Novel Alizarin Palladacyclic Complexes as Sensitizers in High Durable Dye-Sensitized Solar Cells,370. Mahmood Taki, Behzad Rezaei, Ali A Ensafi, Kazem Karami, Sedigheh Abedanzaheh, Najme Fani, Polyhedron, 2016, 109, 40-46.
Palladacyclic complexes are new organometallic compounds of Pd with numerous applications in synthesis of materials. In this study, mono and dinuclear complexes of Alizarin have been synthesized and used as novel photo-sensitizers in dye-sensitized solar cells (DSSCs). A suitable interaction between the dyes and TiO2 nanoparticles represented with the results of optical spectra of the proposed complexes recorded in solution and adsorbed on TiO2 film. On the basis of cyclic voltammetry analysis, the oxidized state of dinuclear complex is more stable than mononuclear one that confirmed with the spectro-electrochemical studies. One of the important parameters in a solar cells performance is stability in high temperature conditions. Heat treatment step during sealing process (up to 140 °C) and elevated temperature in sunlight (up to 70 °C) could decrease the DSSC performance due to the decomposition or structural changing of the sensitizer. Thermal stability study of the DSSCs with palladacyclic complexes as sensitizer showed possibility of making high durable solar cells. A 20% decay in short circuit photo-current density (JSC) were observed in 130 ± 5 °C for mono-nuclear complex and in 93 ± 2 °C for dinuclear one and up to 200 °C insignificant decrease obtained in open circuit voltage (VOC) of the palladacyclic sensitized solar cells. Hence, it was found that the same performance decay was obtained in 71 ± 5 °C for JSC and in 147 ± 3 °C for VOC in the case of N719 as a standard dye. Also, long-term stability test of the solar cells under continuous illumination, showed an improvement of about 20% in current density delivered by the solar cell sensitized with mono-nuclear complex related to the cell fabricated with the standard dye. Finally, the density functional theory (DFT) calculations were used to consider the electron displacement during excitation of the complexes. The results were in agreement with the experimental observations.