Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “CATIONS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Electronic absorption spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. II. The phenanthrene cation (C14H10+) and its 1-methyl derivative

The ultraviolet, visible, and near infrared absorption spectra of phenanthrene (C14H10), 1-methylphenanthrene [(CH3)C14H9], and their radical ions [C14H10+; (CH3)C14H9+], formed by vacuum-ultraviolet irradiation, were measured in neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed. The oscillator strengths were calculated for the phenanthrene ion and found lower than the theoretical predictions. This study presents the first spectroscopic data for phenanthrene and its methyl derivative trapped in a neon matrix where the perturbation of the isolated species by its environment is minimum; a condition crucial to astrophysical applications.

NASA Discipline Exobiology↗
DOE OSTI2019

14.1% CsPbI3 Perovskite Quantum Dot Solar Cells via Cesium Cation Passivation

Surface manipulation of quantum dots (QDs) has been extensively reported to be crucial to their performance when applied into optoelectronic devices, especially for photovoltaic devices. In this work, an efficient surface passivation method for emerging CsPbI3 perovskite QDs using a variety of inorganic cesium salts (cesium acetate (CsAc), cesium idodide (CsI), cesium carbonate (Cs2CO3), and cesium nitrate (CsNO3)) is reported. The Cs-salts post-treatment can not only fill the vacancy at the CsPbI3 perovskite surface but also improve electron coupling between CsPbI3 QDs. As a result, the free carrier lifetime, diffusion length, and mobility of QD film are simultaneously improved, which are beneficial for fabricating high-quality conductive QD films for efficient solar cell devices. After optimizing the post-treatment process, the short-circuit current density and fill factor are significantly enhanced, delivering an impressive efficiency of 14.10% for CsPbI3 QD solar cells. In addition, the Cs-salt-treated CsPbI3 QD devices exhibit improved stability against moisture due to the improved surface environment of these QDs. These findings will provide insight into the design of high-performance and low-trap-states perovskite QD films with desirable optoelectronic properties.

14 SOLAR ENERGY↗
DOE OSTI2017

Oxidative Hydrophenylation of Ethylene Using a Cationic Ru(II) Catalyst: Styrene Production with Ethylene as the Oxidant

The complex [(MeOTTM)Ru(P(OCH 2 ) 3 CEt)(NCMe)Ph][BAr' 4 ] (MeOTMM = 4,4',4"-(methoxymethanetriyl)-tris(1-benzyl-1H-1,2,3-triazole), BAr' 4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) is used to catalyze the hydrophenylation of ethylene to produce styrene and ethylbenzene. The selectivity of styrene versus ethylbenzene varies as a function of ethylene pressure, and replacing the MeOTTM ligand with tris(1-phenyl-1H-1,2,3-triazol-4-yl)methanol reduces the selectivity toward styrene. For styrene production ethylene serves as the oxidant to produce ethane, as determined by both 1 H NMR spectroscopy and GC-MS. The Ru(III/II) potentials of [(MeOTTM)Ru[P(OCH 2 ) 3 CEt](NCMe)Ph][BAr' 4 ] (0.86 V) and [(HC(pz 5 ) 3 )Ru[P(OCH 2 ) 3 CEt](NCMe)Ph][BAr' 4 ] (0.82 V) (HC(pz 5 ) 3 = tris(5-methyl-pyrazolyl)methane) are nearly identical. Since catalytic conversion of ethylene and benzene by [(HC(pz 5 ) 3 )Ru[P(OCH 2 ) 3 CEt](NCMe)Ph][BAr' 4] is known to selectively produce ethylbenzene, the formation of styrene using [(MeOTTM)Ru[P(OCH 2 ) 3 CEt](NCMe)Ph][BAr' 4 ] is attributed to the substituents on the triazole rings of the MeOTTM ligand.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Cation ratio fluctuations in Cu 2 ZnSnS 4 at the 20 nm length scale investigated by analytical electron microscopy

Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) is a sustainable material for thin‐film photovoltaics with device efficiencies greater than 12% have been demonstrated. Despite similar crystal structure and polycrystalline film microstructures, there is widespread evidence for larger‐amplitude potential and bandgap fluctuations in CZTS than in the analogous Cu(In,Ga)Se 2 (CIGSe) chalcopyrite material. This disorder is believed to account for a sizable part of the larger open‐circuit voltage ( V OC ) deficit in CZTS devices, yet the detailed origins and length scales of these fluctuations have not been fully elucidated. Herein, we present a transmission electron microscopy study focusing on composition variation within bulk multicrystals of CZTS grown by the travelling heater method (THM). In these slow‐cooled, solution grown crystals we find direct evidence for spatial composition fluctuations of amplitude <1 at.% (∼5 × 10 20 cm −3 ) and thus, explainable by point defects. However, rather than being homogeneously‐distributed we find a characteristic 20 nm length scale for these fluctuations, which sets a definite length scale for band gap and potential fluctuations. At Σ3 grain boundaries, we find no evidence of composition variation compared to the bulk. The finding highlights such variations reported at grain boundaries in polycrystalline thin‐films are direct consequences of processing methods and not intrinsic properties of CZTS itself.

Aguiar, Jeffery A.↗