Loss mechanisms in Polymer-Fullerene Solar Cells
-
Upload
disorderedmatter -
Category
Education
-
view
960 -
download
2
description
Transcript of Loss mechanisms in Polymer-Fullerene Solar Cells
![Page 1: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/1.jpg)
Loss mechanisms in Polymer-Fullerene Solar CellsCarsten DeibelJulius-Maximilians-University of Würzburg
223rd ECS meeting, Toronto15th May [email protected]
![Page 2: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/2.jpg)
How Do Organic Solar Cells Work?
2
Step 1: Light Absorption ➟ Exciton Generation in Polymer
Fulle
rene
Aluminium Cathode
Transparent Anode
Polymer
Voltage
Current
![Page 3: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/3.jpg)
How Do Organic Solar Cells Work?
3
Step 2: Exciton Diffusion➟ to Acceptor Interface
Fulle
rene
Aluminium Cathode
Transparent Anode
Polymer
Voltage
Current
singlet losses
![Page 4: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/4.jpg)
Step 3: Exciton Dissociation ➟ Polaron Pair Generation
How Do Organic Solar Cells Work?
4
Fulle
rene
Aluminium Cathode
Transparent Anode
Polymer
charge transfer: very fast and very efficient
Voltage
Current
singlet losses
![Page 5: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/5.jpg)
How Do Organic Solar Cells Work?
5
Step 4: Polaron Pair Dissociation➟ Free Electron–Hole Pairs!
Fulle
rene
Aluminium Cathode
Transparent Anode
Polymer
Voltage
Current
singlet lossesgeminate losses
![Page 6: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/6.jpg)
How Do Organic Solar Cells Work?
6
Step 5: Charge Transport ➟ Photocurrent
Fulle
rene
Aluminium Cathode
Transparent Anode
Polymer
Voltage
Current
singlet lossesgeminate losses
nongeminate losses
![Page 7: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/7.jpg)
for instance, PTB7:PC70BM 1:1.5
What are we looking at?
7glass
PEDOT
V
additive DIO
![Page 8: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/8.jpg)
for instance, PTB7:PC70BM 1:1.5
What are we looking at?
7
300
200
100
0
-100
curre
nt d
ensi
ty [
A/m
2 ]
0.80.60.40.20.0
voltage [V]
dark 1 sunw/o add with add
PCE [%] FF [%]
w/o add 3.8 51
with add 7.1 69glass
PEDOT
V
![Page 9: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/9.jpg)
PTB7:PC70BM 1:1.5 Morphology
8
phas
ehe
ight
w/o additive, 3.8%
Alex Förtig
nm
nm
![Page 10: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/10.jpg)
with additive, 7.1%
PTB7:PC70BM 1:1.5 Morphology
8
phas
ehe
ight
w/o additive, 3.8%
Alex Förtig
nm
nm
![Page 11: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/11.jpg)
Which processes are limiting the
performance of these organic solar cells?
![Page 12: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/12.jpg)
Outline
10
![Page 13: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/13.jpg)
Outline
10
conclusions
implications on organicsolar cell performance
nongeminate recombination
with additive
geminate recombination
without additive
![Page 14: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/14.jpg)
Outline
10
conclusions
implications on organicsolar cell performance
nongeminate recombination
with additive
geminate recombination
without additive
![Page 15: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/15.jpg)
j(V ) = e
Z(G�R) dx
⇡ j
gen
� j
loss
(V )
jgen ⇡ jsc
Current–Voltage Reconstruction ...
11
From the continuity equation:
Voltage
Current
jloss
(V ) / n(V )
⌧(n)
![Page 16: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/16.jpg)
12
n(V) by charge extraction5.2. Impact of Solvent Additive on PTB7:PC71BM Solar Cells 65
2
4
1021
2
4
1022
0.80.60.40.20.0
voltage [V]
1021
2
4
1022
2
4
char
ge c
arrie
r den
sity
[m-3
]
with add
w/o add
0.03 sun
1 sun
Figure 5.12: Voltage dependent charge carrier density n(V ) from charge ex-traction experiments for PTB7:PC71BM devices with and without additive atthree different light intensities.
range were performed, in analogy to the measurements at V
oc
described onpage 63. All voltages were corrected for the series resistance R
s
by calculatingV = V
app
� R
s
I. From the ohmic range of the dark j/V curve, the valuesR
s
⇡ 84 ⌦ for the device with additive and R
s
= 105 ⌦ for the one withoutadditive were derived. The voltage dependent charge carrier density for bothdevices is shown in Fig. 5.12 for three different light intensities.
The n(V ) relation and the dependence of ⌧ on n found under V
oc
conditions(Fig. 5.10) is used to calculate the charge carrier density dependent recom-bination rate R(n(V )) for the respective applied voltage by Eq. (2.4). Thisdata was fed into Eq. (4.14), which allowed to determine the nongeminaterecombination current j
loss
(n(V )).As the photogeneration of the sample with additive was voltage indepen-
dent, as shown in Fig. 5.11, the respective generation current j
gen
was assumedto be constant and set equal to the short circuit current density,
j
gen
⇡ j
sc
, (5.5)
similar to the case of P3HT:PC61BM (Sec. 5.1) and the approach in Ref. [58,94].
Instead, for the solar cell spin coated from pure CB solution, the voltagedependent polaron pair dissociation PP(V ) derived by TDCF is substantial
Alex Förtig
jloss
(V ) / n(V )
⌧(n)Nongem. Loss Current
![Page 17: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/17.jpg)
τ(n) by transient photovoltage
12
n(V) by charge extraction5.2. Impact of Solvent Additive on PTB7:PC71BM Solar Cells 65
2
4
1021
2
4
1022
0.80.60.40.20.0
voltage [V]
1021
2
4
1022
2
4
char
ge c
arrie
r den
sity
[m-3
]
with add
w/o add
0.03 sun
1 sun
Figure 5.12: Voltage dependent charge carrier density n(V ) from charge ex-traction experiments for PTB7:PC71BM devices with and without additive atthree different light intensities.
range were performed, in analogy to the measurements at V
oc
described onpage 63. All voltages were corrected for the series resistance R
s
by calculatingV = V
app
� R
s
I. From the ohmic range of the dark j/V curve, the valuesR
s
⇡ 84 ⌦ for the device with additive and R
s
= 105 ⌦ for the one withoutadditive were derived. The voltage dependent charge carrier density for bothdevices is shown in Fig. 5.12 for three different light intensities.
The n(V ) relation and the dependence of ⌧ on n found under V
oc
conditions(Fig. 5.10) is used to calculate the charge carrier density dependent recom-bination rate R(n(V )) for the respective applied voltage by Eq. (2.4). Thisdata was fed into Eq. (4.14), which allowed to determine the nongeminaterecombination current j
loss
(n(V )).As the photogeneration of the sample with additive was voltage indepen-
dent, as shown in Fig. 5.11, the respective generation current j
gen
was assumedto be constant and set equal to the short circuit current density,
j
gen
⇡ j
sc
, (5.5)
similar to the case of P3HT:PC61BM (Sec. 5.1) and the approach in Ref. [58,94].
Instead, for the solar cell spin coated from pure CB solution, the voltagedependent polaron pair dissociation PP(V ) derived by TDCF is substantial
with add.
4
68
10
2
4
68
100
lifet
ime
[µs]
3 4 5 6 7 8 9
1022
2
charge carrier density [m-3
]
1sun
1sun
w/out add.
Alex Förtig
jloss
(V ) / n(V )
⌧(n)Nongem. Loss Current
![Page 18: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/18.jpg)
reconstruction works well
... with Additive
Origin of nongeminate recombination?
13
-150
-100
-50
0
50C
urre
nt D
ensi
ty [A
/m2 ]
0.60.40.20.0
Voltage [V]
meas. PL reconstr. 1 sun 0.32 sun 0.03 sun
Alex Förtig
![Page 19: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/19.jpg)
LUMO
HOMO
(1)
(2)
(1)
expected in nongeminate loss in low mobility materials
Langevin Recombination
(1) finding of charge carriers → mobility μ(2) recombination event (faster than (1))
14
R(n) / µ(n)n2}
![Page 20: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/20.jpg)
Expected:
Back to PTB7: Expected vs Observed
15Adv. Funct. Mater. 2, 1483 (2012)
3
4
5
6789
10-20
2
3
µ [A
m]
4 6 81021
2 4 6 81022
2 4 6 81023
charge carrier density [m-3]
10-18
2
3
4
5
678910-17
k [m3s
-1]
PTB7:PC!with additive
71BM
~
T=300 K
![Page 21: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/21.jpg)
Expected:
Back to PTB7: Expected vs Observed
15Adv. Funct. Mater. 2, 1483 (2012)
3
4
5
6789
10-20
2
3
µ [A
m]
4 6 81021
2 4 6 81022
2 4 6 81023
charge carrier density [m-3]
10-18
2
3
4
5
678910-17
k [m3s
-1]
PTB7:PC!with additive
71BM
~
T=300 K
![Page 22: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/22.jpg)
Expected:
Back to PTB7: Expected vs Observed
15Adv. Funct. Mater. 2, 1483 (2012)
3
4
5
6789
10-20
2
3
µ [A
m]
4 6 81021
2 4 6 81022
2 4 6 81023
charge carrier density [m-3]
10-18
2
3
4
5
678910-17
k [m3s
-1]
PTB7:PC!with additive
71BM
~
T=300 K
![Page 23: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/23.jpg)
6/
Expected:
Back to PTB7: Expected vs Observed
15Adv. Funct. Mater. 2, 1483 (2012)
3
4
5
6789
10-20
2
3
µ [A
m]
4 6 81021
2 4 6 81022
2 4 6 81023
charge carrier density [m-3]
10-18
2
3
4
5
678910-17
k [m3s
-1]
PTB7:PC!with additive
71BM
~
T=300 K
![Page 24: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/24.jpg)
Trap Tail States by Thermally Stimulated Currents
Trapping is Important
Trap density = Lower Limit
Shape roughly exponential, energy tail ~90 meV
16Julia Rauh
1021
2
3
4
5
6789
1022
trap
dens
ity [m
-3]
0.300.250.200.150.100.050.00
Energy [eV]
PTB7:PC70BMwith DIO
![Page 25: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/25.jpg)
Transient Absorption
Nongeminate Decay Dynamics
17
46810-5
2
46810-4
2
468
ΔO
D [a
.U]
10-7 10-6 10-5 10-4 10-3
Time [s]
PTB7:PC71BMwith additive
300K 150K
4.5K
Clemens Grünewald, Julia Kern
![Page 26: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/26.jpg)
Transient Absorption
Nongeminate Decay Dynamics
17
46810-5
2
46810-4
2
468
ΔO
D [a
.U]
10-7 10-6 10-5 10-4 10-3
Time [s]
PTB7:PC71BMwith additive
300K 150K
4.5K
fast free–free (Langevin type) recombination
Clemens Grünewald, Julia Kern
![Page 27: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/27.jpg)
Transient Absorption
Nongeminate Decay Dynamics
17
46810-5
2
46810-4
2
468
ΔO
D [a
.U]
10-7 10-6 10-5 10-4 10-3
Time [s]
PTB7:PC71BMwith additive
300K 150K
4.5K
fast free–free (Langevin type) recombination
slow free–trappedrecombination
Clemens Grünewald, Julia Kern
![Page 28: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/28.jpg)
Outline
18
conclusions
implications on organicsolar cell performance
nongeminate recombination
with additive
geminate recombination
without additive
![Page 29: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/29.jpg)
PTB7:PC70BM 1:1.5 w/o additive
I–V Reconstruction
Why?
19
reconstruction incomplete
j(V ) = jsc
� jloss
(n(V ))
-50
-40
-30
-20
-10
0
10
Cur
rent
Den
sity
[A/m
2 ]
0.80.60.40.2
Voltage [V]
meas. PL reconstr. 0.56 sun 0.32 sun 0.18 sun 0.03 sun
![Page 30: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/30.jpg)
PTB7:PC70BM 1:1.5 w/o additive
I–V Reconstruction
Why?
19
reconstruction incomplete
j(V ) = jsc
� jloss
(n(V ))
-50
-40
-30
-20
-10
0
10
Cur
rent
Den
sity
[A/m
2 ]
0.80.60.40.2
Voltage [V]
meas. PL reconstr. 0.56 sun 0.32 sun 0.18 sun 0.03 sun
1.0
0.8
0.6
0.4
0.2
mea
sure
d/re
cons
truct
ed
0.80.60.40.2
Voltage [V]
ratio PL Voc 0.03 sun 0.18 sun 0.32 sun 0.56 sun 1 sun
First try:
![Page 31: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/31.jpg)
Time Delayed Collection Field → P(V)
Main Reason: Photogeneration
w/out additive: voltagedependent photogeneration
20Alex Förtig
5
6
7
8
9
1
Qto
t / Q
(-5
V)
-5 -4 -3 -2 -1 0prebias voltage [V]
w/o add data fit
with add data origin unclear
![Page 32: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/32.jpg)
j(V ) = e
Z(G�R) dx
⇡ j
gen
� j
loss
(V )
jgen ⇡ jsc
Current–Voltage Reconstruction ...
21
From the continuity equation:
Voltage
Current
jloss
(V ) / n(V )
⌧(n)
![Page 33: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/33.jpg)
j(V ) = e
Z(G�R) dx
⇡ j
gen
(V )� j
loss
(V )
Current–Voltage Reconstruction ...
22
From the continuity equation:
jloss
(V ) / n(V )
⌧(n)
Voltage
Current
jgen(V ) ⇡ jsc · P (V )
![Page 34: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/34.jpg)
Time Delayed Collection Field
Reconstruction incl. Geminate Loss
23
5
6
7
8
9
1
Qto
t / Q
(-5
V)
-5 -4 -3 -2 -1 0prebias voltage [V]
w/o add data fit
with add data
![Page 35: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/35.jpg)
Time Delayed Collection Field
Reconstruction incl. Geminate Loss
23
5
6
7
8
9
1
Qto
t / Q
(-5
V)
-5 -4 -3 -2 -1 0prebias voltage [V]
w/o add data fit
with add data
-80
-60
-40
-20
0
curr
ent d
ensi
ty [A
/m2 ]
0.80.60.40.2
voltage [V]
0.18 sun
1 sun
w/o Add
measurement reconstruction
j (V)gen
![Page 36: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/36.jpg)
2
4
1021
2
4
1022
0.80.60.40.20.0
voltage [V]
1021
2
4
1022
2
4
char
ge c
arrie
r den
sity
[m-3
]
with add
w/o add
0.03 sun
1 sun
What if...
reverse reconstruction: n(V) from I(V)
24Alex Förtig
incomplete extraction
![Page 37: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/37.jpg)
„Nanomorphology“ by PL
25Björn Gieseking
1.0
0.8
0.6
0.4
0.2
0.0
Pho
tolu
min
esce
nce
(nor
m.)
2.01.81.61.41.2
Energy / eV
1.0
0.5
0.0
1100 1000 900 800 750 700 650
Wavelength / nm
w/o add. 3 % DIO
PTB7 PC71BM
![Page 38: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/38.jpg)
„Nanomorphology“ by PL
additive: relative decrease of fullerene PL→ smaller fullerene domains
25Björn Gieseking
1.0
0.8
0.6
0.4
0.2
0.0
Pho
tolu
min
esce
nce
(nor
m.)
2.01.81.61.41.2
Energy / eV
1.0
0.5
0.0
1100 1000 900 800 750 700 650
Wavelength / nm
w/o add. 3 % DIO
PTB7 PC71BM
![Page 39: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/39.jpg)
...on fullerene islands
Scenario: Spatial Trapping...
without additive
26
Fulle
rene
Polymer
Aluminium Cathode
Transparent Anode
Fulle
rene
Polymer
Aluminium Cathode
Transparent Anode
with additive
![Page 40: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/40.jpg)
Conclusions
27
with additive, 7.1% w/o additive, 3.8%
![Page 41: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/41.jpg)
Conclusions
27
with additive, 7.1% w/o additive, 3.8%
nongeminate recombination
free carrier and trap assisted recombination
![Page 42: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/42.jpg)
Conclusions
27
with additive, 7.1% w/o additive, 3.8%
nongeminate recombination
free carrier and trap assisted recombination
geminate & nongeminate
field dependent photogeneration
spatial trappingon fullerene
![Page 43: Loss mechanisms in Polymer-Fullerene Solar Cells](https://reader034.fdocuments.in/reader034/viewer/2022042607/55657445d8b42a95028b49ae/html5/thumbnails/43.jpg)
Thanks to Prof. Dyakonov and Würzburg group!
Thank you! [email protected]
Bayerische Akademie der Wissenschaften
EU, DBU, Elite network Bavaria