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361.
21.0%‐efficient co‐diffused screen printed n‐type silicon solar cell with rear‐side boron emitter
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Nadine Wehmeier Bianca Lim Anja Nowack Jan Schmidt Thorsten Dullweber Rolf Brendel 《固体物理学:研究快报》2016,10(2):148-152
Plasma enhanced chemical vapor deposition (PECVD) is applied to deposit boron silicate glasses (BSG) acting as boron diffusion source during the fabrication of n‐type silicon solar cells. We characterize the resulting boron‐diffused emitter after boron drive‐in from PECVD BSG by measuring the sheet resistances Rsheet,B and saturation current densities J0,B. For process optimization, we vary the PECVD deposition parameters such as the gas flows of the precursor gases silane and diborane and the PECVD BSG layer thickness. We find an optimum gas flow ratio of SiH4/B2H6= 8% and layer thickness of 40 nm. After boron drive in from these PECVD BSG diffusion sources, a low J0,B values of 21 fA/cm2 is reached for Rsheet,B = 70 Ω/□. The optimized PECVD BSG layers together with a co‐diffusion process are implemented into the fabrication process of passivated emitter and rear totally diffused (PERT) back junction (BJ) cells on n‐type silicon. An independently confirmed energy conversion efficiency of 21.0% is achieved on 15.6 × 15.6 cm2 cell area with a simplified process flow. This is the highest efficiency reported for a co‐diffused n‐type PERT BJ cell using PECVD BSG as diffusion source. A loss analysis shows a small contribution of 0.13 mW/cm2 of the boron diffusion to the recombination loss proving the high quality of this diffusion source. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
362.
Lambert C Risko C Coropceanu V Schelter J Amthor S Gruhn NE Durivage JC Brédas JL 《Journal of the American Chemical Society》2005,127(23):8508-8516
We have investigated three organic mixed-valence systems that possess nearly identical inter-redox site distances and differ by the nature of the bridging units benzene, naphthalene, and anthracene: the N,N,N',N'-tetra(4-methoxyphenyl)-1,4-phenylenene-diamine radical cation (1+), the 1,4-bis(N,N-di(4-methoxyphenyl)-amino)naphthalene radical cation (2+), and the 9,10-bis(N,N-di(4-methoxyphenyl)amino)anthracene radical cation (3+). The electronic interactions in these systems have been studied by means of gas-phase ultraviolet photoelectron spectroscopy, vis/NIR spectroscopy, and electronic-structure calculations. The experimental and theoretical results concur to indicate that the strength of electronic interaction decreases in the following order of bridging units: benzene > naphthalene > anthracene. This finding contradicts the usual expectation that anthracene is superior to benzene as a driving force for electronic communication. We explain these results in terms of a super-exchange mechanism and its strong dependence on steric interactions. 相似文献
363.
Vincent Rapinel Cyrille Santerre Farnaz Hanaei Justine Belay Nadine Vallet Njara Rakotomanomana Alain Vallageas Farid Chemat 《Comptes Rendus Chimie》2018,21(6):590-605
The potential of liquefied gases, n-butane, dimethyl ether, and HFO-1234ze as effective and green alternative solvents to substitute hexane has been evaluated for the extraction of aromatic compounds from dry lavender flowers (Lavandula angustifolia Mill.) and fresh orange peels (Citrus sinensis (L.) Osbeck). The performance of these liquefied gases as solvents has been evaluated in terms of yield, olfactory perception, and composition of the extract and also in terms of energy used, green and economic impacts, and regulatory issues. First, a predictive evaluation of the solvation performance of each solvent was carried out using simulations with the conductor-like screening model for real solvent. Then solid–liquid extractions were performed using liquefied gases at a laboratory scale to determine the extraction yield, the chemical composition, and the olfactory perception of each extract. Finally, the applicability of liquefied gas extractions in an industrial process was assessed, taking into account the potential impact on process, quality, safety, regulation, and environment. 相似文献
364.
365.
Gas-phase photoelectron spectroscopy and density functional theory have been utilized to investigate the interactions between the p orbitals of dithiolate ligands and d orbitals of titanium in bent titanocene complexes as minimum molecular models of active site features of pyranopterin Mo/W enzymes. The compounds Cp(2)Ti(S-S) [where (S-S) is 1,2-ethenedithiolate (S(2)C(2)H(2)), 1, 1,2-benzenedithiolate (bdt), 2, or 1,3-propanedithiolate (pdt), 3, and Cp(-) is cyclopentadienyl] provide access to a formal 16-electron d(0) electronic configuration at the metal. A "dithiolate-folding-effect" involving an interaction of metal and sulfur orbitals is demonstrated in complexes with arene- and enedithiolates. This effect is not observed for the alkanedithiolate in complex 3. 相似文献
366.
Klein O Aguilar-Parrilla F Lopez JM Jagerovic N Elguero J Limbach HH 《Journal of the American Chemical Society》2004,126(37):11718-11732
Using dynamic solid state (15)N CPMAS NMR spectroscopy (CP = cross polarization, MAS = magic angle spinning), the kinetics of the degenerate intermolecular double and quadruple proton and deuteron transfers in the cyclic dimer of (15)N labeled polycrystalline 3,5-diphenyl-4-bromopyrazole (DPBrP) and in the cyclic tetramer of (15)N labeled polycrystalline 3,5-diphenylpyrazole (DPP) have been studied in a wide temperature range at different deuterium fractions in the mobile proton sites. Rate constants were measured on a millisecond time scale by line shape analysis of the doubly (15)N labeled compounds, and by magnetization transfer experiments on a second timescale of the singly (15)N labeled compounds in order to minimize the effects of proton-driven (15)N spin diffusion. For DPBrP the multiple kinetic HH/HD/DD isotope effects could be directly obtained. By contrast, four rate constants k(1) to k(4) were obtained for DPP at different deuterium fractions. Whereas k(1) corresponds to the rate constant k(HHHH) of the HHHH isotopolog, an appropriate kinetic reaction model was needed for the kinetic assignment of the other rate constants. Using the model described by Limbach, H. H.; Klein, O.; Lopez Del Amo, J. M.; Elguero, J. Z. Phys. Chem. 2004,218, 17, a concerted quadruple proton-transfer mechanism as well as a stepwise consecutive single transfer mechanism could be excluded. By contrast, using the kinetic assignment k(2) approximately k(3) approximately k(HHHD) approximately k(HDHD) and k(3) approximately k(HDDD) approximately k(DDDD), the results could be explained in terms of a two-step process involving a zwitterionic intermediate. In this mechanism, each reaction step involves the concerted transfer of two hydrons, giving rise to primary kinetic HH/HD/DD isotope effects, whereas the nontransferred hydrons only contribute small secondary effects, which are not resolved experimentally. By contrast, the multiple kinetic isotope effects of the double proton transfer in DPBrP and of the triple proton proton transfer in cyclic pyrazole trimers studied previously indicate concerted transfer processes. Thus, between n = 3 and 4 a switch of the reaction mechanism takes place. This switch is rationalized in terms of hydrogen bond compression effects associated with the multiple proton transfers. The Arrhenius curves of all processes are nonlinear and indicate tunneling processes at low temperatures. In a preliminary analysis, they are modeled in terms of the Bell-Limbach tunneling model. 相似文献
367.
López-Pérez JL Erazo S Delporte C Negrete R Muñoz O García R Backhouse N San Feliciano A 《Magnetic resonance in chemistry : MRC》2005,43(11):943-947
Two new dammarane triterpenoids, 20R,21-epoxydammar-24-ene-3,23-dione and 20R,21-epoxy-3beta-hydroxydammar-24-ene-23-one have been isolated from the aerial parts of Kageneckia angustifolia D. Don, Rosaceae, along with the previously reported triterpenoids oleanolic acid and 3beta-(beta-D-glucosyloxy)-16alpha,23alpha-epoxycucurbita-5,24-dien-11-one and the phenolic prunasin. The structures of these compounds were established by MS, 1D- and 2D-NMR experiments, and the structure of the new compounds were confirmed by X-ray diffraction analysis. 相似文献
368.
Nadine E. Poitiers Luisa Giarrana Volker Huch Michael Zimmer David Scheschkewitz 《Chemical science》2020,11(30):7782
Taking advantage of pendant tetrylene side-arms, stable unsaturated Si6 silicon clusters (siliconoids) with the benzpolarene motif (the energetic counterpart of benzene in silicon chemistry) are successfully employed as ligands towards Group 9 metals. The pronounced σ-donating properties of the tetrylene moieties allow for sequential oxidative addition and reductive elimination events without complete dissociation of the ligand at any stage. In this manner, either covalently linked or core-expanded metallasiliconoids are obtained. [Rh(CO)2Cl]2 inserts into an endohedral Si–Si bond of the silylene-functionalized hexasilabenzpolarene leading to an unprecedented coordination sphere of the Rh centre with five silicon atoms in the initial product, which is subsequentially converted to a simpler derivative under reconstruction of the Si6 benzpolarene motif. In the case of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) a similar Si–Si insertion leads to the contraction of the Si6 cluster core with concomitant transfer of a chlorine atom to a silicon vertex generating an exohedral chlorosilyl group. Metallasiliconoids are employed in the isomerization of terminal alkenes to 2-alkenes as a catalytic benchmark reaction, which proceeds with competitive selectivities and reaction rates in the case of iridium complexes.Unprecedented metallasiliconoids are accessible from a silylene-substituted Si6 siliconoid and Group 9 metal fragments. The isomerization of terminal alkenes to 2-alkenes is competitively catalyzed by these species ( = silicon). 相似文献
369.
The electronic structure of derivatives of VO(acac)(2) is probed using gas-phase UV-photoelectron spectroscopy [acac = 2,4-pentanedione]. The effect on the metal center of electron-donating and -withdrawing groups on the acac ligands is examined. Ionizations from metal-based, acac-based, and V=O-based orbitals are clearly observed. We find that changes at the ligand periphery lead to equivalent changes in the energies of the metal-based and ligand-based ionizations. Additionally, we find that a linear correlation exists between the ionization energies of the metalated complexes and the pK(a) values of the free ligands, indicating that the pK(a) is a good indication of the overall electron-donating abilities of acac ligands. 相似文献
370.
Blanchard JE Elowe NH Huitema C Fortin PD Cechetto JD Eltis LD Brown ED 《Chemistry & biology》2004,11(10):1445-1453
The causative agent of severe acute respiratory syndrome (SARS) has been identified as a novel coronavirus, SARS-CoV. The main proteinase of SARS-CoV, 3CLpro, is an attractive target for therapeutics against SARS owing to its fundamental role in viral replication. We sought to identify novel inhibitors of 3CLpro to advance the development of appropriate therapies in the treatment of SARS. 3CLpro was cloned, expressed, and purified from the Tor2 isolate. A quenched fluorescence resonance energy transfer assay was developed for 3CLpro to screen the proteinase against 50,000 drug-like small molecules on a fully automated system. The primary screen identified 572 hits; through a series of virtual and experimental filters, this number was reduced to five novel small molecules that show potent inhibitory activity (IC50 = 0.5-7 microM) toward SARS-CoV 3CLpro. 相似文献