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

0,03
0,02
10
Current density (mA/cm 2 )
0,01
0,00
-0,01
-0,02
-0,03
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
Current density (mA/cm 2 )
1
0,1
0,01
1E-3
PIF:PCBM:TCNQ
P3HT:PCBM (1:0.8)
1E-4
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
Fig. 10. Left: Current-voltage characteristics of loaded junctions of PIF:PCBM:TCNQ (2:2:1), Right: absolute value of current density against
generated voltage for two junctions created in second part of experiment: PIF:PCBM:TCNQ (2:2:1) and P3HT:PCBM (1:1), depicted for comparison
purposes
Tabl. Performance of solar cells created in both steps of experiment (↑ – highest value, ↓ – lowest value, i) – improvement)
Active blend layer (weight ratio)
PIF:PCBM (1:1) PIF:PCBM (2:1) P3HT:PCBM (1:1) PIF:PCBM:TCNQ (2:2:1) P3HT:PCBM (1:0.8)
Concentration 10:10 mg 10:5 mg 10:10 mg 10:10:5 mg 10:8 mg
Solvent cb cb odcb cb odcb
Jsc, max [µA/cm2 ] 15.1 11↓ 5496 21↑ i) 4372
J [µA/cm 2 ] 13.7 10.5 19.5
sc, ave
V oc, max
[V] 0.496↑ 0.431 0.397 0.299↓ 0.625
V oc, ave
[V] 0.472 0.389 0.286
FF max
[%] 29.5 32↑ 52.7 26.6↓ 66.7
FF ave
[%] 29.2 29.8 26.45
PCE max
[%] 0.00215↑ 0.00125↓ 1.16 0.00156 i) 1.69
PCE ave
[%] 0.00189↑ 0.00113↓ 0.00147 i)
EQE max
[%] 0.2↓ 0.2↓ 41.1 0.56↑ i) 36.6
I heat
(A) 40-100 60-80
v growth
[Ĺ/sec] 5-15 7
d [nm] 45 (aluminum) 95 (ytterbium)
Where: J sc, max
, J sc,ave
– maximum and average short circuit current density, V oc, max
, V oc, ave
– maximum and average open circuit voltage, FF max
, FF ave
– maximum
and average fill factor, PCE max
, PCE ave
– maximum and average power conversion efficiency, I heat
– intensity of evaporator’s current, v growth
– speed of cathode
material deposition, d – thickness of cathode, cb – chlorobenzene, odcb – o-dichlorobenzene.
Summary
Poly(indenefluorene) belongs to the exotic and rare group of
synthetic, photoactive, macromolecular compounds which may
replace crystalline silicon in electronics in the future. Although the
attempt of performance improvement it is highly probable that PIF
itself is characterized by low exciton diffusion length and therefore
(apart from PCBM and TCNQ) application of other electronacceptor
in blends with that polymer may be pointless. There is
a particular need of application other conjugated polymers with
optimized band gap around 1.5 eV. Polymers with lower values
of band gap may not deliver satisfying voltages even though they
have well absorption properties. The main obstacle in commercial
applications of low-band gap polymer based devices is that they
have low values of operating currents and external quantum efficiencies.
Few available examples of photovoltaic devices based
of that kind of polymers manufactured in [3, 4] have EQEs less
than 0.01%. New bulks based on other macromolecular chromophores
are needed as presented devices based on PIF may be
used only as a photonic detector of radiation.
References
[1] Koster L. J. A., V. D. Mihailetchi, P. W. M. Blom: Ultimate efficiency
of polymer/fullerene bulk heterojunction solar cells”, Appl. Phys. Lett.
88, 093511 (2006).
[2] Reisch H., Wiesler U., Scherf U., Tuytuylkov N.: Poly(indenofluorene)
(PIF), a Novel Low Band Gap Polyhydrocarbon, Macromolecules, 29
(1996).
[3] Bundgaard E., Krebs F.C.: Low band gap polymers for organic photovoltaics,
Solar Energy Materials and Solar Cells, 91 (2007).
[4] Petritsch K.: Organic Solar Cell Architectures, PhD Thesis, Cambridge,
Graz (2000).
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