Molecular Engineering of 2-Quinolinone Based Anchoring Groups for Dye-Sensitized Solar Cells
Six new donor-pi spacer-acceptor (D-pi-A) organic sensitizers based on the 2-quinolinone moiety as acceptor and anchoring groups were synthesized and tested for their performance in dye-sensitized solar cells (DSSCs). The systematic tuning of acceptor strength and anchoring modes lead to a variation of the photoelectrochemical properties and device performances. Characterization of the molecular structure and electronic and optical properties of the dyes, as well as their photovoltaic performance in DSSCs, was accomplished by means of NMR, UV spectroscopy, electrochemistry, quantum chemical, Fourier transform infrared spectroscopy, and transient photovoltage decay techniques. Thereby, significant dependence of DSSC performance on the substituents and anchoring groups was observed. In general, the optoelectronic properties of the sensitizers were mainly governed by the 2-quinolinone acceptor segment. Different types of anchoring modes were employed in this new type of acceptor segment, and their significance in the solar conversion efficiency was analyzed. Amide N,O-chelating anchoring mode and bianchor-type anchoring mode show higher short circuit current density among the various anchoring groups. This new type of anchoring mode will emerge as a promising alternative anchoring group to the widely utilized cyanoacrylic acid group.