HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 293
C149 - Nickel Oxide Nanostructured Electrodes for Perylenediimide-Based Dye-
Sensitized Solar Cells
Sebastian Feihl a , Rubén D. Costa a , Stephan Pflock a , Cordula Schmidt b , Susanne Backes b , Jörg
Schönamsgruber b , Andreas Hirsch b , Dirk M. Guldi a
a, Department of Chemistry and Pharmacy, Chair of Physical Chemistry I, Friedrich-Alexander-University Erlangen-Nuremberg,
Egerlandstrasse 3, Erlangen, 91058, DE
b, Department of Chemistry and Pharmacy, Chair of Organic Chemistry II, Friedrich-Alexander-University Erlangen-Nuremberg,
Henkestrasse 42, Erlangen, 91054, DE
In this work we have addressed the grand challenges associated with nickel oxide (NiO)
electrodes as photocathodes in p-type dye-sensitized solar cells (p-DSSCs) and with
perylenediimide (PDIs) as light harvester / electron acceptors.[1, 2] To this end, two
approaches were pursued towards preparing NiO nanoparticle pastes suitable for fabricating
mesoporous electrodes on conductive fluorine doped tin oxide (FTO) glass substrates. Firstly,
commercially available NiO nanoparticles were dispersed in a mixture of ethanol and terpineol.
Here, in order to obtain a mesoporous network two types of ethylcelluloses - EC 5 – 15 and
30 – 50 mPas - were added in a 1:1 weight ratio. After evaporating ethanol, the resulting
pastes were spread on FTOs by doctor blading and tempered at different temperatures.
Importantly, the influence of the calcination temperature was crucial in terms of developing
efficient performing electrodes. Despite all of our efforts, the visual appearance of the
resulting NiO electrodes points towards a strong heterogeneity. To circumvent this obstacle, a
second approach en route towards homogenous electrodes was investigated. In that case,
commercial NiO nanoparticles were mixed with a mixture of EC 5 – 15 and 30 – 50 mPas at 1:1
weight ratio and triacetin as plasticizer in ethanol. In this way, pastes containing 7 wt% of EC,
3 wt% triacetin, and different contents of NiO nanoparticles (i.e., 5 to 20 wt%) were prepared.
Most importantly, the resulting electrodes showed a much improved FTO coverage, which is
corroborated by scanning electron microscopy (SEM) images.
In the next step, a symmetrically functionalized PDI bearing two dendrons with three
carboxylate anchors each was utilized to sensitize the different NiO photoelectrodes. To
interpret our results, a second, non-symmetrically functionalized PDI was used as a reference.
In this particular case, one dendron is replaced by a dodeca-alkyl chain. In addition, key
aspects such as the influence of chenodeoxylcholic acid (Ch-A) as a coadsorbent to prevent
aggregation as well as the time dependence of the PDI uptake were keenly investigated. To
conclude, devices featuring electrodes prepared with the second paste containing 10 wt% of
NiO nanoparticles, baked at 400 o C, and soaked for 3 h showed the highest efficiencies for both
types of PDI. The corresponding values of 0.015 and 0.016 % evolved for the symmetric and
the non-symmetric PDI, respectively.
References
[1] Morandeira; A., et al. "Improved Photon-to-Current Conversion Efficiency with a Nanoporous p-Type NiO
Electrode by the Use of a Sensitizer-Acceptor Dyad". J. Phys. Chem. C 112, 1721-1728 (2008
[2] Le Pleux, L.; et al. "Synthesis, photophysical and photovoltaic investigations of aceptor-functionalized perylene
monoimide dyes for nickel oxide p-type dye-sensitized solar cells". Energy Environ. Sci. 4, 2075-2084 (2011).
© SEFIN 2012