2: Identification of optical transitions

Moussa, G. W. El Haj; Ajaka, M.; Tahchi, M. El; Eid, E. A.; Llinarès, C.

doi:10.1002/pssa.200406934

Cited by 19 publications

(8 citation statements)

References 14 publications

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“…The same effects were noticed on the spectra of Cu(In 1−x Ga x ) 3 Se 5 compounds [21]. Cu(In 1−x Ga x ) 3 Se 5 compounds are like CuIn 1−x Ga x Se 2 compounds.…”

Section: Characterization By Photoconductivitysupporting

confidence: 72%

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In1–xGax)3Se5 Bulk Compounds: Identification of Optical Transitions

Habib¹,

Moussa²

2017

WJCMP

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Using Spectroscopic Ellipsometry (SE), the optical properties of Cu(In 1−x Ga x ) 3 Se 5 bulk compounds, grown by the Bridgman method, were analyzed by varying x composition (0 ≤ x ≤ 1). Energy levels above the gap in the band scheme were determined by measuring the complex dielectric function ( ) ( ) ( ) r i i ε ω ε ω ε ω = + at room-temperature for energies between 1.5 and 5.5 eV using a variable angle of incidence ellipsometer. The transitions values E 1 , E 2 and E 3 were observed above the gap for different samples of Cu(In 1−x Ga x ) 3 Se 5 alloy. When a gallium atom replaces an indium atom, one assumes globally that the levels related to selenium and copper are unchanged. Conversely, the levels corresponding to the conduction band are shifted towards higher energies. Thus, the gap increases as the composition of gallium increases. Spectroscopic Ellipsometry (SE) gave evidence for the interpretation of the choice of gap values which were compatible with that obtained from solar spectrum. Several other characterization methods like Energy Dispersive Spectrometry (EDS), hot point probe method, X-ray diffraction, Photoluminescence (PL), Optical response (Photoconductivity) were presented in this paper. The Cu(In 1−x Ga x ) 3 Se 5 have an Ordered Vacancy Chalcopyrite-type structure with lattice constants varying as a function of the x composition. The band gap energy of Cu(In 1−x Ga x ) 3 Se 5 compounds is found to vary from 1.23 eV to 1.85 eV as a function of x.

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“…The same effects were noticed on the spectra of Cu(In 1−x Ga x ) 3 Se 5 compounds [21]. Cu(In 1−x Ga x ) 3 Se 5 compounds are like CuIn 1−x Ga x Se 2 compounds.…”

Section: Characterization By Photoconductivitysupporting

confidence: 72%

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In1–xGax)3Se5 Bulk Compounds: Identification of Optical Transitions

Habib¹,

Moussa²

2017

WJCMP

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“…4b). These E g values agreed satisfactorily with experimental results from other research groups for CIGS films with a similar chemical composition [13,14]. Because the Mo contact layer was opaque so that the transmittance of the CdS/CIGS/Mo/glass structures could not be measured, the band-gap width E g was determined by measuring photoluminescence excitation (PLE) spectra.…”

supporting

confidence: 54%

Structural and optical properties of CdS/Cu(In,Ga)Se2 heterostructures irradiated by high-energy electrons*

et al. 2010

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Thin films of Cu(In, Ga)Se 2 (CIGS) with a Ga/(Ga + In) ratio of ~0.27 corresponding to the standard elemental composition for solar-energy transducers were grown on Mo-coated glass substrates by the Cu, In, Ga, and Se co-evaporation technique from different sources. Transmission (T), photoluminescence (PL), and photoluminescence excitation (PLE) spectra at 4.2 K were used to analyze electronic properties in the asgrown and electron-irradiated CIGS films. The band-gap energy (E g ) of the CIGS films measured using both transmission and PLE methods was found to be about 1.28 eV at 4.2 K. Two deep bands in the PL spectra of the irradiated CIGS films, P 1 at ~0.91 eV and P 2 at ~0.77 eV, have been detected. These bands are tentatively associated with copper atoms substituting indium (Cu In ) and indium vacancies V In , respectively, as the simplest radiation-induced defects.Introduction. Fabrication of highly efficient solar cells based on Cu(In,Ga)Se 2 (CIGS) semiconducting films is a critical and simultaneously complicated scientific and technical problem of modern semiconducting solar energy [1,2]. The development and improvement of the technology for preparing solar cells using CIGS compounds with the chalcopyrite structure has recently enabled efficiency records (~19.9%) to be set for all known thin-film semiconducting materials [1]. The stable operation of solar cells based on CIGS compounds that are used under ordinary terrestrial conditions and, especially, that are exposed to penetrating radiation (high-energy electrons, protons, etc.) in near-earth space orbits to an even greater extent stimulate further scientific and technological developments of semiconducting solar photovoltaics based on these materials [1][2][3][4][5]. Such promising developments prompt investigations that determine the criteria for radiation resistance of CIGS semiconducting compounds and solar cells based on them to the action of high-energy particles and that establish the nature of the radiation-induced defects at the atomic level [3][4][5][6]. New knowledge about the radiation physics of defects in CIGS material will indubitably assist a deeper understanding of the geometric and electronic structure of not only radiation defects but also growth defects formed during formation of CIGS thin films that determine the perfection of the material crystal structure. Herein we describe experiments that establish the nature of the radiation defects in CdS/Cu(In,Ga)Se 2 /Mo (CdS/CIGS/Mo) heterostructures, on which solar cells with efficiency ~12-14% are based [4,7,8].Experimental. The studied CIGS films were sputtered onto glass substrates coated with a thin film of Mo with simultaneous co-evaporation of Cu, In, Ga,[7][8][9]. Layers of CdS (~50 nm thick) were deposited by the standard chemical method in the corresponding solutions. The studied CdS/CIGS/Mo/glass structures consisted of a CdS buffer layer (~50 nm), CIGS films (~1.5 μm thick), a contact layer of Mo (~0.8 μm thick), and the glass substrate (2 mm thick). The elemental compositio...

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“…should be noted that our deflection coefficient b ≈ 0.13 eV at 4.2 K is the lowest of the known values for films and monocrystals of CIGS; this indicates growth of relatively high quality films in which the effects of a chaotic distribution of the components of the compound shows up no more strongly than in the earlier papers [20][21][22][23].…”

Section: Introductionmentioning

confidence: 83%

Structural and optical properties of thin films of Cu(In,Ga)Se2 semiconductor compounds

et al. 2010

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The chemical composition of Cu(In,Ga)Se 2 (CIGS) semiconductor compounds is analyzed by local x-ray spectral microanalysis and scanning Auger electron spectroscopy. X-ray diffraction analysis reveals a difference in the predominant orientation of CIGS films depending on the technological conditions under which they are grown. The chemical composition is found to have a strong effect on the shift in the self-absorption edge of CIGS compounds. It is shown that a change in the relative proportion of Ga and In in CIGS semiconducting compounds leads to a change in the band gap E g for this material in the 1.05-1.72 eV spectral range at 4.2 K.

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Ellipsometric spectroscopy on polycrystalline CuIn_1–xGa_xSe₂: Identification of optical transitions

Cited by 19 publications

References 14 publications

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In<sub>1–x</sub>Ga<sub>x</sub>)<sub>3</sub>Se<sub>5</sub> Bulk Compounds: Identification of Optical Transitions

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In<sub>1–x</sub>Ga<sub>x</sub>)<sub>3</sub>Se<sub>5</sub> Bulk Compounds: Identification of Optical Transitions

Structural and optical properties of CdS/Cu(In,Ga)Se2 heterostructures irradiated by high-energy electrons*

Structural and optical properties of thin films of Cu(In,Ga)Se2 semiconductor compounds

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Ellipsometric spectroscopy on polycrystalline CuIn1–xGaxSe2: Identification of optical transitions

Cited by 19 publications

References 14 publications

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In&lt;sub&gt;1–x&lt;/sub&gt;Ga&lt;sub&gt;x&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;Se&lt;sub&gt;5&lt;/sub&gt; Bulk Compounds: Identification of Optical Transitions

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In&lt;sub&gt;1–x&lt;/sub&gt;Ga&lt;sub&gt;x&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;Se&lt;sub&gt;5&lt;/sub&gt; Bulk Compounds: Identification of Optical Transitions

Structural and optical properties of CdS/Cu(In,Ga)Se2 heterostructures irradiated by high-energy electrons*

Structural and optical properties of thin films of Cu(In,Ga)Se2 semiconductor compounds

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Ellipsometric spectroscopy on polycrystalline CuIn_1–xGa_xSe₂: Identification of optical transitions

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In<sub>1–x</sub>Ga<sub>x</sub>)<sub>3</sub>Se<sub>5</sub> Bulk Compounds: Identification of Optical Transitions

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In<sub>1–x</sub>Ga<sub>x</sub>)<sub>3</sub>Se<sub>5</sub> Bulk Compounds: Identification of Optical Transitions