1. Development of Novel Ferrocene-Containing BODIPY Dyes for
Light Harvesting Applications
Paloma Prieto, Burhan Hussein, Jennifer Huynh, Malek El-Aooiti, Bryan D. Koivisto*
Department of Chemistry and Biology. Ryerson University, 350 Victoria Street, Toronto ON, Canada, M5B 2K3
4th Annual Ryerson Science Symposium Wednesday August 19th, 2015
Facing the global energy demand
The high energy requirements of the 21st century have made it necessary to explore
renewable energy sources as a replacement for fossil fuels. In an effort to reduce
environmental pollution and address climate change, solar energy has become
increasingly significant.
To scale with the map, this is the surface area
needed to be covered by solar panels (at 20%
efficiency) to supply the increased global
energy demand projected for 2030 (22.7 TW):1
Shown is a proposed allocation of this area
according to energy use distribution.
Solar power vastly exceeds global energy requirements .
Dye-sensitized solar cells (DSSCs) Chromophore design
Ferrocene is a good electron
donor and provides redox stability
without competing against
BODIPY for photon absorption
Acetylene bridge
relieves steric
strain, allowing for
successful synthesis
BODIPY encourages
light absorption and
charge transfer
Cyanoacetic acid accepts the
excited electron density and
anchors the dye to TiO2
Tunable phenyl
group increases
solubility
Additional acceptors studied:
Aldehyde Malonitrile
DONOR π-SPACER ACCEPTOR
Synthetic pathway
A considerable number of D-π-A dyes containing
ferrocene and BODIPY (4,4-difluoro-4-bora-3a,4a-
diaza-s-indacene) can be prepared.
This project focuses on the synthesis and
characterization of dyes involving the following 4 R-
group substituents:
Reference electron-
donating
electron-
withdrawing
Apart from mildly tuning the orbital energies of the
dyes, the phenyl rings lie orthogonal to the BODIPY
core and interrupt π- stacking interactions which
otherwise cause serious solubility issues.
This next-generation photovoltaic
technology is cheaper than traditional
silicon solar cells and has efficiencies
upwards of 10%. The transparency of the
devices also makes them useful for
windows and other applications.2
In the device, light absorbed by the dye
excites an electron into a higher energy
state (1) and allows it to be injected into the
conduction band of TiO2 (2). It travels to
the conducting glass anode (3), along the
circuit, and back to a platinum cathode. An
electrolyte then regenerates the original
dye (4, 5).
An electron push-pull molecule is ideal for DSSC applications:
Light absorption profiles
The extended π-conjugation of the dyes and the use of the BODIPY core, which is
well known as an intense absorber, result in panchromatic dyes.
Electrochemistry
Cyclic voltammetry shows a reversible oxidation process ensuring that the dye can
be regenerated once it has given up an electron.
Frontier molecular orbitals
Conclusions and future work
References
1Surface Area Required to Fuel the World With Solar.
http://landartgenerator.org/blagi/archives/127 (Accessed Aug 7th, 2015).
2Basic Research Needs for Solar Energy Utilization, U.S. Department of Energy Office of
Basic Energy Sciences, Apr 21, 2005.
0.0E+00
2.0E+04
4.0E+04
350 450 550 650 750
MolarAbsorptivity,ε(M-1cm-1)
Wavelength, λ (nm)
UV-Vis spectra of ferrocene-BODIPY-aldehyde family
-25
-5
15
35
55
0.25 1 1.75
Current(μA)
Applied Voltage (V vs. NHE)
Characteristic cyclic voltammogram of ferrocene-containing
BODIPY dyes
first oxidation
½ wave potential
(0.90 V)
HOMO -1
HOMO
LUMO
LUMO + 1
This project describes the successful ongoing synthesis and characterization of a new
ferrocene-BODIPY dye family. These molecules exhibit broad light absorption profiles,
distinct electron density shifts between the ground and excited states, and good redox
reversibility. DSSC device testing and optimization is needed to verify the dye
performance.
Density Functional Theory (DFT)
calculations show a desirable shift
of electronic density from the
donor, through the π-spacer, to
the acceptor region upon
excitation.
The dominant electronic transition
evidenced in the light absorption
profile is HOMO-1 to LUMO.
Charge separation in the excited
state encourages electron
injection into the TiO2 conduction
band. This reduces the probability
of electron relaxation back to the
ground state.
1a 30%
b 30%
c 48%
d 30%
2a 73%
b 42%
c 74%
d 66%
3a 35%
b 43%
c 48%
d 77%
4c 51%
5b 28%
c 33%
a b c d