Proceedings of the European Summer School of Photovoltaics 4 – 7 ...

Tab. 2. The roughness parameters of the polyoxadiazoles thin films in the
program carried out XEI’s Park System
Spin speed [rev/min] Max height [nm] R a
[nm] R q
[nm]
1000 33,728 10,634 14,447
2000 46,776 5,276 10,999
3000 43,010 4,773 8,393
Where: Rq – the root-mean-squared roughness. It is the standard deviation
of the height value, Ra – the roughness average, Max height – a maximum
height.
Fig. 6. shows the plot of absorbance on the wavelength of the
polymer DDE-Per-6F (2:1:1). The curves were determined for the
layers deposited at different spin speeds. The largest absorption
coefficient of the polymer obtained with a spin speed 1000 rev/
min and the absorbance reached a value of 1.3 at a wavelength of
about 380 nm. Spin coated thin film obtained with a 2000 rev/min
is characterized by a much lower absorption coefficient equal to
0.8 at a wavelength of 350 nm.
Summary
The spin coating method allows the deposition of the uniform thin
films. The process is dependent primarily on the correct preparation
of the solution. In view of consideration both the results of
surface topography and the absorbance of the best results were
obtained for the thin film deposited at 3000 rev/min. Studies on
the polymers conjugated are interesting because of their possible
application in the structure of polymer solar cells and dye sensitized
solar cells.
Fig. 6. The dependence of absorbance on the wavelength of the polymer
DDE-Per-6F (2:1:1)
References
[1] Drozdov N.: Ogniwa fotowoltaiczne dla energetyki słonecznej.
Wydawnictwo Politechniki Lubelskiej, Lublin 2006.
[2] Torbicz W., D. Pijanowska: Polimery elektroprzewodzące w elektronice
i analityce biochemicznej. Elektronika 2009, nr 6, s. 36–43.
[3] Shirakawa H.: Synthetic Metals. 1995, 69, 3–8.
[4] Gruin I.: Materiały polimerowe. PWN, Warszawa, 2003.
[5] Schulz B., Y. Kaminorz; L. Brehmer: New Aromatic Poly(l,3,4-
oxadiazole)s for Light Emitting Diodes. University Potsdam, Institute
of Solid State Physics Kantstrasse 55, D – 14513 Teltow, Germany.
[6] Poroń A.: Syntetyczne metale. Wiedza i Życie nr 2/2001.
Photovoltaic bulk heterojunctions with interpenetrating
network based on semiconducting polymers
Michał Modzelewski, Ewa Klugmann-Radziemska
Gdańsk University of Technology, Chemical Faculty
Bulk heterojunctions with interpenetrating network architecture
(BHS) is nowadays the most prospective one exploited for organic
electronic devices manufacturing as it enables fabricating
large and flexible areas of light-emitting diodes, transistors and
solar cells. Bulk heterojunction with internal network of percolation
paths is intermixed spatial blend of two physically stable phases
(Fig. 1). One of the phases is composed of electron-donor
compound which is characterized by low ionization potential and
second with high electron affinity acts as an electron-acceptor.
Exceptional position of BHS amongst all architectures of organic
PV devices can be explained primarily by possibility of low-cost
deposition of soluble organic photoactive compounds by means
of novel techniques such as spin-coating, screen printing or doctor
blading on the one side and by achieving internal network within
an exciton diffusion length on the other side.
Until that day the most effective bulk heterojunction based on
semiconducting (conjugated) polymers is structure of Poly(3-hexyltiophene)
(P3HT) acting as electron donor an Phenyl-C 60
-butyric
acid methyl ester as electron acceptor [1] (Fig. 2).
There are different BHJ technologies referred to type of applied
materials. The common part for all of them is solubility of constituent
compounds. As far as BHJs are charge transfer systems one may
divide them into polymer/fullerene derivatives, polymer/polymer,
low-band gap polymers/fullerene derivatives, polymer/inorganic
compound and polymer/oxide. All mentioned may be doped or not.
To find our own place amongst organic photovoltaic we decided to
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apply low-band gap polymer for organic solar cell. The main goal of
following paper was to construct an organic photovoltaic cell in BHJ
architecture based on very low band gap polymer, soluble derivative
of fullerene and organic dopant. To construct a junction which
potentially would be able to harvest solar radiation from the spectrum
of near infrared (Fig. 3) we selected three organic and soluble
compounds with different type of induced conductivity: low-band
gap polymer poly(indenefluorene) (PIF) (Fig. 4a) with low ionization
potential acting as a base electron-donor, fullerene derivative
of phenyl-C 60
-butyric acid methyl ester (PCBM) acting as effective
electron acceptor (Fig. 2b) and 7,7,8,8-tetracyanoquinodimethane
(TCNQ) (Fig. 4b) as additional electron-acceptor of photoinduced
electrons.
Low iron glass
PEDOT:PSS
Light
Donor:acceptor intermixed blend
Indium Tin Oxide
Metal cathode
Fig. 1. Cross-section of organic photovoltaic cell containing blend
as a photoactive layer and composed of PEDOT:PSS on substrate
made from ITO (anode) with metal cathode deposited by vacuum
evaporator
Elektronika 6/2012