15e Congrès photovoltaïque national, Lausanne, March 23, 2017

Latest achievements in the field of dye sensitized andperovskite solar cells

Anders HagfeldtLaboratory of Photomolecular Sciences (LSPM)

Welcome to Lausanne!

• Brief update on Dye-sensitized solar cells

• Minimizing internal potential losses

• Cu-complex redox species

• Perovskite solar cells

• Mixed compositions

• Stable perovskite solar cells

DSC niche applications

Vertical –Facades

North-West Orientation

Intermittent and Diffuse Light

Design –Appearance

Indoor

HighVoltage

Photovoltaic hedge as power source for electric car charging station

5

Industrialization of DSSC - status

Consumer Electronics - YES

Large-scale electricity production – Breakthroughs needed!

Requires < 0.5$/Wpeak

DSC in buildings – ?

Logitech

G2E, Switzerland. World Expo Milan, 2015

TiO2

Light

e-e-

E

I- /

I3-

e-

DyeTCO

Electrolyte

e-

hn

e-

e-

Dye-sensitized

Solar Cells

DSSC Operational Principles

How to improve? Need to change the electrolyte system.

Efficiencies > 10% for all 3 complexesBest efficiencies:10.5% at 1 sun11.7% at 0.5 sun

Dye: Dyenamo LEG4

Recent results of ”Zombie – cells ” and indoor performance

For IoT: 200 Lux (IKEA Bulb): DSSC better than GaAs

DSSC ideally suited for indoor light, accepted by Nature Photonics

Dried outCu-complexlayer

Perovskite Solar CellsSeveral Device Structures and Applications

Planar

Mesoscopic

Inverted

• Lasing• Light emitting devices• Tandem solar cells

• Photodetectors• XRD-detection• …...

CH3NH3PbI3: Ambipolar semiconductor band gap 1.55 eVBohr 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 heterojunctionsolar cells

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-performancesolar cells. Nat. 517, 476-480 (2015).

Certified efficiency at Newport, 21.0%, Dec. 2015 (hysteresis-free)Nature Energy DOI: 10.1038/NENERGY.2016.142

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

Our Certified Champion Cell

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

Cs additive

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)

Devices cross sectional SEM

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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

2016-09-13, Michael Saliba, Multication perovskites

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Device results

• Highest PCE: 21.6% stabilized

• Highest 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!

• 4% External Radiative Efficiency (ERE, Electroluminescence)

Stability tests

Stability: 95% is retained after 500h of continous operation (MPP) at 85 oC and full illumination

• Gold/spiro is not a stable contact at high temperaturesACS Nano DOI: 10.1021/acs.nano.6b02613

• PTAA Polymer as HTM

Stress test: 85 oC, full illumination, MPP for 500h (in N2 atmosphere)

Summary

• Dye-sensitized solar cellsDesign, building integration, minimize electron transfer driving force

• Dye-sensitized solar fuelBuild on materials, devices,and characteriation techniques from DSSC

• Perovskite solar cellsCompete and join silicon cells (tandem devices)

Integrated photoelectrochemical-photovoltaic devices

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