| dc.description.abstract | Dye-sensitized solar cells (DSSCs), is one of the hottest research topics in the new photovoltaic technology, due to its low production cost, simple fabrication process, semi-transparent, light weight, colorful, and can be flexible. In a DSSC device, electrolyte is one of the important components, which reduced the dye, carried the hole to the cathode and determined the theoratical open-circuit voltage (Voc). Iodide/triiodide system is the most commonly used electrolyte, however it’s redox potential can not be tuned to be compatible to sensitizers with various highest occupied molecular orbitals (HOMOs) or increase the Voc of devices by structure modification. On the other hand, cobalt complexes have multiple, reversible oxidation states metal center and their redox potentials can be tuned by the ligands. Therefore ccbalt electrolyte is also one of the important research topics in DSSC. In this study, we synthesis three cobalt-based redox couple coded CRC-1, CRC-2 and CRC-3. CRC-1, CRC-2 and CRC-3 don’t absorb any light from 450 nm to 700 nm, no competing absorption with ruthenium sensitizers (eg: CYC-B11H, SJW-B17 and SJW-B18 developed in our lab). The redox potentials of CRC-1, CRC-2 and CRC-3 are 0.40, 0.74, 0.71 V vs. NHE respectly, all higher than HOMOs of Ru-based sensitizers studied in this thesis. The redox potentials of CRC-2 and CRC-3 are lower than that of iodine-based electrolyte. Devices based on CRC-2 or CRC-3 electrolyte will have higher theoretical Voc. Device using CRC-1 electrolyte and SJW-B18 sensitizer achieves Voc of 0.716 V which is lower than that for the device baesd on iodide/iodine electrolyte, due to the electron in TiO2 recombined with cobalt-based electrolye rapidly. On the other hand, device using CRC-2 electrolyte and SJW-B17 sensitizer has good photovoltaic performance: Jsc: 10.63 mA/cm2, Voc: 0.916 V, FF: 0.660, PCE: 6.42%. CRC-3 electrolyte has a appropriate redox potential for CYC-B11H, SJW-B17 and SJW-B18 dyes due to it has a proper driving force to regenerate the dyes as well as provides high theoretical Voc. Device based SJW-B17 and CRC-3 electrolyte has the best photovoltaic performance amongst the devices studied in this thesis, Jsc: 13.36 mA/cm2, Voc: 0.868 V, FF : 0.619 and PCE : 7.19%. | en_US |