| dc.description.abstract | The study of osmium complexes for dye-sensitized solar cells (DSCs) is extremely rare. However, heavy atom effect can endow osmium complexes with efficient absorption capacity at near infrared region, having the opportunity to expand the spectral response for the sensitized cells and to increase the short-circuit current density. In this study, based on CYC-33O, two new osmium complex dyes (coded CYC-45Cl and CYC-45I) were synthesized. The molecular design for improving light-harvesting ability of osmium complexes and exploring the heavy atom effect is substituting 2-methylthiophene at the 4-position of pyridine of the anchoring ligand, attaaching Hexyl-EDOT at the 4,4′ positions of the ancillary bipyridine ligands, and using respectively chloride and iodide as monodentate. For the preparation of CYC-45Cl, three synthesis conditions were tested. It was finally found that the conditions of using n-butanol and ethylene glycol as solvent for coordinating the anchoring and ancillary ligands respectively. 40 eq. of potassium hydroxide and tetrahydrofuran were apprpriate for the hydrolysis. For CYC-45I, (TBA)2OsI6 were preparing by (NH4)2OsCl6 and hydriodic acid were used as the starting material for the coordination, followed by the similar synthesis conditions as those for CYC-45Cl. Practically, the reaction time for CYC-45I was prolonged (16 h) with higher temperature of 195 oC, and then 5 eq. of potassium hydroxide and tetrahydrofuran were used for hydrolysis. Owing to the highly conjugating anchoring ligand, CYC-45 series of osmium complexes display that the absorption coefficient and wavelength range are both superior to those of CYC-33O. Among them, CYC-45Cl shows the highest absorption coefficient (30900 M-1 cm-1) at 548 nm and the broadest absorption band (onset of 941 nm). Compared with CYC-45Cl and CYC-33O, the IPCE spectrum of CYC-45I sensitized device shows the best conversion of photon to current, which attribute to the highest Jsc value of 11.38 mA cm-2. The device based on CYC-45I also provide the highest Voc value of 531 mV and the best power conversion efficiency (PCE) of 4.11%, which should be ascribed to that the removal of sulfur atoms in CYC-33O could reduce charge recombination. After preliminary optimization of device fabrication condition (the number of TiO2 layers and the concentration of BMII in electrolyte), the PCE based on CYC-45I increased to 4.24%, and 4.76%, respectively. These results indicate the high application potential of CYC-45I. | en_US |