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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Schottky barrier height measurements of Cu/Si(001), Ag/Si(001), and Au/Si(001) interfaces utilizing ballistic electron emission microscopy and ballistic hole emission microscopy

The Schottky barrier heights of both n and p doped Cu/Si(001), Ag/Si(001), and Au/Si(001) diodes were measured using ballistic electron emission microscopy and ballistic hole emission microscopy (BHEM), respectively. Measurements using both forward and reverse ballistic electron emission microscopy (BEEM) and (BHEM) injection conditions were performed. The Schottky barrier heights were found by fitting to a linearization of the power law form of the Bell-Kaiser BEEM model. The sum of the n-type and p-type barrier heights are in good agreement with the band gap of silicon and independent of the metal utilized. The Schottky barrier heights are found to be below the region of best fit for the power law form of the BK model, demonstrating its region of validity.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Critical Interface: Poly-Silicon to Tunneling SiO2 for Passivated Contact Performance

Environmental exposure of our thin tunneling SiO2 layer on nCz wafer samples prior to poly-Silicon (poly-Si) deposition critically impacts the resulting contact passivation. We present ToF-SIMS evidence of SiO2 oxide storage-induced degradation, presumably by surface contaminants such as carbon, in symmetric and device poly-Si/SiO2 lifetime samples as well as in finished cells. We also present methods to resurrect a contaminated SiO2 layer, including UV-O3 treatment prior to passivated contact formation to produce >21% TCO-free solar cells.

14 SOLAR ENERGY↗
DOE OSTI2014

Interfaces of dicationic ionic liquids and graphene: a molecular dynamics simulation study

Molecular dynamics simulations were performed to investigate the interfacial structure and capacitance of electrical double layers (EDLs) in dicationic ionic liquids (DILs) 1-alkyl-3-dimethylimidazolium tetrafluoroborate [Cn(mim)2](BF4)2 (n = 3, 6, 9), with respect to a baseline of a monocationic ionic liquid [C3mim][BF4], near planar carbon electrodes consisting of graphene sheets. The simulation results show that an adsorbed layer with double peaks is exclusively found for [C3(mim)2](BF4)2, while a single peak of the other three cations is observed at the neutral electrode, due to the difference in ion–wall interaction and cation–anion association. As the electrode becomes negatively charged, the second peak of [C3(mim)2]2+ is dramatically reduced, whereas those of [C6(mim)2]2+ and [C9(mim)2]2+ become non-trivial. The capacitance–potential curve of EDLs in DILs manifests a transition from camel shape to bell shape as the cation chain length increases, which is attributed to the enlargement of ion adsorption (per unit charge) on the electrode and the decrease of attractive interaction between ions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Nonthermal Site Occupation at the Donor-Acceptor Interface of Organic Solar Cells

Here, we investigate the nature of occupation and relaxation within the charge transfer density of states (CT DOS) for bulk heterojunction organic solar cells consisting of the donor boron subphthalocyanine chloride and the acceptor C 60 . We observe relaxation of geminate CT states on a sub-ns timescale via an approximately 70-meV dynamic redshift in their photoluminescence, whereas free carrier relaxation at longer times leads to the formation of nongeminate CT states at even lower energy. In steady state, we find that thermalization within the DOS is incomplete, resulting in a Boltzmann-like CT state distribution characterized by an effective temperature above that of the ambient. These findings confirm that electron and hole populations can be far from equilibrium in organic solar cells and may prompt a reassessment of analyses that assume the same temperature for their charge-carrier distributions in the dark and under illumination.

14 SOLAR ENERGY↗