From atomic structure to photovoltaic properties in CdTe solar cells

Abstract Aberration corrected scanning transmission electron microscopy (STEM) has been used to determine the structures of a variety of dislocation cores in CdTe, including 30° and 90° Shockley partial dislocations, positive and negative Frank sessile partial dislocations, and steps on twin boundaries. Structure models have been constructed from the images and electrical activity has been investigated with density functional calculations. An integrated electron energy loss spectroscopy, cathodoluminescence and electron beam induced current system has been designed and built to probe electrical and optical properties of individual defects. The first STEM-cathodoluminescence result shows strong impurity segregation between the CdTe and the glass. The correlation between the scanning electron microscopy-electron beam induced current and electron backscatter diffraction maps proves that the grain structures and boundaries dominate the electrical activity. After heat treatment in CdCl2, Cl is found to segregate to the grain boundaries, and they show higher efficiency than the bulk material.

[1]  P. Nellist,et al.  A Bloch wave analysis of optical sectioning in aberration-corrected STEM. , 2007, Ultramicroscopy.

[2]  Ş. Oktik,et al.  Transmission electron microscopy of CdTeCdS based solar cells , 1996 .

[3]  H. Usui,et al.  Growth process and nanostructure of crystalline GaAs on Si(1 1 0) surface prepared by molecular beam epitaxy , 2006 .

[4]  D. Leonard,et al.  Core Structures of Dislocations within CdTe Grains , 2013 .

[5]  F. Louchet,et al.  Dislocation cores in semiconductors. From the « shuffle or glide » dispute to the « glide and shuffle » partnership , 1987 .

[6]  C. Barry Carter,et al.  60° dislocations in (001) GaAs/Si interfaces , 1990 .

[7]  D Van Dyck,et al.  The S-state model: a work horse for HRTEM. , 2002, Ultramicroscopy.

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

[9]  D. Dyck,et al.  Wave function reconstruction in HRTEM: the parabola method , 1996 .

[10]  Martin A. Green,et al.  Solar cell efficiency tables (version 41) , 2013 .

[11]  S. Takeuchi,et al.  Stacking-fault energy of II–VI compounds , 1985 .

[12]  Stephen J. Pennycook,et al.  High-resolution Z-contrast imaging of crystals , 1991 .

[13]  V. Anisimov,et al.  Band theory and Mott insulators: Hubbard U instead of Stoner I. , 1991, Physical review. B, Condensed matter.

[14]  J. F. Nicholas,et al.  CXXVIII. Stable dislocations in the common crystal lattices , 1953 .

[15]  S. Marklund.  Electron states associated with the core region of the 60° dislocation in silicon and germanium , 1978 .

[16]  S. Pennycook,et al.  Depth sectioning with the aberration-corrected scanning transmission electron microscope. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[17]  H. Queisser,et al.  Detailed Balance Limit of Efficiency of p‐n Junction Solar Cells , 1961 .

[18]  G. Kresse,et al.  Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set , 1996 .

[19]  S. Pennycook,et al.  Spectroscopic imaging in electron microscopy , 2012 .

[20]  Martin A. Green,et al.  Solar cell efficiency tables (version 40) , 2012 .

[21]  S. Pennycook,et al.  Depth sectioning of aligned crystals with the aberration-corrected scanning transmission electron microscope , 2006 .

[22]  Yu. G. Sidorov,et al.  Nature of V-shaped defects in HgCdTe epilayers grown by molecular beam epitaxy , 2005 .

[23]  D. B. Holt,et al.  Properties and structure of antiphase boundaries in GaAs/Ge solar cells , 1996 .

[24]  Gengfeng Zheng,et al.  Dislocation-driven CdS and CdSe nanowire growth. , 2012, ACS nano.

[25]  Sidney R. Cohen,et al.  Direct evidence for grain-boundary depletion in polycrystalline CdTe from nanoscale-resolved measurements , 2003 .

[26]  A. Renault,et al.  Core structure of the Lomer dislocation in germanium and silicon , 1982 .

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

[28]  L. Allen,et al.  Three-dimensional ADF imaging of individual atoms by through-focal series scanning transmission electron microscopy. , 2006, Ultramicroscopy.

[29]  O. Krivanek,et al.  CHAPTER 3 – Advances in Aberration-Corrected Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy , 2008 .

[30]  K. Nakagawa,et al.  In situ TEM observation of dislocation motion in II–VI compounds , 1984 .

[31]  P. Nellist,et al.  Towards sub-0.5 A electron beams. , 2003, Ultramicroscopy.

[32]  J. I. Marin-Hurtado,et al.  Temperature dependence of the band gap energy of crystalline CdTe , 2000 .

[33]  Ondrej L. Krivanek,et al.  Towards sub-Å electron beams , 1999 .

[34]  D. Dyck,et al.  The S‐State Model for Electron Channeling in High‐Resolution Electron Microscopy , 2005 .

[35]  D. Cahen,et al.  How Polycrystalline Devices Can Outperform Single‐Crystal Ones: Thin Film CdTe/CdS Solar Cells , 2004 .

[36]  Liuyang Fang,et al.  Microstructural characterization of Cu-poor Cu (In, Ga)Se2 surface layer , 2012 .

[37]  David J. Smith,et al.  Dissociated 60° dislocations in CdTe studied by high-resolution electron microscopy , 1990 .

[38]  C. Humphreys,et al.  Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study , 1998 .

[39]  K. Hiraga,et al.  Dislocations in silicon observed by high-voltage, high-resolution electron microscopy , 1982 .

[40]  P. Pirouz,et al.  Preliminary studies of crystal defects in cadmium sulphide by high-resolution transmission electron microscopy , 1982 .

[41]  P. Specht,et al.  Constricted dislocations and their use for TEM measurements of the velocities of edge and 60° dislocations in silicon. A new approach to the problem of kink migration , 1993 .

[42]  Leslie J. Allen,et al.  Three-dimensional imaging of individual hafnium atoms inside a semiconductor device , 2005 .

[43]  Pennycook,et al.  High-resolution incoherent imaging of crystals. , 1990, Physical review letters.

[44]  Yanfa Yan,et al.  Characterization of extended defects in polycrystalline CdTe thin films grown by close-spaced sublimation , 2001 .

[45]  R. Loo,et al.  High quality, relaxed SiGe epitaxial layers for solar cell application , 1999 .

[46]  Ş. Oktik,et al.  Transmission electron microscopy of CdTe/CdS based solar cells , 1996 .

[47]  D. Van Dyck,et al.  A simple theory for dynamical electron diffraction in crystals , 1999 .

[48]  Blöchl,et al.  Projector augmented-wave method. , 1994, Physical review. B, Condensed matter.

[49]  Jens Lothe John Price Hirth,et al.  Theory of Dislocations , 1968 .

[50]  D. Hull,et al.  Introduction to Dislocations , 1968 .

[51]  D. B. Holt.  Defects in the sphalerite structure , 1962 .

[52]  J. Zaanen,et al.  Density-functional theory and strong interactions: Orbital ordering in Mott-Hubbard insulators. , 1995, Physical review. B, Condensed matter.

[53]  R. Birkmire,et al.  Recrystallization and sulfur diffusion in CdCl2‐treated CdTe/CdS thin films , 1997 .

[54]  K. Durose,et al.  Investigation of post deposition CdCl2 treatment for fully sputtered CdTe/CdS thin film solar cells , 2012, 2012 38th IEEE Photovoltaic Specialists Conference.

[55]  O. L. Krivanek,et al.  Sub-ångstrom resolution using aberration corrected electron optics , 2002, Nature.

[56]  A. George,et al.  Velocities of Screw and 60° Dislocations in n- and p-Type Silicon , 1979, June 16.

[57]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[58]  Jian Yu Huang,et al.  In situ TEM electrochemistry of anode materials in lithium ion batteries , 2011 .

[59]  R. W. Balluffi,et al.  Interfaces in crystalline materials , 2009 .

[60]  S. Beckman,et al.  Dislocation cores and their electronic states: partial dislocations in GaAs , 2003 .

[61]  David Cahen,et al.  Understanding the Beneficial Role of Grain Boundaries in Polycrystalline Solar Cells from Single‐Grain‐Boundary Scanning Probe Microscopy , 2006 .

[62]  K. Hellwege,et al.  Landolt-Börnstein, Numerical Data and Functional Relationships in Science and Technology , 1967 .

[63]  Sidney R. Cohen,et al.  Electronically active layers and interfaces in polycrystalline devices: Cross-section mapping of CdS/CdTe solar cells , 2003 .

[64]  David J. Smith,et al.  A systematic analysis of HREM imaging of Wurtzite semiconductors , 1989 .

[65]  Martin A. Green,et al.  Radiative efficiency of state‐of‐the‐art photovoltaic cells , 2012 .

[66]  W. Schröter,et al.  Velocities of Screw and 60°-Dislocations in Silicon , 1972 .

[67]  P D Nellist,et al.  Direct Sub-Angstrom Imaging of a Crystal Lattice , 2004, Science.

[68]  P. Nellist,et al.  HAADF-STEM imaging with sub-angstrom probes: a full Bloch wave analysis. , 2004, Journal of electron microscopy.

[69]  J. Hornstra.  Dislocations in the diamond lattice , 1958 .

[70]  S Bals,et al.  Quantitative atomic resolution mapping using high-angle annular dark field scanning transmission electron microscopy. , 2009, Ultramicroscopy.