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.

Ruthenium and Osmium Complexes That Bear Functional Azolate Chelates for Dye‐Sensitized Solar Cells

“…The DSSC device fabricated using TFRS-41 and TFRS-42 sensitizers and [Co(bpy) 3 ] 2 + /3 + electrolyte afforded performances of J SC = 9.42 mA cm À2 , V OC = 864 mV,F F = 0.778, and h = 6.33 % as well as J SC = 13.11mAcm À2 , V OC = 862 mV,F F = 0.771, and h = 8.71 %, respectively. [47] The large difference in J SC of 3.69 mA cm À2 between TFRS-41 and TFRS-42 has to be attributed to the steric influence, because both sensitizers exhibit essentially identical spectroscopic and electrochemical properties. Figure 7s hows the transient photocurrent as af unction of incident light intensity for the relevantd evices.…”

New Members of the Deutsche Akademie der Naturforscher Leopoldina / Teacher of the Year at SCIENCE Award: Stephan P. A. Sauer / Scientist of the Year Prize, University of Frankfurt: H. Schwalbe / Lorenz Oken Medal: H.‐J. Quadbeck‐Seeger / Normann Medal: U. T. Bornscheuer / Wöhler–BASF Early‐Career Prize: M. Walter / Eni Award for New Frontiers in Hydrocarbons: A. H. Hoveyda / Nemitsas Prize and Einstein Professorship: K. C. Nicolaou

“…Michael Grätzel (EPFL) was featured here when he won the Albert Einstein World Award of Science 2a. He has recently reported in ChemSusChem on thiocyanate‐free ruthenium(II) sensitizers 2b. Grätzel is Co‐Chair of the Editorial Advisory Board of ChemPhysChem , and is also on the International Advisory Boards of Angewandte Chemie and ChemSusChem…”

Neue Mitglieder der Deutschen Akademie der Naturforscher Leopoldina / Preis für den Dozenten des Jahres in den Naturwissenschaften: Stephan P. A. Sauer / Preis für den Wissenschaftler des Jahres an der Universität Frankfurt: H. Schwalbe / Lorenz‐Oken‐Medaille: H.‐J. Quadbeck‐Seeger / Normann‐Medaille: U. T. Bornscheuer / Wöhler‐BASF‐Nachwuchspreis: M. Walter / Eni‐Preis für Kohlenwasserstoff‐Forschung: A. H. Hoveyda / Nemitsas‐Preis und Einstein‐Professur: K. C. Nicolaou

“…Michael Grätzel (EPFL) wurde in dieser Rubrik vorgestellt, als ihm der Albert Einstein World Award of Science verliehen worden war 2a. Vor kurzem hat er in ChemSusChem thiocyanatfreie Ruthenium(II)‐Sensibilisatoren beschrieben 2b. Grätzel ist einer der Vorsitzenden des Editorial Advisory Board von ChemPhysChem und gehört außerdem den Internationalen Beiräten der Angewandten Chemie und von ChemSusChem an…”