Charge Separation in a Nonfluorescent Donor−Acceptor Dyad Derived from Boron Dipyrromethene Dye, Leading to Photocurrent Generation

Abstract

Boron dipyrromethene (BODIPY), which is commonly used as an energy absorbing and transferring antenna\nmolecule, has been modified to contain an electron donor moiety, 8-(2,4,5-trimethoxyphenyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-<i>s</i>-indacene (<b>MEOPHBDP</b>). The photoinduced electron transfer from\na 2,4,5-trimethoxyphenyl moiety to a BODIPY moiety of <b>MEOPHBDP</b> in acetonitrile was observed by\nfemtosecond laser flash photolysis measurements. The lifetime of the charge-separated state of <b>MEOPHBDP</b>\nwas 59 ps at 298 K. The dye-sensitized solar cells (DSSC) were prepared using <b>MEOPHBDP</b> with carboxylic\nacid (<b>MEOPHBDP</b>−<b>COOH</b>) and a reference BODIPY dye having no electron donor moiety. The photovoltaic\nmeasurements were performed using a standard two-electrode system consisting of a working electrode and\na Pt sputtered electrode in methoxyacetonitrile containing 0.5 M iodide and 0.05 M I<sub>2</sub>. The photoelectrochemical\nproperties of DSSC with <b>MEOPHBDP</b> are compared with those with a reference BODIPY dye.