Part I: Synthesis and Study of Excited-State Proton-Transfer Compounds Part II: Organic Dyes Containing the 2,7-Carbazole Moiety for DSSCs
Date Issued
2011
Date
2011
Author(s)
Shen, Jiun-Yi
Abstract
Part I
We have synthesized a series of 7-azaindole (7AI) bearing cyano groups. The interplay between excited-state charge and proton transfer reactions in protic solvents is investigated in a series of 7-azaindole derivatives: 3-cyano-7-azaindole (3CNAI), 5-cyano-7-azaindole (5CNAI), 3,5-dicyano-7-azaindole (3,5CNAI) and dicyanoethenyl-7-azaindole (DiCNAI). Similar to 7AI, 3CNAI and 3,5CNAI undergo methanol catalyzed excited-state double proton transfer (ESDPT), resulting in dual (normal and proton transfer) emission. Conversely, ESDPT is prohibited for 5CNAI and DiCNAI in methanol, as supported by a unique normal emission with high quantum efficiency. Instead, the normal emission undergoes prominent solvatochromism. Detailed relaxation dynamics and temperature dependent studies are carried out. The results conclude that significant excited-state charge transfer (ESCT) takes place for both 5CNAI and DiCNAI. The charge-transfer specie possesses a different dipole moment from that of the proton-transfer tautomer species. Upon reaching the equilibrium polarization, there exists a solvent-polarity induced barrier during the proton-transfer tautomerization, and ESDPT is prohibited for 5CNAI and DiCNAI during the excited-state lifespan. The result is remarkably different from 7AI, which is also unique among most excited-state charge/proton transfer coupled systems studied to date.
Part II
Five new metal-free organic dyes (SJY1–SJY5) containing 2,7-carbazole moieties were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were fully characterized. Electrochemical measurement data indicate that the tuning of the HOMO and LUMO energy levels can be conveniently accomplished by alternating the donor moiety. The liquid electrolyte DSSCs based on the SJY2-sensitized exhibited the
Subjects
7-azaindole
excited-state
charge transfer
proton transfer
2,7-carbazole
aggregation
triarylamines
regeneration
SDGs
Type
thesis
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