Synthesis of low bandgap small molecules containing fluorinated benzothiadiazole and phenothiazine for photovoltaic applications

ABSTRACT

A series of small molecules (SMs) containing fluorinated benzothiadiazole (BT) and phenothiazine (PT) were synthesized via the Suzuki coupling reaction. For exploring the effect of auxiliary electron-accepting moieties on the chemical structures, one or two fluorine atoms were selectively incorporated into the central electron-withdrawing BT unit of the non-fluorinated standard small molecule (BDP) to afford BDP-F and BDP-FF, respectively. Because of the favorable contributions of the fluorine atoms, the optimized inverted-type photovoltaic devices containing the SMs as active components exhibited improvement in PCE with increasing fluorine substitution, i.e., 0.49%, 0.54%, and 0.78% for BDP, BDP-F, and BDP-FF, respectively.

KEYWORDS:

• Benzothiadiazole
• fluorine
• phenothiazine
• photovoltaic
• small molecules

Acknowledgment

This research was supported by a Research Grant of Pukyung National University (2016 year).