Synthesis and photoelectric properties of coumarin type sensitizing dyes

Abstract

Two novel coumarin type sensitizing dyes were synthesized with coumarin group bearing electron-donating group as donor, thiophene as π bridge and cyanoacetic acid as acceptor. Their spectral, electrochemical and photoelectric properties were evaluated. The results suggest that both dyes have the molecular orbital energy matched with the conduction band of TiO2 and the redox potential of the electrolyte I2/I-, which ensures the production of the current cycle in the cell. Compared with 2-cyano-3-[5-(7-methoxy-2-oxo-2H-chromen-3-yl)thiophen-2-yl] acrylic acid (IIIb) bearing methoxy group, sensitizing dye 2-cyano-3-[5-(7-diethylamino-2-oxo-2H-chromen-3-yl)thiophen-2-yl] acrylic acid (IIIa) bearing diethylamino group on C-7 of coumarin ring shows improved absorption of intramolecular charge transfer and the red shift of UV spectra. Dye sensitized solar cell (DSSC) based on IIIa has reduced back current and better IPCE (incident photo-to-current conversion efficient) and Jsc, which leads to improved photoelectric conversion efficiency (Jsc=8.68 mA/cm2, Voc=574 mV, η=3.52%). © 2013 Chinese Chemical Society & SIOC, CAS.