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991.
Solar cells are based on the photovoltaic effect of converting solar energy into electric energy. The mechanism for solar cells is divided into steps, that is, electron-hole pair generation by absorption of light in semiconductors, separation of electron-hole pairs by built-in potential, electron-hole recombination, collection of charge carriers by metal electrodes, etc. In this article, the principle and the theories of these basic steps are presented. On the basis of these steps, methods to improve the efficiency for solar cells are discussed. The fabrication process and the situation of currently produced solar cells are also presented. Solar cells having no p-n junction, that is, photoelectrochemical solar cells and MIS solar cells, are discussed from the perspective of low-cost solar cells. 相似文献
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997.
Kazuaki Kuwata Rie Fujita Kengo Hanaya Shuhei Higashibayashi Takeshi Sugai 《Tetrahedron》2018,74(7):740-745
A formal total synthesis of (?)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl2(dppf)?CH2Cl2 catalysis, and the subsequent cyclization by way of intramolecular reductive SmI2-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (?)-hamigeran B. 相似文献
998.
Fluctuating Carbonaceous Networks with a Persistent Molecular Shape: A Saddle‐Shaped Geodesic Framework of 1,3,5‐Trisubstituted Benzene (Phenine) 下载免费PDF全文
Dr. Koki Ikemoto Jennie Lin Ryo Kobayashi Dr. Sota Sato Prof. Dr. Hiroyuki Isobe 《Angewandte Chemie (International ed. in English)》2018,57(28):8555-8559
A saddle‐shaped macromolecule has been synthesized. The molecule was designed as a geodesic saddle with 1,3,5‐trisubstituted benzene (named phenine) as the fundamental unit. The phenines were woven into a polygonal framework that was composed of 168 sp2‐hybridized carbon atoms. The saddle‐shaped structure with unique symmetry showed atypical conformational changes. The biaryl linkages in this molecule had a small energy barrier for rotation, and these structural fluctuations resulted in seven 1H NMR resonances representing 84 aromatic hydrogen atoms. Nevertheless, the overall saddle shape of the molecule was persistent, and the “up” and “down” orientations of phenine moieties circulated to give average 1H resonances. The structural characteristics of this molecule, including the anomalous entropy‐driven dimerization, may deepen our understanding of defect‐rich graphitic sheets. 相似文献
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Matsuta K. Minamisono T. Tanigaki M. Fukuda M. Nojiri Y. Mihara M. Onishi T. Yamaguchi T. Harada A. Sasaki M. Miyake T. Minamisono K. Fukao T. Sato K. Matsumoto Y. Ohtsubo T. Fukuda S. Momota S. Yoshida K. Ozawa A. Kobayashi T. Tanihata I. Alonso J. R. Krebs G. F. Symons T. J. M. 《Hyperfine Interactions》1996,97(1):519-526
The magnetic moments of the proton drip-line nuclei13O(I
= 3/2–,T
1/2 = 8.6 ms) and 9C(I
= 3/2–,T
1/2 = 126 ms) have been determined for the first time through the combined techniques of polarized radioactive nuclear beams and-NMR detection. The observed magnetic moments are ¦(13O)¦ = 1.3891 ±0.0003
N and ¦(9C)¦ = 1.3914 ±0.0005
N. Spin expectation values are deduced to be 0.76 and 1.44 for13O and9C, respectively. While the of13O is consistent with the systematics from isospinT= 1/2 mirror pairs, the of9C is unusually large, even far larger than the single particle value, = 1. 相似文献