organic photovoltaic: challenges and opportunities dr. kallol mohanta psg institute of advanced...

Organic Photovoltaic: Challenges and Opportunities

Dr. Kallol MohantaPSG Institute of Advanced Studies

Coimbatore, Tamilnadu.

Seminar on Solar Installations, Economics, Business opportunities and New Trends in Solar Energy Systems

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Scope of discussion

• Categorization of photovoltaic technologies• What is Organic Photovoltaic (OPV)?• Brief timeline• Present situation• Challenges • Opportunities

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Categorization of photovoltaic technologies

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• 1st generation• 2nd generation• 3rd generation• 4th generation

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Conventional inorganic p/n junction solar cell

Solar Cell

Silicon

Compound Other

Cry

sta

lline

Am

orp

ho

us

Poly

cry

sta

lline

II•VI CdS CdTe …

III•V GaAs InP …

I•III•VICuInSe..

Org

an

ic DSS

C

Sin

gle

Cry

sta

l

Pero

vskite

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What is Organic Photovoltaic (OPV)?An organic solar cell or plastic solar cell is a type of polymer solar cell that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect.

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Organic Semiconductor Inorganic Semiconductor

Comprise of main “C”, “H” and “O”, also usually involves “N”, “S”, “P” …

All elements

Tailored properties Depend on the material

Weak interaction Strong interaction

HOMO, LUMO Valence Band, Conduction Band

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What is Organic Photovoltaic (OPV)?

perylene

pentacene

polythiophene

ppvpedot

pthalocyanine

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LUMO

HOMO

n- type p- typeAmbipolar

e- e-

h+ h+

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These cells are made by sandwiching a layer of organic electronic materials between two metallic conductors. The potential created by the different work functions helps to split the electron-hole pairs.

Bilayer cells contain two layers in between the conductive electrodes. The two layers have different electron affinity and ionization energies, therefore electrostatic forces are generated at the interface between the two layers.

A three-layer (two acceptor and one donor) stack. The implementation produced high open-circuit voltages and absorption in the visible spectra and high short-circuit currents.

Bulk heterojunctions have an absorption layer consisting of a nanoscale blend of donor and acceptor materials. The large donor-acceptor interfacial area results in a higher likelihood for the short-lived excitons to reach an interface and dissociate.

The electron donor and acceptor are mixed in such a way that the gradient is gradual. This architecture combines the short electron travel distance in the dispersed heterojunction with the advantage of the charge gradient of the bilayer technology.

Similar to the graded heterojunction, however, the acceptor material is prepared directly from the donor polymer in a post-polymerization modification step.

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Junction types: 1. Single layer Junction types: 1. Single layer 2. Bilayer

Junction types: 1. Single layer 2. Bilayer3. Discrete heterojunction

Junction types: 1. Single layer 2. Bilayer3. Discrete heterojunction4. Bulk heterojunction

Junction types: 1. Single layer 2. Bilayer3. Discrete heterojunction4. Bulk heterojunction 5. Graded heterojunction

Junction types: 1. Single layer 2. Bilayer3. Discrete heterojunction4. Bulk heterojunction 5. Graded heterojunction6. Continuous heterojunction

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Identified specific USPs (or combinations) for OPV:• Harvesting Factor: The unique behavior of OPV at high temperature (in the sun)

and at low light, allows for better energy harvesting than its efficiency at STC would indicate.

• Good form-factor: Devices can be designed into many forms on light weight and flexible substrates and supports

• Transparency: OPV offers truly transparent product, in which the transparency can be tuned to meet the applications

• Aesthetics: The appearance of OPV modules can be designed by tuning the color, the shape and the thickness

• Scalability: OPV has the perspective of a highly automated, low energy consuming and low-cost production through fast printing and (vacuum) coating techniques.

• Environmental profile: It is expected that OPV will have an excellent sustainability profile in terms of energy pay-back time and carbon footprint. No heavy metals are used, in contrast to CdTe (cadmium) or perovskite PV (lead).

These (combined) USPs can lead to all kind of new

applications in different market segments, where the

OPV functionality can be integrated in a wide variety

of structures and objects not covered by the technologies

present today.

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Brief timeline

1950

BELL DEVELOPS SOLAR CELLBell Laboratories develops the first inorganic solar cell based on silicon. Three years later, US Patent Office issues a patent to Bell Labs for 'Solar Energy Converting Apparatus'

1958

KEARNS/CALVIN CREATED BILAYERED DEVICEDavid Kearns and Melvin Calvin create a 'bilayered device' using magnesium phthalocyanine and oxidized tetramethyl p-phenylenediamine.

1962

SHOCKLEY-QUEISSIER LIMITThe "detailed balance limit of efficiency," also known as the Shockley-Queissier limit, is established, giving bounds to the achievable efficiencies of photovoltaics.

1974

USE OF OHMIC CONTACTS IN OPV DEVICE ARCHITECTUREP.H.Fang devises equation to convert between apparent efficiency and real efficiency, leading to the idea of improvement of efficiency by Ohmic contact with organic materials.

1978

OPV BREAKS THE 1% BARRIERResearchers from Exxon Mobil report an OPV device with 1% efficiency (corrected) using semi-transparent aluminum electrodes.

1986

BILAYER ORGANIC PHOTOVOLTAIC CELLTang from Eastman Kodak creates the first two-layer organic thin film, in which a single layer of organic material is sandwiched between two dissimilar electrodes. This first two-layer cell had a .95% power conversion efficiency, which, at that time, was one of the highest reported efficiencies.

1991

FIRST BULK HETEROJUNCTION PV IS MADEScientists from Osaka University make the first dye/dye bulk heterojunction PV by co-sublimation. The cell had an efficiency of 0.7%

19931994

20012002

2005 20092011

20122013

FULLERENE USED AS ELECTRON ACCEPTORScientists from UC Santa Barbara report photoinduced electron transfer from MEH-PPV to C60.

POLYMER PHOTOVOLTAIC CELLS ARE HEREScientists from UC Santa Barabara report solar cells based on MEH-PPV and C60.

PLASTIC SOLAR CELLSC.J. Brabec et al. use plastics and increase the power conversion efficiency to 3%. Buckminsterfullerene is also used for ultrafast electron transfer. The recent improvements in efficiency enhanced emphasis in the field from multiple groups worldwide.

HYBRID NANOROD-POLYMER SOLAR CELLSPaul Alivisatos and co-workers report P3HT-CdSe Nanoparticle device with PCE of 1.7%.

STABLE ALL NANOCRYSTAL CELLSI. Gur et al. synthesize ambient-environment-stable, ultrathin all inorganic nanocrystal solar cells.

ALL-POLYMER SOLAR CELLHolcombe et al. of U.C. Berkeley synthesize an all-polymer solar cell form Grignard Metathesis polymerization

9.2% EFFICIENCY OPVMitsubishi Chemical announces the production of 9.2% PCE OPV.

USE OF ORGANOMETAL HALIDE PEROVSKITESThe use of organometal halide pervoskites as light absorbers results in 10.9% efficency by Snaith and co-workers

HELIATEK ANNOUNCES 12% EFFICIENCYHeliatek announced that they are able to make an organic solar cells (with small molecules) with 12% efficiency.

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http://www.tiki-toki.com/


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Present situation

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Ene. Env. Sci., 2013, DOI: 10.1039/C4EE00260A


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Present situation

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ACS Nano, 2012, DOI: 10.1021/nn304410w


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Present situation

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Nat. Phot., 2013, DOI: 10.1038/nphoton.2013.207


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Present situation

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www.heliatek.com/


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Challenges4 ‘M’ factors

• Materials

• Morphology

• Mechanism

• Manufacturing

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ChallengesMaterials

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Nat. Phot., 2012, 6, 180

J. Am. Chem. Soc., 2011, 133, 3284

Acc. Chem. Res., 2010, 43, 1227


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ChallengesMaterials

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Surf. Interf. Sci., 2010, 42, 1010J. Phys. Chem., 2010, 114, 5344


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ChallengesMorphology

In pristine form / solution

During deposition

During annealing / post-deposition treatment

Introduced by varying concentrations or changing solvent

Different deposition methods or varying deposition parameters

Tuning annealing temp. and time and other factors

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ChallengesMorphology

Morphology Vs charge extraction

Morphology Vs charge transport

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Sci Rep., 2015, DOI: 10.1038/srep08286Sci. Rep., 2013, DOI: 10.1038/srep03425

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Challenges

PV technology Efficiency (lab) Efficiency (commercial) % decrease

c-Si 25 20.1 (SunPower) 19.6

p-Si 20.4 14.6 (Schott) 28.4

a-Si 10.1 5.1 (UniSolar) 49.5

CIGS 19.6 12.5 (Qcells) 36.2

CdTe 16.7 12.5 (First Solar) 25.1

DSSC 11.0 1.74 (G24 Innovations) 84.2

OPV 10.0 1.65 (Konarka) 83.5

Performance gaps for different PV technologiesManufacturing

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Prog. Photovolt.: Res. Appl., 2011, 20, 12

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ChallengesManufacturing

Morphology depends on manufacturing process - drying techniques - role of different additives for viscosity - maintaining purity of material at interfaces

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Mater. Today, 2012, 15, 36

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Challenges

Materials

MechanismMorphology

Manufacturing

Green, cheap, defectless, ordered materials synthesis Charge separation process & role of interfaces Morphology formation & its effect on functionalization Simplification and precision of critical manufacturing processes

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Opportunities

New PV applications are emerging• Cars, trains, weak roofs, not ideal orientations, facades, portable applications,

see-through, ...

PV market keeps on growing and demand keeps on increasing

Not ‘one-technology’ will suit all PV applications• High efficiency Si solar cells for PV power plants, regular rooftop

systems, and specific applications• Other technologies for integrated solutions

Other parameters start to play• Flexibility in patterns and shapes, aesthetics• Good response to indirect light• Cost/m2rather than cost/Wp

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Opportunities

c-Si p-Si a-Si CdTe OPV0.0

0.5

1.0

1.5

2.0

2.5

EP

BT

(yr)

A

Energy Pay-Back Time

c-Si p-Si a-Si CdTe OPV0

5

10

15

20

25

30

35

CO

2 em

issi

on (

g eq

./kW

h)

A

Carbon emission

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PV TMS Workshop, ANL, Argonne, 2013

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OpportunitiesTaking the USPs of OPV, specific market segments have been identified:• Transportation segment:

-Integration of OPV in mobile applications via vehicles like cars, freight trucks and trains for climate control in the vehicle and prevention of discharging of batteries

• BIPV segment:-Windows in office buildings, both new construction and retrofit, façade elements between glass or on metal, aluminum or concrete

• Off grid remote sector:-Flexible, light-weight, fast-deployable structures to be applied in shelter, sun shades, greenhouses

• Small Autonomous Network Device (SAND):-Charging function for (indoor) sensors, electronic devices, …Important for market intro, but limited large-scale production

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INDUSTRIAL TECHNOLOGIES, IMEC Athens 2014

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Opportunities

Transport: Automotive BIPV: Glass, Metal, Facades, ….

Fast Deployable Structures: Shelters, Sunshades, ….

Thin and lightweight Thin and lightweight Lightweight

Color tunable Color tunable Bendable

Transparent and conformable

Semi-transparent and conformable

Semi-transparent, conformable and custom shaped

Printed OPV Integrable to different building material

Off-grid charging in remote places

Power output efficiency and low energy pay back time

Efficiency and heat management

High power output

Green technology Green technology Green technology

Assessment of market applications

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Opportunities

Transport: Automotive BIPV: Glass, Metal, Facades, ….

Fast Deployable Structures: Shelters, Sunshades, ….

Efficiency: Solar is not main power source, only back-up

Efficiency: 6-8% is considered good starting point, especially when translucent

Efficiency: large available area compensates for power requirements

Lifetime: 3-5 years acceptable

Lifetime: strongly determined by ROI-timeInfluenced by incentives, directives

Lifetime: mostly temporary constructions (/seasonal)

Cost: not determined by real PV cost, but by added value

Cost: not determined by PV cost

Cost: has to be balanced with potential gain

OPV has reached a level of standard metrics that allows to go for the next step OPV can penetrate above markets even with current metrics

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Summery

• OPV is a 3rd generation solar technology.• Currently highest 12% efficiency of OPV recorded at

laboratory environment.• Technical issues like materials, morphology, mechanism

and manufacturing have to be resolved or improved.• Marketing assessment shows that different

technologies should collaborate to meet the demands of new photovoltaic applications.

• With the present development in this field certain applications can be addressed.

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Thank you

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organic photovoltaic: challenges and opportunities dr. kallol mohanta psg institute of advanced...

Documents

organic photovoltaic

organic solar cell

organic electronics

single layer junction

photovoltaic effect

bilayer junction types

absorption layer

conductive organic polymers