B-MRS 2016, Campinas, September 29, 2016

The Versatility of Mesoscopic Solar Cells

Anders HagfeldtLaboratory of Photomolecular Sciences (LSPM)

Dyenamo ABwww.dyenamo.seMaterials, research equipment, consultancy, etc, for solar cells and solar fuels.

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 ?

The Solar Cell Kit

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

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.

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 m

From < 1%

7.1%

Brian O’Regan and Michael GrätzelHOPV 2012, juanbisquert.wordpress.com

Bob Beamon

TiO2

Light

e-e-

E

I- / I3-

e-

DyeTCOElectrolyte

e-

hn

e-

e-

Dye-sensitized Solar Cells

DSC Operational Principles

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

NC

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

DSC niche applications

Vertical – Facades

North-West Orientation

Intermittent and Diffuse Light

Design – Appearance

Indoor

HighVoltage

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

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 wetake out of the system?

Need for alternative redox systemsBoschloo, Hagfeldt, Accounts of Chemical Research, 42 (2009) 1819-1826.

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

Co-sensitization of two organic dyes; ADEKA-1 and LEG4

Cobalt-phenantroline as redox couple

Top efficiency: 14.3%

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 efficientregeneration of the oxidized dye in these systems.

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 SHEEfficient dye regeneration with a driving force of only 0.2V!

Breakthrough using Cu-complex as hole transporter material for solid-state DSC

Dried outCu-complex layer

Efficiency of 8.2%. Conventional spiro-OMeTAD gave 5.6%.

Marina Freitag et al., Energy & Environ. Sci., 2015, 8, 2634-2637

Several Concepts Based on DSC, some examples

-

+

Photoanode

Photocathode

Q-dot Solar CellsDye-sensitized Solar Fuel

Solid-state DSC

Tandem DSC

Tsutomu (Tom ) Miyasaka playing his violin fabricated in1835 in Torino Italy during the ICES 2014 conference Dinner in Niseto, Hokkaido, Japan on February 06, 2014.

PSCs evolved from the DSCThe first embodiment of a PSC described by Miyasaka In his 2009 JACS paper was a mesoscopic dye sensitized solar cell using ammonium lead halide perovskitesas sensitizer and iodide base liquid electrolyte.

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

CH3NH3PbI3: Ambipolar semiconductor band gap 1.55 eV Bohr radius of the first exciton: 2 nmExciton binding energy 10 -30 meV, exciton dissociation time 1-2 ps

Band alignement of pervoskite/TiO2/spiro-MeOTAD heterojunction solar cells

PLETHORA OF PEROVSKITE FILM PREPARATION METHODSEx. 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, …

Several Device Structures and Applications

Planar

Mesoscopic

Inverted

• Lasing• Light emitting devices• Tandem solar cells

• Photodetectors• XRD-detection• …...

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 = methylammoniumX = 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).

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

”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

0

0.3 mg ml-1

0.6 mg ml-1

1.5 mg ml-1

4.0mg 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?).

Dongqin Bi

Certified efficiency at Newport, 21.0%, Dec. 2015 (hysteresis-free)

Voc = 1.13 VJsc = 23.8 mA/cm2FF = 0.78PEC = 21.0 %

Our Certified Champion Cell

Certified world record is 22.1% (March 2016) by Seok et al.

Dr. Xiong Li

2016

Vacuum flash treatment produces smooth and shiny perovskite films of high quality

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)

Cs additive

Michael Saliba

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

2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted) 32

What happens if caesium (Cs) is added? (Triple cation mixtures)

Disappearance of the yellow phase and PbI2 excess

10 20 30 40 50

x = 15%

x = 10%

x = 5%Inte

nsity

(a.u

.)

2 (°)

x = 0%δPbI2

10 20 30 40 50

x = 15%

x = 10%

x = 5%Inte

nsity

(a.u

.)

2 (°)

x = 0%

Csx(MA0.17FA0.83)(1-x)Pb(I0.83Br0.17)3 (nominal precursor composition)written as CsxM

2016-03-01 Michael Saliba, Triple Cations for Stability, Reproducibility and High Efficiency (submitted) 33

Devices cross sectional SEM

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

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?

Planar PSC Structures Using ALD SnO2

Dr. LudmillaSteier

Dr. Juan-PabloCorrea-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)

36

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

70 180

Chemical Bath Deposition

Perovskite: Triple cation protocol

38

Yields High Efficiencies

PCEs = 20.8%

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!

2016-09-13, Michael Saliba, Multication perovskites

Device results – New systemM. 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. GrätzelScience I, online, Thursday Sept. 29

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

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 1000hProblem:• 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

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%

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. 29Federico Bella*, Gianmarco Griffini, Juan-Pablo Correa-Baena*, Guido Saracco, Michael Grätzel,

Anders Hagfeldt, Stefano Turri, Claudio Gerbaldi

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?

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

….