The Effect of Pyridyl Nitrogen Atom Position in Pyrido-[3,4-b]pyrazines in Donor-Acceptor-pi-Acceptor Dyes on Absorption, Energy Levels, and Photovoltaic Performances of Dye-Sensitized Solar Cells

• A donor-acceptor-pi-acceptor (D-A-pi-A)-type organic dye (DTN-1) incorporating a pyrido[3,4-b]pyrazine (PP) unit with the pyridyl N atom adjacent to the anchoring group has been synthesized for use in dye-sensitized solar cells (DSSCs). The maximum absorption wavelength of DTN-1 was clearly red-shifted compared with dye DT-1, based on PP unit with the pyridyl N atom adjacent to the donor group. However, this change of structure has a negative effect on photovoltaic performances, and devices made with DTN-1 only reached a power conversion efficiency of 6.10% under AM1.5G irradiation compared with 8.57% achieved by DT-1. Density functional theory calculations suggest that DTN-1 has a smaller oscillator strength, which is connected to its relatively low light-harvesting efficiency. In addition, the results of electrochemical impedance spectroscopy (EIS) reveal that charge recombination in DSSCs based on DTN-1 is more than that in the counterpart DT-1, thus leading to a lower open-circuit voltage (V-oc).

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

donor-acceptor-pi-acceptor dyes

dye-sensitized solar cells

molecular engineering

nitrogen

pyrido[3

4-b]pyrazines

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