Confined and Chemically Flexible Grain Boundaries in Polycrystalline Compound Semiconductors

Grain boundaries (GBs) in polycrystalline Cu(In,Ga)Se2 thin films exhibit only slightly enhanced recombination, as compared with the grain interiors, allowing for very high power‐conversion efficiencies of more than 20% in the corresponding solar‐cell devices. This work highlights the specific compositional and electrical properties of Cu(In,Ga)Se2 GBs by application of appropriate subnanometer characterisation techniques: inline electron holography, electron energy‐loss spectroscopy, and atom‐probe tomography. It is found that changes of composition at the GBs are confined to regions of only about 1 nm in width. Therefore, these compositional changes are not due to secondary phases but atomic or ionic redistribution within the atomic planes close to the GBs. For different GBs in the Cu(In,Ga)Se2 thin film investigated, different atomic or ionic redistributions are also found. This chemical flexibility makes polycrystalline Cu(In,Ga)Se2 thin films particularly suitable for photovoltaic applications.

[1]  Bernhard Schaffer,et al.  Sample preparation for atomic-resolution STEM at low voltages by FIB. , 2012, Ultramicroscopy.

[2]  D. Abou‐Ras,et al.  Direct insight into grain boundary reconstruction in polycrystalline Cu(In,Ga)SE2 with atomic resolution. , 2012, Physical review letters.

[3]  D. Hariskos,et al.  New world record efficiency for Cu(In,Ga)Se2 thin‐film solar cells beyond 20% , 2011 .

[4]  D. Abou‐Ras,et al.  Characterization of Grain Boundaries in Cu(In,Ga)Se$_{\bf 2}$ Films Using Atom-Probe Tomography , 2011, IEEE Journal of Photovoltaics.

[5]  D. Abou‐Ras,et al.  Symmetry-dependence of electronic grain boundary properties in polycrystalline CuInSe2 thin films , 2011 .

[6]  Sidney R. Cohen,et al.  Nanometer-scale electronic and microstructural properties of grain boundaries in Cu(In,Ga)Se2 , 2011 .

[7]  D. Raabe,et al.  Atomic-scale distribution of impurities in CuInSe2-based thin-film solar cells. , 2011, Ultramicroscopy.

[8]  R. Caballero,et al.  Direct evidence for a reduced density of deep level defects at grain boundaries of Cu(In,Ga)Se2 thin films. , 2010, Physical review letters.

[9]  A. Bleloch,et al.  Smart acquisition EELS , 2010 .

[10]  Susanne Siebentritt,et al.  Large neutral barrier at grain boundaries in chalcopyrite thin films. , 2010, Physical review letters.

[11]  R. Würz,et al.  Design of a laser-assisted tomographic atom probe at Münster University. , 2010, The Review of scientific instruments.

[12]  N. Barreau,et al.  Atom probe study of sodium distribution in polycrystalline Cu(In,Ga)Se2 thin film , 2010 .

[13]  R. Scheer,et al.  Influence of grain boundaries on current collection in Cu(In,Ga)Se2 thin-film solar cells , 2009 .

[14]  H. Schock,et al.  Impact of the Ga concentration on the microstructure of CuIn1–x Gax Se2 , 2008 .

[15]  I. Repins,et al.  19·9%‐efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor , 2008 .

[16]  Suhuai Wei,et al.  Electrically benign behavior of grain boundaries in polycrystalline CuInSe2 films. , 2007, Physical review letters.

[17]  Michael K Miller,et al.  Review of Atom Probe FIB-Based Specimen Preparation Methods , 2007, Microscopy and Microanalysis.

[18]  J. Werner,et al.  High quality baseline for high efficiency, Cu(In1−x,Gax)Se2 solar cells , 2007 .

[19]  I. Balberg,et al.  Current routes in polycrystalline CuInSe2 and Cu(In,Ga)Se2 films , 2007 .

[20]  S. Bhattacharyya,et al.  Projected potential profiles across interfaces obtained by reconstructing the exit face wave function from through focal series. , 2006, Ultramicroscopy.

[21]  A. Zunger,et al.  Compositionally induced valence-band offset at the grain boundary of polycrystalline chalcopyrites creates a hole barrier , 2005 .

[22]  Leonard J. Brillson,et al.  Direct observation of copper depletion and potential changes at copper indium gallium diselenide grain boundaries , 2005 .

[23]  D. F. Marrón,et al.  Electrical activity at grain boundaries of Cu ( In , Ga ) Se 2 thin films , 2005 .

[24]  J. Pankow,et al.  Local built-in potential on grain boundary of Cu(In,Ga)Se2 thin films , 2004 .

[25]  A. Zunger,et al.  Anomalous grain boundary physics in polycrystalline CuInSe2: the existence of a hole barrier. , 2003, Physical review letters.

[26]  S. Siebentritt,et al.  Defects and transport in the wide gap chalcopyrite CuGaSe2 , 2003 .

[27]  Dunin-Borkowski.  The development of Fresnel contrast analysis, and the interpretation of mean inner potential profiles at interfaces , 2000, Ultramicroscopy.

[28]  A. Zunger,et al.  Defect physics of the CuInSe 2 chalcopyrite semiconductor , 1998 .

[29]  D. Cahen,et al.  Direct evidence for diffusion and electromigration of Cu in CuInSe2 , 1997 .

[30]  R. Nipoti,et al.  Images of grain boundaries in polycrystalline silicon solar cells by electron and ion beam induced charge collection , 1996 .

[31]  Peter Rez,et al.  Dirac–Fock calculations of X-ray scattering factors and contributions to the mean inner potential for electron scattering , 1994 .

[32]  K. Knight.  The crystal structures of CuInSe2 and CuInTe2 , 1992 .

[33]  D. Dunlavy,et al.  Defect level identification in copper indium selenide (CuInSe2) from photoluminescence studies , 1990 .

[34]  J. Seto.  The electrical properties of polycrystalline silicon films , 1975 .

[35]  S. Abrahams,et al.  Piezoelectric nonlinear optic CuGaSe2 and CdGeAs2: Crystal structure, chalcopyrite microhardness, and sublattice distortion , 1974 .

[36]  C. Koch.  A flux-preserving non-linear inline holography reconstruction algorithm for partially coherent electrons. , 2008, Ultramicroscopy.

[37]  David B. Williams,et al.  Transmission Electron Microscopy: A Textbook for Materials Science , 1996 .

[38]  David B. Williams,et al.  Transmission Electron Microscopy , 1996 .