Why do we make Cu(In,Ga)Se2 solar cells non-stoichiometric?

Siebentritt, Susanne; Gütay, Levent; Regesch, David; Aida, Yasuhiro; Deprédurand, Valérie

doi:10.1016/j.solmat.2013.04.014

Cited by 127 publications

(168 citation statements)

References 69 publications

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“…Urbach energies measured by PL are reported in Table I for a series of CuðIn; GaÞSe 2 thin films with different compositions. Cu-poor samples show larger Urbach energies since the Cu deficiency leads to heavy doping and heavy compensation, which results in band-edge fluctuation and tailing, as observed previously [28]. CIGS shows higher Urbach energies than CIS (with comparable Cu content) because of alloy disorder.…”

Section: A Single Transition Processsupporting

confidence: 68%

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

et al. 2018

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The photoluminescence (PL) of semiconductors can be used to determine their absorption coefficient (α) using Planck's generalized law. The standard method, suitable only for self-supported thick samples, like wafers, is extended to multilayer thin films by means of the transfer-matrix method to include the effect of the substrate and optional front layers. α values measured on various thin-film solar-cell absorbers by both PL and photothermal deflection spectroscopy (PDS) show good agreement. PL measurements are extremely sensitive to the semiconductor absorption and allow us to advantageously circumvent parasitic absorption from the substrate; thus, α can be accurately determined down to very low values, allowing us to investigate deep band tails with a higher dynamic range than in any other method, including spectrophotometry and PDS.

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Section: A Single Transition Processsupporting

confidence: 68%

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

et al. 2018

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“…Finally, our calculations lead to the conclusion that Cu In/Ga is the principal acceptor, with the lowest formation energy in CIS and CGS grown under In-and Ga-poor conditions. This explains why the hole concentration in experiment is found to be higher in samples with an In-and Ga-poor stoichiometry 6,7 .…”

Section: Discussionmentioning

confidence: 89%

“…Supercells of this size can currently hardly be used in DFT, especially in combination with the computationally demanding hybrid functionals. Another important consequence of our first-principles calculations is that under In-poor conditions, the antisite defects Cu In and Cu Ga have the lowest formation energy (form most eas- 6 . This is detrimental to the device performance because it enhances recombination near the interface.…”

Section: Resultsmentioning

confidence: 98%

Native point defects in CuIn_1−xGa_xSe₂: hybrid density functional calculations predict the origin of p- and n-type conductivity

Bekaert

Saniz

Partoens

et al. 2014

Phys. Chem. Chem. Phys.

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“…On the other hand, high-quality solar-cell absorber material is often Cu-poor. [35] Moreover, a larger Cu deficiency is observed at grain surfaces, where the material can start forming so-called ordered defect compounds (ODCs). Point E is taken to model such conditions.…”

Section: Point Defectsmentioning

confidence: 99%

First‐Principles Modeling of Point Defects and Complexes in Thin‐Film Solar‐Cell Absorber CuInSe₂

Malitckaya

Komsa

Havu

et al. 2017

Adv Elect Materials

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as the composition of the sample changes from Cu-rich to Cu-poor, so that in the Cupoor samples only one peak is detected. Although only the Cu-poor material is important for actual devices Cu-rich samples give indispensable information for defect identification.First-principles calculations based on the density functional theory (DFT) can be used to obtain important, complementary information about point defects such as formation energies and charge transition levels. [6] A plethora of studies concerning defects in CuInSe 2 and CuGaSe 2 has been published over the last two decades. [7][8][9][10][11][12][13] The most recent DFT investigations have employed hybrid functionals, which can overcome the energy band gap problem plaguing the older studies and can thus also provide information about the defect level positions within the band gap. [9][10][11][12][13] The results of different calculations agree well with respect to general trends in formation energies of the most important defects, such as the copper vacancy (V Cu ), indium antisite on copper place (In Cu ), and copper interstitial (Cu int ). However, the results differ in some important cases. For instance, there are clearly different values for the ionization levels within the band gap for the copper antisite on the indium place (Cu In ) and indium vacancy (V In ). Based on the formation energy calculations, V Cu and Cu In are abundant acceptors, and are most probably responsible for some of the above-mentioned PL peaks, but it is unclear whether any native defect can be responsible for the third acceptor level.One important goal of the present work was to gain a perspective on the present unsatisfactory situation in modeling point defects in CIGSe and to approach the ultimate accuracy by which DFT is able to predict the properties of bulk crystalline materials. [14] First we carried out a detailed benchmarking of the first-principles computational scheme used. We checked effects due to the supercell size and shape, as well as those of the finite-size supercell correction scheme. We used also two very different implementations of the first-principles DFT method, which differ in describing valence-core electron interaction and electron wave functions (see below). After finding the computational parameters yielding accurate results, we calculated formation energies and charge transition levels for different acceptor candidates in CuInSe 2 . By carefully considering the relevant chemical potential limits, we were able to draw conclusions about the abundances of different defects. In addition to simple native defects, we have also considered a set of complexes formed by them. Our paper is organized as follows.

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Why do we make Cu(In,Ga)Se2 solar cells non-stoichiometric?

Cited by 127 publications

References 69 publications

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

Native point defects in CuIn_1−xGa_xSe₂: hybrid density functional calculations predict the origin of p- and n-type conductivity

First‐Principles Modeling of Point Defects and Complexes in Thin‐Film Solar‐Cell Absorber CuInSe₂

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Why do we make Cu(In,Ga)Se2 solar cells non-stoichiometric?

Cited by 127 publications

References 69 publications

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

Native point defects in CuIn1−xGaxSe2: hybrid density functional calculations predict the origin of p- and n-type conductivity

First‐Principles Modeling of Point Defects and Complexes in Thin‐Film Solar‐Cell Absorber CuInSe2

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Native point defects in CuIn_1−xGa_xSe₂: hybrid density functional calculations predict the origin of p- and n-type conductivity

First‐Principles Modeling of Point Defects and Complexes in Thin‐Film Solar‐Cell Absorber CuInSe₂