Abou-Ras, D.

Genzel, C.

Klaus, M.

Marquart, J.

Rissom, T.

Schmid, T.

Schorr, S.

Schulli, T.

Schäfer, N.

Wilkinson, A. J.

N. Schäfer

M. Klaus

C. Genzel

J. Marquart

S. Schorr

T. Rissom

A.J. Wilkinson

T. Schulli

T. Schmid

D. Abou-Ras

Crossref

Microscopy and Microanalysis

Comparison of Techniques for Strain Measurements in CuInSe<sub>2</sub> Absorber Layers of Thin-film Solar Cells

Abou-Ras, Daniel

Institutional Repository of the Freie Universität Berlin

Comparison of Techniques for Strain Measurements in CuInSe2 Absorber Layers of Thin-film Solar Cells  N. Schäfer1, M. Klaus1, C. Genzel1, J. Marquart1,2, S. Schorr1,2, T. Rissom1, A.J. Wilkinson3 , T. Schulli4, T. Schmid5, D. Abou-Ras1  1. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany 2. Freie Universitaet Berlin, Institute of Geological Sciences, Malteserstr. 74-100, 12249 Berlin, Germany 3. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K. 4. European Synchrotron Radiation Facility, BP 220, Grenoble Cedex, France 5. Federal Institute for Materials Research and Testing, Richard-Willstätter-Str. 11, 12205 Berlin, Germany  Chalcopyrite-type solar cells based on Cu(In,Ga)Se2 absorber layers have shown power-conversion efficiencies of more than 20 % on glass and polyimide substrates. The analysis of the microstructure of the Cu(In,Ga)Se2 absorber layer is essential for further improvement of the photovoltaic performance. Cu(In,Ga)Se2 thin films produced by co-evaporation are subject to strain due to recrystallization processes during growth. Since quaternary Cu(In,Ga)Se2 absorber layers exhibit substantial chemical gradients and grain sizes depending on the final chemical composition [1,2], ternary CuInSe2 thin films were used for a comparative study of different techniques for macrostrain and microstrain analyses. A further favorable feature of these thin films is the average grain sizes of more than 1 µm, which is suitable with respect to the spatial resolutions of the techniques applied.  For the investigation of the macrostrain and microstrain in polycrystalline CuInSe2 thin films, electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and Raman spectroscopy measurements were employed. While macroscopic XRD experiments were performed on a five-circle ETA diffractometer, microdiffraction within individual grains was conducted at the ID01 Microdiffraction Imaging beamline at the European Synchrotron Radiation Facility, Grenoble, France. In addition, information on microstrain was extracted by the Williamson-Hall method from XRD data acquired under grazing incidence using a PANalytical X’pert Pro diffractometer. Raman spectra were collected using a Horiba Jobin Yvon LabRam HR spectrometer coupled to an Olympus BX41 microscope. EBSD maps were measured using a Zeiss Ultra Plus scanning electron microscope equipped with a NordlysNano EBSD detector as well as using the Oxford Instruments AZtec acquisition and evaluation software. The recorded EBSD patterns were evaluated by means of the software CrossCourt (BLG Productions). Shifts in EBSD patterns can directly be correlated with strain distributions within individual grains (see Figure 1). Based on a specific reference pattern, strain distributions can be calculated within individual grains with a spatial resolution of about 50 nm [3].  The results on the strain distributions obtained by the different diffraction techniques were compared, also with respect to the relationships between macrostrain and microstrain. It is the aim to correlate the local strain distributions in CuInSe2 thin films to the optoelectronic properties of the corresponding solar cells obtained by means of electron-beam-induced current and cathodoluminescence measurements.  1464doi:10.1017/S1431927614009052Microsc. Microanal. 20 (Suppl 3), 2014© Microscopy Society of America 2014[1] D. Abou-Ras et al., JOM, Vol. 65, No. 9, 2013, p. 1222. [2] D. Abou-Ras et al., Solar Energy Materials & Solar Cells 95 (2011) p. 1452. [3] A.J. Wilkinson et al., Ultramicroscopy 106 (2006) p. 307.               Figure 1: Orientation distribution map of CuInSe2 absorber layer (left). Calculated strain distribution map within individual grain (right).  1465Microsc. Microanal. 20 (Suppl 3), 2014

Comparison of techniques for strain measurements in CuInSe2 absorber layers of
thin-film solar cells

Marquardt, J.

Schulli, C.

Abou Ras, D.

HZB Repository

Comparison of Techniques for Strain Measurements in CuInSe2 Absorber Layers of Thin film Solar Cells

https://refubium.fu-berlin.de/bitstream/fub188/14247/1/S1431927614009052a.pdf

Comparison of techniques for strain measurements in CuInSe2 absorber layers of
thin-film solar cells

Comparison of techniques for strain measurements in CuInSe2 absorber layers of thin-film solar cells

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Institutional Repository of the Freie Universität Berlin

HZB Repository