title: Iodide-free ionic liquid with dual redox couples for dye-sensitized solar cells with high open-circuit voltage.
abstract: A novel ionic-liquid mediator, 1-butyl-3-{2-oxo-2-[(2,2,6,6-tetramethylpiperidin-4-yl)amino]ethyl}-1H-imidazol-3-ium selenocyanate (ITSeCN), has been successfully synthesized for dye-sensitized solar cells (DSSCs). ITSeCN possesses dual redox channels, imidazolium-functionalized 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) and selenocyanate, which can serve as the cationic redox mediator and the anionic redox mediator, respectively. Therefore, ITSeCN has a favorable redox nature, which results in a more positive standard potential, larger diffusivity, and better kinetic heterogeneous rate constant than those of iodide. The DSSC with the ITSeCN electrolyte shows an efficiency of 8.38 % with a high open-current voltage (VOC ) of 854.3 mV, and this VOC value is about 150 mV higher than that for the iodide-based DSSC. Moreover, different electrocatalytic materials were employed to trigger the redox reaction of ITSeCN. The ITSeCN-based DSSC with the CoSe counter electrode achieved the best performance of 9.01 %, which suggested that transition-metal compound-type materials would be suitable for our newly synthesized ITSeCN mediator.
authors.affiliation: Department of Chemical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617 (Taiwan).
authors.forename: Chun-Ting
authors.initials: CT
authors.lastname: Li
authors.forename: Chuan-Pei
authors.initials: CP
authors.lastname: Lee
authors.forename: Chi-Ta
authors.initials: CT
authors.lastname: Lee
authors.forename: Sie-Rong
authors.initials: SR
authors.lastname: Li
authors.forename: Shih-Sheng
authors.initials: SS
authors.lastname: Sun
authors.forename: Kuo-Chuan
authors.initials: KC
authors.lastname: Ho
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry; D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012399:Rotation; D012993:Solar Energy; D013499:Surface Properties
chemical_list: D004396:Coloring Agents; D003497:Cyclic N-Oxides; D007093:Imidazoles; D052578:Ionic Liquids; C003959:TEMPO
keywords: dye-sensitized solar cells; electrochemistry; ionic liquids; radicals; redox chemistry