期刊
ACS APPLIED ENERGY MATERIALS
卷 5, 期 6, 页码 7600-7616出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsaem.2c01059
关键词
Double-donor triphenylamine-phenoxazine core; multi-anchors; open-circuit voltage; electron diffusion; dye electronegativity
资金
- Ministry of Research, Innovation and Digitization, CNCS/CCCDI-UEFISCDI within PNCDI III [PN-III-P2-2.1-PED-2016-0510, 59PED/2017, PN-III-P2-2.1-PED-2019-3520, 438PED/2020]
The attachment of cyanoacrylic acid acceptor groups to the donor core leads to a negative shift in the molecular orbitals of the dye, affecting electron diffusion and electron interception by the electrolyte, resulting in a decrease in the open-circuit voltage of dye-sensitized solar cells.
Four dyes consisting of a phenoxazine-triphenylamine double-donor assembly, on which one to four cyanoacrylic acid acceptor groups were grafted, have been synthesized and characterized. The UV-vis measurements revealed a complex intramolecular charge transfer, a feature supported by the density functional theory calculations. We found that both highest occupied molecular orbitals and lowest unoccupied molecular orbitals negatively shift as more anchors are attached to the donor core, leading to an increase of the dye Mulliken absolute electronegativity. Dye-sensitized solar cell batches impregnated with two different electrolytes have been fabricated with the dyes. Their open-circuit voltage was found to decrease with the increase in the anchor number due to the electron interception by the electrolyte. The dye participation in the electron interception is deduced from the Bode diagrams and the dark current analysis. Moreover, the Nyquist spectra revealed that the dye structure affects the electron diffusion in TiO2. We show that the dye absolute electronegativity is responsible for the modulation of electron diffusion, which stands for the mechanism by which the dye structure catalyzes the electron interception by the electrolyte. Consequently, the increase of the Mulliken dye electronegativity as more anchors are attached to the donor core is identified as the cause of the open-circuit voltage degradation observed experimentally.
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