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Tuesday, August 12 • 08:30 - 10:30
Material Structure II

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8:30-8:45

Oral: Hermann Detz
Atomistic Modeling of Bond Lengths in Ternary III-V Semiconductor Alloy
Co-authors: Gottfried Strasser

8:45-9:00
Oral: Naoki Matsushima
First Principles Study on X-Ray Photoelectron Spectroscopy Binding Energies of Nitrogen in Silicon Carbide
Co-authors: Jun Yamauchi

9:00-9:30
Invited: Yanfa Yan
Physics of Grain Boundaries in Polycrystalline Photovoltaic Semiconductors

Thin-film solar cells based on polycrystalline Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that the efficiencies of these polycrystalline solar cells can reach so high even these thin-films contain grain boundaries (GBs), which are considered to be nonradiative recombination centers for carriers. In the past decade, we have studied the physics of GBs in polycrystalline photovoltaic semiconductors including Si, CdTe, CuInSe2 (CIS), and Cu2ZnSnS4 (CZTS) using a combination of state-of-the-art density-functional theory (DFT) and advanced high-resolution electron microscopy. We have revealed that intrinsic GBs in CIS produce gap states, which act as nonradiative recombination centers. However, the segregation of CuIn and OSe at GBs can clean the gap states and lead to electrically benign GB behavior. Our results suggest that the defect segregation at GBs could be an important feature for high efficiency CIS-based photovoltaic solar cells and it provides a general guidance for engineering GBs in other chalcogenide polycrystalline, such as CZTS. In CdTe, electron microscopy shows that up to 20% Cl has doped into Te sites within a narrow range (1-2 nm) at the GBs. DFT calculations reveal that GB-localized high concentration Cl doping might invert the GBs to n-type, create p-n junctions along the GBs, therefore separate electron-hole carriers at GBs, and improve the cell efficiency.

9:30-9:45
Oral: Pavel Aseev
High In Content InGaN Layers on Si(111) for Near Infrared Applications
Co-authors: Paul Soto, Prveen Kumar, Victor Gomez, Naveed Alvi, Richard Notzel, Zarko Gacevic, Enrique Calleja

9:45-10:00
Oral: Patrick Sims

A New Class of III-V/Group-IV Semiconductor Alloys Based on Molecular Building Blocks with Bulk Crystal Stoichiometry
Co-authors: Liying Jiang, Toshiro Aoki, Andrew Chizmeshya, John Kouvetakis, Jose Menendez, Patrick Sims

10:00-10:15
Open

10:15-10:30
Oral: Yong-Hyun Kim
Detecting Defects with Thermoelectricity at the Atomic Scale
Co-authors: Eui-Sup Lee, Sanghee Cho, Ho-Ki Lyeo 


Session Chairs
JS

Jurgen Smet

Max Planck Institute for Solid State Research
Jurgen Smet is heading the independent research group Solid State Nanophysics at the Max Planck Institute for Solid State Research. He graduated with a Master degree in Electrical Engineering from the Catholic University of Leuven in 1990. In 1994, he received his Ph. D. in Electrical Engineering and Computer Science from the Massachussets Institute of Technology, Cambridge U.S.A, with research on intrawell and interwell intersubband... Read More →

Speakers
YY

Yanfa Yan

ORSP Endowed Chair, The University of Toledo
Dr. Yan’s Research Group is interested in understanding defect physics in inorganic solar cell materials using the combination of density-functional theory, materials synthesis, and electron microscopy characterization. His group is currently involved in exploring the viability of earth-abundant thin-film solar cells. Prof. Yan’s group is also interested in materials discovery and engineering for H2 production through solar water... Read More →


Tuesday August 12, 2014 08:30 - 10:30
Room 17B

Attendees (8)