Fabrication Process of Organic Solar Cells
Enrique Pérez-Gutiérrez
Oracio Barbosa, J. L: Maldonado, M. A. Meneses Nava,
M. Rodríguez, G. Ramos, J. Gaspar Armenta, Eric Rosas
1
Outline:
 Organic materials for OPV, a chemical point of view
Organic conjugation (organic semiconductor)
 Charge transport
 Fabrication processes
 Organic films deposition
 Electrodes deposition
 Recent advances by GPOM-CIO
2
ORGANIC CONJUGATION
3
Organic materials for OPV
Inorganic semiconductor
Banda
de
conducción
Banda de
valencia
4
Organic materials for OPV
Organic conjugation
5
Organic materials for OPV
Organic conjugation
•Amorphous material
• conjugation length
6
Organic materials for OPV
Organic conjugation & absorption wavelength
7
Organic materials for OPV
Functional groups
X
X
N
2
1
NH2
N
CH3
N
H
N
CH3
N
N
CH3
X= a
b
H
H3C
c
d
e
f
8
CH3
Organic materials for OPV
Functional groups
N: 1S22S22P3
9
Organic materials for OPV
Functional groups
CN
CN
CN
NC
CN
NC
NC
NC
LUMO= -3.22 eV
LUMO= -3.28 eV
ε
Intensity (a.u.)
LUMO= -3.16 eV
wavelength
10
Organic materials for OPV
ε
Functional groups: Donor-Acceptor structure
11
Organic materials for OPV
CHARGE TRANSPORT
12
Organic materials for OPV
Charge transport
• Charge in Organic
materials forms
“Polarons”
“The fundamental mechanisms of electron and hole transport
in amorphous organic solids, however, are not well understood”
13
Organic materials for OPV
Charge transport
“The main mechanics for charge transport in organic semiconductors is Hopping.
The charges brings between neighbors molecules due to net vibrations activated by
temperature or electric field (Poole-Frenkel model)”
14
FABRICATION PROCESS
15
Fabrication process
ETL: polymer PFN, LiF, TiOx, ZnO (≈ 10 nm)
HTL: polymer PEDOT:PSS (≈ 50 nm), MoO3 (≈ 10 nm)
Cathode: Al, Ca, Ag, Wood´s Metal, Field´s Metal
16
Fabrication process
Deposition of organic films:
Evaporation for low molecular weight compounds
Important parameters:
* Evaporation rate
* Thickness control
* Morphology
17
Fabrication process
Polymers
Important parameters:
* Thickness: Viscosity,
speed, vapor solvent
pressure.
Solvent effect
* Thickness
* Morphology
* Miscibility
18
Fabrication process
Polymers large area
Roll to roll
Doctor blade
19
Fabrication process
Cleaning process: Ultrasonic bath with
* Soap and deionized water (remove grease)
* Alcohol (ethanol or isopropanol)
* Acetone (remove organic impurities)
Oxygen plasma treatment:
Indium thin oxide
20
Fabrication process
Cleaning
Activation
21
Fabrication process
ITO surface morphology
Average roughness: 4.99 nm
ITO electro polished surface
Average roughness: 2.88 nm
22
Fabrication process
PEDOT:PSS (50 nm)
ITO/Glass
4.8 eV
PEDOT:PSS
ITO
HTL: polymer (PEDOT:PSS), MoO3
* Soluble in water
* Deposited by spin-coating
* HOMO: 5 eV
* Conductivity: 1 s/cm
5.0 eV
23
Fabrication process
Important parameters:
* Miscibility and ratio between
polymer and fullerene:
P3HT:C71 (1:0.8)
PTB6:C71 (1:1.5)
MEH-PPV:C71 (1:3)
Active layer (80 nm)
PEDOT:PSS (50 nm)
ITO/Glass
Solvent and additive
P3HT
PTB7
24
Fabrication process
ETL: polymer PFN, ZnO, TiOx
TiOx
ETL
Active layer (80 nm)
PEDOT:PSS (50 nm)
ITO/Glass
4.4 eV
8.1 eV
Al
4.2 eV
* Soluble in non organic solvent
* Deposited by spin-coating
* High electron movility
* LUMO or Conduction band near to
cathode work function
Cathode
* Low work function: Ca, Al, ag
deposited bye evaporation
25
Fabrication process
OLED HOME-MADE PROCESS
26
Recent advances by GPOM-CIO
27
Recent advances by GPOM-CIO
PCBM C61, C71
MEH-PPV
Cahtode: Wood´s metal
Field´s metal
28
Fabrication process
- Wood´s Metal:
(25% Pb, 50% Bi, /12.5 Cd,
12.5% Sn), M.P. 75°C
- Field´s Metal
(32.5% Bi, 51% In, 16.5% Sn),
M.P. 62 °C
29
Recent advances by GPOM-CIO
MEH-PPV
PCBM C61, C71
J.-F. Salinas et al. Sol. Ener. Mater. & Sol. Cells 95 (2011) 595–601 30
Recent advances by GPOM-CIO
PCBM C61, C71
P3HT
C. Salto et al. Synthetic Metals 161 (2011) 2412– 2416
31
Recent advances by GPOM-CIO
Metals used as cathode in
OPVs:
Wood´s metal
Field´s metal
Indium-galium
Aluminio
J.C. Nolasco et al. Appl. Phys. Lett. 104 (2014) 043308
32
Recent advances by GPOM-CIO
E. Pérez et al. Optical Mat. Aceptado
33
Recent advances by GPOM-CIO
TiOx (sol-gel)
η
Voc
Jsc
(mV)
(mA/cm2)
None
809
4.35
0.31
1.12
MEH-PPV:PC71BM (1:3)
TiOx
837
4.50
0.41
1.55
MEH-PPV:PC71BM (1:3)
TiOx:PC71BMa
846
5.77
0.41
2.66
P3HT:PC71BM (1:0.8)
None
507
7.76
0.39
1.48
P3HT:PC71BM (1:0.8)
TiOx
532
7.86
0.51
2.12
P3HT:PC71BM (1:0.8)
TiOx:PC71BMa
555
7.77
0.47
2.02
Components (weight ratio)
ETL
MEH-PPV:PC71BM (1:3)
FF
(%)
E. Pérez et al. Optical Mat. Aceptado
34
Recent advances by GPOM-CIO
Higher values
obtained with OPV
based on MEH-PPV
o P3HT and PCBM
Voc = 830 mV
Jsc = 10.8 mA/cm2
FF = 0.6
ƞ = 2.66 %
35
Recent advances by GPOM-CIO
36
Agradecimientos
37
Recent advances by GPOM-CIO
Glove box and evaporation system (POMCIO)
38
Recent advances by GPOM-CIO
PTB7
Field´s metal or Al
PFN
PFN o LiF
PTB7:PC71BM (80 nm)
PEDOT:PSS (50 nm)
ITO/Glass
Z. He, et al., Nature Photon. 2012, 6, 591–595
Z. He, et al., Adv. Mater. 2011, 23, 4636–4643
39
Recent advances by GPOM-CIO
ITO/PEDOT/PTB7-PC71BM(Chlorobencene)/PFN/Field´s metal
Jonathan Pérez (undergraduate student CIO)
ITO/PEDOT/PTB7-PC71BM(Chlorobencene+DIO)/PFN/Field´s metal
Álvaro Romero (Ph. D. student CIO)
40
Recent advances by GPOM-CIO
ITO/PEDOT/PTB7:PC71BM(CB+DIO)/LiF/Al
2
J (mA/cm )
0
-5
Voc=736 mV
2
Jsc=14.8 mA/cm
FF=0.46
=5.06
PTB7
-10
ETL: LiF
Cathode: Al
Deposited by evaporation
-15
0.0
0.2
0.4
V (Volts)
0.6
0.8
41
Recent advances by GPOM-CIO
ITO/PEDOT/PTB7:C71/LiF/Al
2
J (mA/cm )
0
-5
Tower a high efficiency
(7 %)
Voc=736 mV
2
Jsc=14.8 mA/cm
FF=0.46
=5.06

Jsc = 
Voc =
-10
-15
0.0
Reproducibility
FF = challenge
0.2
0.4
0.6
0.8
V (Volts)
42
Recent advances by GPOM-CIO
How to improve the Fill Factor
- Active layer/metal interface
- Thickness and stiffness of ETL
- Al evaporation rate
G. Bag et al. Appl. Phys. Lett. 92 (2008) 093301
43
summary
* Organic photovoltaic devices implies a low cost and high volume
production
* High efficiency will be achieved in next years
* Mechanical properties for OPVs make them suitables for new
and innovative applications
* In Mexico GPOM-CIO has done important contributions in the
field of OPVs
44
Acknowledge
CONACYT-SENER (grant 153094 )
CONACYT-CIO for postdoctoral fellowship
Thanks for your attention