Synthesis of an Organic Dye for Dye-sensitized Solar Cells

The organic molecules with D–π–A structures have attracted increasing attention since they can serve as electro active and photoactive materials in molecular electronics [1]. Recently, more and more attention has been directed to the application of metal-free organic dyes in DSSCs [2]. In this work, new metal free dye is reported and its optical, electrochemical, photovoltaic properties and structural relationships are investigated in detail. The general procedure for preparing metal free organic dye is given in Figure 1. The absorption spectrum of dye in CH3CN has three distinct absorption bands at around 288, 320 and 395 nm, respectively. The absorption peaks at around 320 nm correspond to the π→π* electron transition of the conjugated molecule; and the absorption peaks at around 385 nm can be assigned to an intramolecular charge transfer between the phenothiazine-based donor and the cyanoacrylic acid [2], providing efficient charge-separation at the excited state. The λmax of dye adsorbed on a TiO2 film is 419.5 nm. Upon dye adsorption on to a TiO2 surface, the wavelength of maximum absorption is bathochromically shifted by 24.5 as compared to the corresponding spectra in solution, implying that dye adsorbed on to TiO2 surface contain partial J-type aggregates. The DSSCs were prepared and compared to investigate the relationships between the sensitizing behavior of dye molecule and its structures. The solar-energy-to-electricity conversion efficiency (η) of the DSSCs is 5.32 %