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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