The document discusses advancements in mesoscopic solar cells, focusing on dye-sensitized solar cells (DSSCs) and perovskite solar cells, highlighting key techniques, materials, and efficiencies achieved. It covers various aspects including efficiency improvements, challenges in industrialization, and innovative applications, while also noting the importance of stability and alternative materials for redox systems. The findings indicate a significant move towards high-performance photovoltaic solutions, particularly with perovskite technologies approaching the efficiencies of traditional materials like GaAs.

1. B-MRS 2016, Campinas, September 29, 2016
The Versatility of Mesoscopic Solar Cells
Anders Hagfeldt
Laboratory of Photomolecular Sciences (LSPM)
Dyenamo AB
www.dyenamo.se
Materials, research equipment, consultancy, etc, for solar cells and solar fuels.

2. Welcome to Lausanne!
• Dye-sensitized solar cells
• Minimizing internal potential losses
• Cu-complex redox species
• Perovskite solar cells
• Mixed compositions
• Planar devices > 20%
• The quadrupole
• Stable perovskite solar cells
• Towards GaAs ?

3. The Solar Cell Kit

4. Solar Cells from the Kitchen
White
pigment
TiO2
Dye
Blueberry,
Tea, Wine ...
Cathode:
Grafite
Electrolyte:
Iodide/tri-iodide
Electrical
contatcs
The solar cell
drives a simple
LCD display

5. Dye-Sensitization
Colour Photography, Erythrosin dye on
Ag-halides. J. Moser, Monatsh. Chem.
8 (1887) 373
Mechanism of dye-sensitization. Rose bengal
on ZnO. H. Gerischer and H. Tributsch,
Ber. Bunsenges. Phys. Chem. 72 (1968) 437.
Gerischer, H.; Michel-Beyerle, M. E.;
Rebentrost, F.; Tributsch, H.
Electrochim. Acta 1968, 13, 1509.

6. The Quantum Leap of DSSC –
a paradigm shift of photovoltaics
Nature, 1991, 353, 7377.
J. Phys. Chem, 1990, 94, 8720.
Olympic Games,
Mexico, 1968
From 8.35 m 8.90 mFrom < 1% 7.1%
Brian O’Regan and Michael Grätzel
HOPV 2012, juanbisquert.wordpress.com
Bob Beamon

7. TiO2
Light
e-e-
E
I- /
I3
-
e
-
DyeTCO
Electrolyte
e
-
hn
e
-
e
-
Dye-sensitized
Solar Cells
DSC Operational Principles

8. Why are the electrons moving in the right direction?
Kinetic model
fs
ns - ms
ns - ms
ms
e-
e-
e- Ru
N
N
N
N
N
N
C
C
S
S
HOOC
HOOC
COOH
COOH
+
+
Excited dye
Semiconductor Dye Electrolyte
e
Charge separation due to the molecular architecture
of the dye/oxide interaction

9. DSC niche applications
Vertical –
Facades
North-West Orientation
Intermittent and Diffuse Light
Design –
Appearance
Indoor
High
Voltage

10. 10
Industrialization of DSC - status
Consumer Electronics - YES
Large-scale electricity production – Breakthroughs needed!
Requires < 0.5$/Wpeak
DSC in buildings – ?
Logitech
Solaronix will build the glass facade for
the new congress building at EPFL

11. The Hunt for the Half Volt –
Limitation with the I-/I3
- redox system
E0’(I3
-/I-) = 0.34 V
E0’(D+/D) = 1.10 V
0.76 V
E0-0 = 1.75 eV
EC = -0.5 V
VOC = 0.74 V
V vs NHE
+
I2
- / I-
A two electron transfer process:
How much of the 0,5 - 0,7V can we
take out of the system?
Need for alternative redox systemsBoschloo, Hagfeldt, Accounts of Chemical
Research, 42 (2009) 1819-1826.

12. In 2010 we introduced the ’marriage’ between a
blocking dye and Co-complex redox systems
D35
Feldt, Gibson, Gabrielsson, Sun, Boschloo, Hagfeldt,
J. Am. Chem. Soc. 2010, 132, 16714.
Efficiency of 7% TiO2 Dye Co-complex

13. Co-sensitization of two organic
dyes; ADEKA-1 and LEG4
Cobalt-phenantroline as redox
couple
Top efficiency: 14.3%

14. How to improve it?
Studies of Driving Force for Regeneration
S. .M. Feldt, G. Wang, G. Boschloo, A. Hagfeldt, J. Phys. Chem. C 2011, 115, 21500
Electron transfer studies show that a driving force of 0.4V is necessary for efficient
regeneration of the oxidized dye in these systems.

15. Cu-complexes as redox couple in liquid
DSC
Copper phenanthroline
complexes Cu(I) and Cu(II)
Organic dye, LEG4
Marina Freitag et al. J. Phys. Chem. C,
DOI: 10.1021/acs.jpcc.6b01658
E0’ Cu(I/II)(dmp)2 = 0.94 V vs SHE
Efficient dye regeneration with a
driving force of only 0.2V!

16. Breakthrough using Cu-complex as hole
transporter material for solid-state DSC
Dried out
Cu-complex layer
Efficiency of 8.2%.
Conventional spiro-OMeTAD
gave 5.6%.
Marina Freitag et al., Energy & Environ. Sci., 2015, 8, 2634-2637

17. Several Concepts Based on DSC, some examples
-
+
Photoanode
Photocathode
Q-dot Solar Cells
Dye-sensitized Solar Fuel
Solid-state DSC
Tandem DSC

18. Tsutomu (Tom ) Miyasaka playing his violin fabricated in
1835 in Torino Italy during the ICES 2014 conference
Dinner in Niseto, Hokkaido, Japan on February 06, 2014.
PSCs evolved from the DSC
The first embodiment of a PSC described by Miyasaka
In his 2009 JACS paper was a mesoscopic dye sensitized
solar cell using ammonium lead halide perovskites
as sensitizer and iodide base liquid electrolyte.

19. Chung, I., Lee, B., He, J., Chang, R. P. H. &
Kanatzidis, M. G. All-solid-state dye-sensitized
solar cells with high efficiency Nature 485,
4478?6?–4?8?9 (2012).
Year 2012 Landmark paper for PSCs
Electron conduction assumed by
CH3NH3PbI3

Hole conduction assumed by PSC
H.S.Kim, C.R.Lee, J.H.Im, K.B. Lee, T. Moehl, A. Marchioro, S.J.Moon, R. R.Humphry Baker,
J.H.Yum, J.E. Moser, M. Grätzel, N.G. Park, Lead Iodide Perovskite Sensitized All-Solid-State
Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%, Sci.Reports 2, 591 2012
Science 2012

20. CH3NH3PbI3:
Ambipolar semiconductor band gap 1.55 eV
Bohr radius of the first exciton: 2 nm
Exciton binding energy 10 -30 meV, exciton dissociation time 1-2 ps
!
Band alignement of pervoskite/TiO2/spiro-MeOTAD heterojunction
solar cells

21. PLETHORA OF PEROVSKITE FILM PREPARATION METHODS
Ex. Two-step technique to form the hybrid perovskite :
 spin coating
 dip coating
 chemical vapour deposition
 spray pyrolysis
J. Burschka et al. Nature, 499, 316-319 (2013)
 atomic layer deposition
 ink-jet printing
 thermal evaporation
 etc, …

22. Several Device Structures and Applications
Planar
Mesoscopic
Inverted
• Lasing
• Light emitting devices
• Tandem solar cells
• Photodetectors
• XRD-detection
• …...

24. EPFL’s most efficient pervoskite solar cells employ
mixtures of
organic cations and iodide /bromide as anion
General composition FA1-xMAxPb(I1-xBrx)
FA =
R1 – R4 = H
formamidinium
MA = methylammonium
X = 0.15 gives optimal results
N. Pellet et al., Mixed-Organic-Cation Perovskite Photovoltaics for Enhanced Solar
-Light Harvesting. Angew. Chem. Int. Ed. 53, 3151-3157 (2014).
N. J. Jeon et al., Compositional engineering of perovskite materials for high-performance
solar cells. Nat. 517, 476-480 (2015).

25. Electroluminescent PSCs with PCE = 20.8 based on tailored mixed
cation perovskites use stochiometric excess of PbI2
Dongqin Bi, Wolfgang Tress, M. Ibrahim Dar, Peng Gao, Jingshan Luo, Clémentine Renevier, Kurt Schenk,
Antonio Abate, Fabrizio Giordano, Juan-Pablo Correa Beana, Jean- David Decoppet, Shaik M. Zakeeruddin,
M.Khaja Nazeeruddin, Michael Grätzel and Anders Hagfeldt
• Single step from a solution containing a
mixture of FAI, PbI2, MABr and PbBr2, solvent
DMF:DMSO (vol. 4:1)
• Mesoporous TiO2 and spiro-MeOTAD
• Molar ratio of PbI2/FAI of 1.05 in the precursor
solution.
• Excess PbI2 content is about 3 weight %.
• Excess of PbI2 suppresses non-radiative charge
carrier recombination.
• External electroluminescence quantum
efficiency 0.5 % at a voltage of 1.5 V
• Science Advances 2, (2016) 340

26. ”During spin-coating we introduce PMMA in a
chlorobenzene/toluene mixture to template crystal formation and
growth of the perovskite. The PMMA serves as a support to induce
nucleation of small perovskite crystals and directs the growth of
these crystals.”DOI: 10.1038/NENERGY.2016.142

27. 0
0.3
mg ml-1
0.6
mg ml-1
1.5
mg ml-1
4.0
mg ml-1
Optimal concentration of
PMMA = 0.6 mg ml-1.
FTIR:
The carbonyl groups in
PMMA form an
intermediate adduct
with PbI2. Retard crystal
growth and improve
crystallinity.
Longer electron lifetimes
with PMMA
At higher concentrations
new particles appear at
grain boundaries (PMMA
particles?).

28. Dongqin Bi
Certified efficiency at Newport,
21.0%, Dec. 2015 (hysteresis-free)
Voc = 1.13 V
Jsc = 23.8 mA/cm2
FF = 0.78
PEC = 21.0 %
Our Certified Champion Cell
Certified world record is 22.1%
(March 2016) by Seok et al.

29. Dr. Xiong Li
2016
Vacuum flash treatment
produces smooth and
shiny perovskite films of
high quality

30. Successful scale-up of a mesoscopic PSC to 1cm2 size
Certified PCE 19.6 %
Stabilized power output for
best cell with PCE of 20.3 %
X. Li, D. Bi, C. Yi, J.-D.Décoppet, J. Luo, S. M.
Zakeeruddin, A. Hagfeldt and M.Grätzel*
Science, 10.1126/science.aaf8060 (2016)

31. Cs additive
Michael Saliba
M. Saliba et al.,
Energy & Environmental Science, 2016, DOI: 10.1039/C5EE03874J

32. 2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted)
What happens if caesium (Cs) is added? (Triple cation mixtures)
32
Disappearance of the yellow phase and PbI2 excess
10 20 30 40 50
x = 15%
x = 10%
x = 5%
Intensity(a.u.)
2 (°)
x = 0%
δ
PbI2
10 20 30 40 50
x = 15%
x = 10%
x = 5%
Intensity(a.u.)
2 (°)
x = 0%
Csx(MA0.17FA0.83)(1-x)Pb(I0.83Br0.17)3 (nominal precursor composition)
written as CsxM

33. 2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted)
Devices cross sectional SEM
33
Cs0M Cs5M
Cs5M
• More monolithically grown crystals (not seen before for MA/FA)
Cs5M
M. Saliba et al., Cesium-containing Triple Cation Perovskite Solar Cells: Improved Stability, Reproducibility
and High Efficiency, Energy & Environmental Science, 2016, DOI: 10.1039/C5EE03874J

34. Triple cation perovskites and stability
Cs+ stabilizes the
power output in full
sunlight over
hundreds of hours
Small initial PCE
decline Is reversible
What happens at higher temperatures?

35. Planar PSC Structures Using ALD SnO2
Dr. Ludmilla
Steier
Dr. Juan-Pablo
Correa-Baena
Flat SnO2 ALD layer works better than flat TiO2
ALD Layer - Band Alignment Engineering
hole transporter
Perovskite
electron transporter
Planar devices!
J.-P. Correa Baena, L. Steier et al. Energy Environ. Sci. DOI: 10.1039/C5EE02608C
Stranks, NNANO (2015)
TiO2 SnO2
X
Perovskite Perovskite
HTL
Au

36. 36

37. 37
New Solution-Processed Method for SnO2
deposition
No need of an ALD as in our previous study, while
achieving similar results
Anaraki, E. H.; Kermanpur, A.; Steier, L.; Domanski, K.; Matsui, T.; Tress, W.; Saliba,
M.; Abate, A.; Gratzel, M.; Hagfeldt, A.; Correa-Baena, J.-P.,
Energy & Environmental Science 2016. DOI: 10.1039/C6EE02390H
-25
-20
SnO2 Perovskite
70℃
180℃
Chemical Bath Deposition
Perovskite: Triple cation protocol

38. 38
Yields High Efficiencies
PCEs = 20.8%
0.0 0.2 0.4 0.6 0.8 1.0 1.2
-25
-20
-15
-10
-5
0
Voltage / V
J/mA×cm-2
SC-CB
0 20 40 60
0
10
20
Time / s
PCE/%
Anaraki, E. H.; Kermanpur, A.; Steier, L.; Domanski, K.; Matsui, T.; Tress, W.; Saliba,
M.; Abate, A.; Gratzel, M.; Hagfeldt, A.; Correa-Baena, J.-P.,
Energy & Environmental Science 2016. DOI: 10.1039/C6EE02390H
Best Voc = 1.21 V at
Eg = 1.62 eV.
Close to thermodynamic
limit of 1.32 V!

39. 2016-09-13, Michael Saliba, Multication perovskites
Device results – New system
M. Saliba, T. Matsui, K. Domanski, J.-Y. Seo, A. Ummadisingu, S. M.
Zakeeruddin, J. P. Correa-Baena, W. R. Tress, A. Abate, A. Hagfeldt,
M. Grätzel
Science I, online, Thursday
Sept. 29

40. 40
Device results
• Highest PCE: 21.6% stabilized
• Voc is 1240mV (band gap: 1.63 eV)
Close to theoretical limit
• Among lowest loss-in-potentials
(for any PV material)
• Perovskites close to GaAs!
• Exceptional electroluminescence
• 4% EQE: almost as high as pLEDs

41. 41
Industrial norms that must be fulfilled for perovskites to go commercial:
• 85C in the dark for 1000h (<10% degradation to pass tests!)
• 60C under full illumination and load for 1000h
Problem:
• Au migration into perovskite
Solutions:
• Cr buffer layer
• Polymeric HTMs can hinder gold migration
But is it stable?
ACS Nano DOI: 10.1021/acs.nano.6b02613

42. Stability tests
Stability: 95% is retained after 500h of continous operation (MPP) at 85 oC and full
illumination
Achilles‘ heel is not perovskite but rather Au migration
• Compounded stress test: 85C, full illumination, MPP for 500h (in N2
atmosphere)
• Polymer as HTM
• Starting efficiency of device: > 17%

43. First 3 months, Ar atmosphere.
Next 3 months under air at 50% R,
In both cases under continuous UV irradiation
Terrace of the Politecnico di Torino
from October to December 2015
Encapsulated Cells
Science II, online, Thursday Sept. 29
Federico Bella*, Gianmarco Griffini, Juan-Pablo
Correa-Baena*, Guido Saracco, Michael Grätzel,
Anders Hagfeldt, Stefano Turri, Claudio Gerbaldi

44. For our best Voc we loose 90 mV with an ERE of 1% (at Jsc injected currents) –
Better than the best Si cells!
Towards GaAs?

45. The EPFL team
Michael
Grätzel
LSPM
Dongqin Bi
Juan Pablo Correa-Baena
Marina Freitag
Somayyeh Gholipour
Elham Halvani Anaraki
Jeannette Kadro Medina
Kazuteru Nonomura
Pan Linfeng
Yasemin Saygili
Nick Vlachopoulos
LPI
Shaik M. Zakeeruddin
Wolfgang Tress
Michael Saliba
Konrad Domanski
Antonio Abate
Xiong Li
Chenyi Yi
….