Browsing by Author "Chaurasia, Sumit"

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Benzimidazole/Pyridoimidazole-Based Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells
(2017-05-04)
Chaurasia, Sumit
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Li, Chun-Ting
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Desta, Mulu Berhe
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Ni, Jen-Shyang
;
Lin, Jiann T.
A new series of benzimidazole (BIm)-based dyes (SC32 and SC33) and pyridoimidazole-(PIm) based dyes (SC35, SC36N and SC36) were synthesized as sensitizers for dye-sensitized solar cells (DSSCs). The N-substituent and C-substituent at the BIm and PIm cores were found to be the dominating factor in determining the electronic properties of the dyes and their DSSCs performance. The efficiency of BIm-based dyes (SC35 and SC36) was found to be higher than that of the PIm-based dyes (SC32 and SC33) due to better light harvesting. The C-substituents in SC36, a 4-hexylloxybenzene and a hexyl chain, are beneficial to dark current suppression, and hence SC36 achieves the best efficiency of 7.38% (approximate to 85% of N719). The two BIm dyes have better cell efficiencies than their congeners with a bithiophene entity between the BIm and the anchor due to better light harvesting of the former.
Pyrazine-incorporating panchromatic sensitizers for dye sensitized solar cells under one sun and dimlight
(2018-07-28)
Desta, Mulu Berhe
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Vinh, Nguyen Son
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Kumar, Ch. Pavan
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Chaurasia, Sumit
;
Wu, Wei-Ti
New D-A--A type (D = electron donor, A = auxiliary acceptor, = -conjugated bridge, and A = electron acceptor/anchor) sensitizers with two bis(alkoxy)phenyl substituents incorporating thieno[3,4-b]pyrazines (TP) or a benzo[3,4-b]pyrazine (BP) entity as the auxiliary acceptor have been synthesized for application in dye-sensitized solar cells (DSSCs). Under 1 sun illumination, the DSSCs fabricated from the two BP dyes with a co-adsorbent have efficiencies of 8.39% and 9.03%, respectively. The latter surpasses that of the standard N719 dye (8.87%). Under dim light conditions MD7 exhibited a power conversion efficiency of 18.95% and 27.17% under 300 lux and 6000 lux irradiance, respectively.
Reversed Y-shape di-anchoring sensitizers for dye sensitized solar cells based on benzimidazole core
(2017-05-01)
Desta, Mulu Berhe
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Chaurasia, Sumit
;
Lin, Jiann T.
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應用化學系
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Department of Applied Chemistry
Three new Y-shaped D-(pi-A)(2) di-anchoring organic dyes comprising an arylamine as the electron donor, 2-cyanoacrylic acid as electron acceptors and various 2,4,7-trisubstituted benzimidazole entity as theirlinkers/spacers, have been synthesized for dye-sensitized solar cells. The new dyes MD2 and MD3 show red-shifted absorption in solution spectra when compared with their congeners (8b and 9b) without electron-donating hexyloxy substituents. The N-alkyl at the benzimidazble, though helps with improved solubility, apparently results in serious twist between the benzimidazole core and the neighboring thienyl rings in the conjugated segment connected to the acceptor facing the N-alkyl or the phenyl ring connected to the arylamine donor. Photophysical and electrochemical measurements as well as theoretical computations were carried out on the new dyes. In addition to current voltage scan and incident photon to electron conversion efficiency (IPCE), electrochemical impedance spectroscopic (EIS) studies were also conducted. The dye MD3 exhibited the highest light-to-electric energy conversion efficiencies of 6.45% and 6.69%, respectively, for DSSCs without and with CDCA co-adsorbent. Better cell performance of MD3 than 9b can be attributed to better light harvesting and better dark current suppression of the former. (C) 2017 Elsevier Ltd. All rights reserved.