Dye regeneration and charge recombination in dye-sensitized solar cells with ferrocene derivatives as redox mediators
Torben Daeneke,a Attila J. Mozer,b Tae-Hyuk Kwon,c Noel W. Duffy,d Andrew B. Holmes,c Udo Bach*e and Leone Spiccia*a
a School of Chemistry, ARC Centre of Excellence for Electromaterials Science, Monash University, Australia
E-mail: Leone.Spiccia@Monash.edu
b Intelligent Polymer Research Institute, ARC Centre for Excellence for Electromaterials Science, University of Wollongong, Wollongong, Australia
c School of Chemistry, Bio21 Institute, University of Melbourne, Australia
d CSIRO Energy Technology, Clayton, Australia
e Department of Materials Engineering, Monash University, Australia
E-mail: Udo.Bach@Monash.edu
Ferrocene compounds are promising redox shuttles for application in dye-sensitized solar cells (DSCs). Chemical modification of the cyclopentadienyl rings is easily achievable affording almost unlimited variation of the redox properties. This allows fine-tuning of the driving force for dye-regeneration and optimization of the energy conversion efficiency of DSCs. Herein, six ferrocene derivatives have been chosen for investigation which cover the large redox potential range of 0.85 V, by virtue of simple alkylation and halogenation of the cyclopentadienyl ring, and enable improved matching of the energy levels of the sensitizer and the electrolyte. Although the focus of this work was to examine the effect of the redox potential on charge transfer processes, DSCs were fabricated which achieved high energy conversion efficiencies of over 5%. Charge transfer reactions were studied to reveal the dependence of the dye regeneration rate, recombination losses and recombination pathways on the reaction driving force. An increase in redox potential led to a higher efficiency due to higher open circuit potentials until a threshold is reached. At this threshold, the driving force for dye regeneration (18 kJ mol−1, ΔE = 0.19 V) becomes too small for efficient device operation, leading to rapid recombination between the oxidized dye and electrons in the TiO2 conduction band. As a result of this work guidelines can be formulated to aid the selection of redox couples for a particular sensitizer in order to maximize the utilization of incident solar energy.
This article is part of the themed collection: RACI100: Celebrating Australian Chemistry
The article was received on 02 Feb 2012, accepted on 28 Feb 2012 and first published on 29 Feb 2012
DOI: 10.1039/C2EE21257A
Download Citation: Energy Environ. Sci., 2012,5, 7090-7099
T. Daeneke, A. J. Mozer, T. Kwon, N. W. Duffy, A. B. Holmes, U. Bach and L. Spiccia, Energy Environ. Sci., 2012, 5, 7090
Torben Daeneke
Attila J. Mozer
Tae-Hyuk Kwon
Noel W. Duffy
Andrew B. Holmes
Udo Bach
Leone Spiccia