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Exploring the Electronic and Optical Properties of Cu(In,Ga) Se2
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , vii, 63 p.
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-160949ISBN: 978-91-7595-453-0 (print)OAI: oai:DiVA.org:kth-160949DiVA: diva2:792790
Presentation
2015-03-06, Sal N111, Brinellvägen 23, KTH, Stockholm, 11:00 (English)
Opponent
Supervisors
Note

QC 20150305

Available from: 2015-03-05 Created: 2015-03-05 Last updated: 2015-03-09Bibliographically approved
List of papers
1. Parameterization of CuIn1-xGaxSe2 (x=0, 0.5, and 1) energy bands
Open this publication in new window or tab >>Parameterization of CuIn1-xGaxSe2 (x=0, 0.5, and 1) energy bands
2011 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 21, 7503-7507 p.Article in journal (Refereed) Published
Abstract [en]

Parameterization of the electronic band structure of CuIn(1-x)Ga(x)Se(2) (x=0, 0.5, and 1) demonstrates that the energy dispersions of the three uppermost valence bands [E(j)(k); j=v1, v2, and v3] are strongly anisotropic and non-parabolic even very close to the Gamma-point valence-band maximum E,(0). Also the lowest conduction band E(c1) (k) is anisotropic and non-parabolic for energies similar to 0.05 eV above the band-gap energy. Since the electrical conductivity depends directly on the energy dispersion, future electron and hole transport simulations of CuIn(1-x)Ga(x)Se(2) need to go beyond the parabolic approximation of the bands. We therefore present a parameterization of the energy bands, the k-dependency of the effective electron and hole masses m(f)(k), and also an average energy-dependent approximation of the masses m(j)(E).

Keyword
CuInSe(2), CuGaSe(2), Chalcopyrite, Solar cells, Band structure, Electronic structure, Effective mass
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-45289 (URN)10.1016/j.tsf.2010.12.216 (DOI)000295347700088 ()2-s2.0-80052151715 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20111028

Available from: 2011-10-28 Created: 2011-10-28 Last updated: 2017-05-23Bibliographically approved
2. Band-edge density-of-states and carrier concentrations in intrinsic and p-type CuIn1-xGaxSe2
Open this publication in new window or tab >>Band-edge density-of-states and carrier concentrations in intrinsic and p-type CuIn1-xGaxSe2
2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 10, 103708- p.Article in journal (Refereed) Published
Abstract [en]

The electronic structures of chalcopyrite CuIn1-xGaxSe2 have recently been reported to have strongly anisotropic and non-parabolic valence bands (VBs) even close to the Gamma-point VB maximum. Also, the lowest conduction band (CB) is non-parabolic for energies 50-100 meV above the CB minimum. The details in the band-edge dispersion govern the material's electrical properties. In this study, we, therefore, analyze the electronic structure of the three uppermost VBs and the lowest CB in CuIn1-xGaxSe2 (x = 0, 0.5, and 1). The parameterized band dispersions are explored, and the density-of-states (DOS) as well as the constant energy surfaces are calculated and analyzed. The carrier concentration and the Fermi energy E-F in the intrinsic alloys as functions of the temperature is determined from the DOS. The carrier concentration in p-type materials is modeled by assuming the presence of Cu vacancies as the acceptor type defect. We demonstrate that the non-parabolicity of the energy bands strongly affects the total DOS. Therefore, it is important to take into account full band dispersion of the VBs and CB when analyzing the free carrier concentration, like for instance, in studies of electronic transport and/or measurements that involve strong excitation conditions.

Keyword
N-Type, Electronic-Properties, Solar-Cells, Thin-Films, Cuinse2, Cugase2, Transport, Germanium, Crystals, Silicon
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-109640 (URN)10.1063/1.4767120 (DOI)000311969800064 ()2-s2.0-84870697429 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130109

Available from: 2013-01-09 Created: 2013-01-08 Last updated: 2017-05-23Bibliographically approved
3. Dielectric function spectra at 40 K and critical-point energies for CuIn0.7Ga0.3Se2
Open this publication in new window or tab >>Dielectric function spectra at 40 K and critical-point energies for CuIn0.7Ga0.3Se2
Show others...
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 26, 261903- p.Article in journal (Refereed) Published
Abstract [en]

We report ellipsometrically determined dielectric function ε spectra for CuIn0.7Ga0.3Se2 thin film at 40 and 300 K. The data exhibit numerous spectral features associated with interband critical points (CPs) in the spectral range from 0.74 to 6.43 eV. The second-energy-derivatives of ε further reveal a total of twelve above-bandgap CP features, whose energies are obtained accurately by a standard lineshape analysis. The ε spectra determined by ellipsometry show a good agreement with the results of full-potential linearized augmented plane wave calculations. Probable electronic origins of the CP features observed are discussed.

Keyword
Interband Critical-Points, Temperature-Dependence, Spectroscopic Ellipsometry, Thin-Films, Electronic-Structure, Cuin1-Xgaxse2, Cuinse2
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-116662 (URN)10.1063/1.4773362 (DOI)000312830700025 ()2-s2.0-84871730503 (Scopus ID)
Note

QC 20130123

Available from: 2013-01-23 Created: 2013-01-22 Last updated: 2017-05-23Bibliographically approved

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Licentiate Thesis(5415 kB)220 downloads
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