title: Thiocyanate-free ruthenium(II) sensitizers for dye-sensitized solar cells based on the cobalt redox couple.
abstract: Two thiocyanate-free ruthenium(II) sensitizers, TFRS-41 and TFRS-42, with distinctive dialkoxyphenyl thienyl substituents were successfully prepared and tested for potential applications in making dye-sensitized solar cells (DSCs). Subsequent device fabrication was conducted by using a [Co(bpy)3 ](2+/3+) -based (bpy=2,2'-bipyridine) electrolyte, for which the best performance data, namely, JSC =13.11 mA cm(-2) , VOC =862 mV, fill factor=0.771, and η=8.71%, were recorded for the sensitizer TFRS-42 with a 2,6-dialkoxyphenyl substituent under AM 1.5G irradiation. The markedly higher Voc value was confirmed by the longer electron lifetime revealed in transient photovoltage (TPV) measurements versus the TFRS-1 sensitizer. In addition, DFT calculation and detailed first-principles computational analysis were conducted to provide a rationale for the observed trends in their photovoltaic performances and electron lifetimes, with reference to different performances exhibited by three thiocyanate-free sensitizers, TFRS-1, TFRS-41 and TFRS-42, versus Z907 reference. Through the proper control of peripheral substituents, the thiocyanate-free ruthenium(II)-based DSC sensitizers can positively influence the performances of DSCs, with better light-harvesting capability and suppressed charge recombination, for DSC cells fabricated by using a [Co(bpy)3 ](2+/3+) -based electrolyte.
authors.affiliation: Department of Chemistry and Low Carbon Energy Research Center, National Tsing Hua University, Hsinchu 30013 (Taiwan); Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Ecole polytechnique fédérale de Lausanne, 1015 Lausanne (Switzerland).
authors.forename: Kuan-Lin
authors.initials: KL
authors.lastname: Wu
authors.forename: John N
authors.initials: JN
authors.lastname: Clifford
authors.forename: Sheng-Wei
authors.initials: SW
authors.lastname: Wang
authors.forename: Yella
authors.initials: Y
authors.lastname: Aswani
authors.forename: Emilio
authors.initials: E
authors.lastname: Palomares
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Lobello
authors.forename: Edoardo
authors.initials: E
authors.lastname: Mosconi
authors.forename: Filippo
authors.initials: F
authors.lastname: De Angelis
authors.forename: Wan-Ping
authors.initials: WP
authors.lastname: Ku
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: Mohammad K
authors.initials: MK
authors.lastname: Nazeeruddin
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
mesh_terms: D001393:Azoles / Q000138:chemical synthesis* / Q000737:chemistry; D011211:Electric Power Supplies; D055664:Electrochemical Techniques; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D012993:Solar Energy; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D001393:Azoles; D009942:Organometallic Compounds; D011725:Pyridines; D012428:Ruthenium
keywords: cobalt; dyes/pigments; ruthenium; sensitizers; solar cells