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Point defect segregation and its role in the detrimental nature of Frank partials in Cu(In,Ga)Se_2 thin-film absorbers

Simsek Sanli, E. and Barragan-Yani, D. and Ramasse, Q. M. and Albe, K. and Mainz, R. and Abou-Ras, D. and Weber, A. and Kleebe, Hans-Joachim and van Aken, Peter A. (2017):
Point defect segregation and its role in the detrimental nature of Frank partials in Cu(In,Ga)Se_2 thin-film absorbers.
In: Physical Review B, pp. 195209 (6), 95, (19), ISSN 2469-9950, [Online-Edition: http://doi.org/10.1103/PhysRevB.95.195209],
[Article]

Abstract

The interaction of point defects with extrinsic Frank loops in the photovoltaic absorber material Cu(In,Ga)Se_2 was studied by aberration-corrected scanning transmission electron microscopy in combination with electron energy-loss spectroscopy and calculations based on density-functional theory. We find that Cu accumulation occurs outside of the dislocation cores bounding the stacking fault due to strain-induced preferential formation of Cu^−2_In , which can be considered a harmful hole trap in Cu(In,Ga)Se_2. In the core region of the cation-containing α-core, Cu is found in excess. The calculations reveal that this is because Cu on In-sites is lowering the energy of this dislocation core. Within the Se-containing β-core, in contrast, only a small excess of Cu is observed, which is explained by the fact that Cu_In and Cu_i are the preferred defects inside this core, but their formation energies are positive. The decoration of both cores induces deep defect states, which enhance nonradiative recombination. Thus, the annihilation of Frank loops during the Cu(In,Ga)Se_2 growth is essential in order to obtain absorbers with high conversion efficiencies.

Item Type: Article
Erschienen: 2017
Creators: Simsek Sanli, E. and Barragan-Yani, D. and Ramasse, Q. M. and Albe, K. and Mainz, R. and Abou-Ras, D. and Weber, A. and Kleebe, Hans-Joachim and van Aken, Peter A.
Title: Point defect segregation and its role in the detrimental nature of Frank partials in Cu(In,Ga)Se_2 thin-film absorbers
Language: English
Abstract:

The interaction of point defects with extrinsic Frank loops in the photovoltaic absorber material Cu(In,Ga)Se_2 was studied by aberration-corrected scanning transmission electron microscopy in combination with electron energy-loss spectroscopy and calculations based on density-functional theory. We find that Cu accumulation occurs outside of the dislocation cores bounding the stacking fault due to strain-induced preferential formation of Cu^−2_In , which can be considered a harmful hole trap in Cu(In,Ga)Se_2. In the core region of the cation-containing α-core, Cu is found in excess. The calculations reveal that this is because Cu on In-sites is lowering the energy of this dislocation core. Within the Se-containing β-core, in contrast, only a small excess of Cu is observed, which is explained by the fact that Cu_In and Cu_i are the preferred defects inside this core, but their formation energies are positive. The decoration of both cores induces deep defect states, which enhance nonradiative recombination. Thus, the annihilation of Frank loops during the Cu(In,Ga)Se_2 growth is essential in order to obtain absorbers with high conversion efficiencies.

Journal or Publication Title: Physical Review B
Volume: 95
Number: 19
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Zentrale Einrichtungen
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ)
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
Date Deposited: 09 Jun 2017 09:18
Official URL: http://doi.org/10.1103/PhysRevB.95.195209
Identification Number: doi:10.1103/PhysRevB.95.195209
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