Effects of different acceptors in phenothiazine-triphenylamine dyes on the optical, electrochemical, and photovoltaic properties

In dye-sensitized solar cells (DSSCs), as the excited electrons from dye molecules are injected to the conduction band of semiconductor film through the acceptor moieties, the acceptor groups have significant influences on the photovoltaic properties of the dyes. In this paper, the effects of different acceptor groups (cyanoacetic acid and rhodanine-3-acetic acid) in two phenothiazine-triphenylamine dyes (PTZ-1 and PTZ-2) on the optical, electrochemical properties and photovoltaic performances were studied. In comparison with PTZ-2, the photovoltaic performance of PTZ-1 is significantly improved by replacing rhodanine-3-acetic acid to cyanoacetic acid. The conversion efficiency of solar cell based on the PTZ-1 is increased about 110%. The lower efficiency of solar cell based on PTZ-2 is mainly because the delocalization of the excited state is broken between the 4-oxo-2-thioxothiazolidine ring and the acetic acid, which affects the electron injection from PTZ-2 to the conduction band of TiO2.

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► The phenothiazine-triphenylamine organic dyes with different acceptors were studied.
► The absorption of PTZ-2 with rhodanine-3-acetic acid shows an obvious red shift.
► PTZ-1 gives effective and faster electron injection from the LUMO to TiO2 electrode.
► PTZ-1 with cyanoacetic acid as acceptor shows the better photovoltaic performance.