Enhanced photovoltaic performance of D-π-A organic sensitizers by simple fluorination of acceptor unit

Abstract

A simple and facile molecular modification method is presented to enhance the photovoltaic and photoelectrochemical properties of D-π-A organic sensitizers. This modification is obtained by incorporating fluorine as an additional acceptor unit. By the electron-withdrawing ability of fluorine, the electron transfer to the anchoring group is promoted, which ultimately leads to a decrease in the HOMO-LUMO energy gap. In addition, the incorporated fluorine also induces prominent J-aggregation, resulting in an increase in the dye loading amount on the photoanode. Because of these positive effects, the additional fluorine acceptor enhances both the photocurrent and photovoltage of dye-sensitized solar cells (DSSCs). In particular, electrochemical impedance study reveals that the electron lifetime in the dye-sensitized photoanode also increases by the incorporation of fluorine in the dye molecules, mostly because of enhanced dye loading.