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

PIF:PCBM (1:1)
PIF:PCBM (2:1)
Current density (mA/cm 2 )
0,04
0,02
0,00
Current density (mA/cm 2 )
0,04
0,02
0,00
-0,02
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
-0,02
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
Fig. 7. Current-voltage characteristics of loaded junctions of PIF:PCBM (1:1) (left) and PIF:PCBM (2:1) (right)
Current density |J| (mA/cm 2 )
10
1
0,1
0,01
1E-3
P3HT:PCBM (1:1)
PIF:PCBM (2:1)
PIF:PCBM (1:1)
1E-4
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
Fig. 8. Absolute value of current density against generated voltage
for three junctions created in first part of experiment: PIF:PCBM
(1:1), PIF:PCBM (2:1) and P3HT:PCBM (1:1), depicted for comparison
purposes
Results
According to achieved characteristics we read out or calculated
typical parameters which describe the performance of cells. The
nominal parameters of solar cells manufactured in two stages
were presented in Table.
To define the base improvement we created two bulk heterojunctions
i.e. PIF:PCBM (1:1) and PIF:PCBM (2:1). It turned
out that increased amount of PIF in blend deteriorates the performance
of the cell because of insufficient amount of electronacceptor
compound. Taking that factors into account we came
to a conclusion that there is a particular need to apply additional
compound with negative character of conductivity such as TCNQ.
Photoinduced current density/intensity is supposed to be consider
as the most crucial parameter of all solar cells. Insertion of
TCNQ to the polymer/fullerene matrix produces the short circuit
current improvement. Although the degree of that improvement is
rather poor we can conclude that TCNQ increases the efficiency
of charge transfer between constituent phases and causes significant
extending of absorption spectrum up to 900 nm. Despite
the current growth process it is not possible that TCQN improve
the conductivity of percolation paths. External quantum and power
conversion efficiencies growth for PIF:PCBM:TCNQ (2:2:1)
are mainly due to the extended absorption spectrum but deterioration
of open circuit voltage is a result of application ytterbium
as a cathode which has lower work function than aluminum.
10
P3HT:PCBM
PIF:PCBM:TCNQ
1
0
P3HT:PCBM
EQE (%)
1
0,1
0,01
Current density (mA/cm 2 )
-1
-2
-3
-4
1E-3
400 500 600 700 800 900
Wavelength (nm)
-5
-0,2 0,0 0,2 0,4 0,6 0,8 1,0
Voltage (V)
Fig. 9. Left: Absorption spectra of junctions in visible and near infrared part of spectrum: PIF:PCBM:TCNQ (2:2:1) and for comparison purposes
P3HT:PCBM (1:0.8), Right: Current-voltage characteristic of loaded junction of P3HT:PCBM (1:0.8)
124
Elektronika 6/2012