Thin-Film Photovoltaics R&D: Innovation, Opportunities_Ennaoui

Thin-Film Photovoltaics R&D: Innovation, Opportunities

Ahmed Ennaoui Helmholtz-Zentrum Berlin für Materialien und Energie

[email protected]

IRESEN ´s Event for the launch of calls for proposals 2013 Casablanca, January 30th, 2013

This material is intended for use in lectures, presentations and as handouts to students, it can be provided in Powerpoint format to allow

customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage.

Flexible PV OPV Nanoparticles

Tandem Solar cell Silicon Solar cell

http://www.iresen.org/index.php

Thin Film Solar Cell

DSSC

Advanced Thin-Film Devices

Novel Materials and Device Concepts

Advanced Analytics and Modelling

Solar Fuels

• Chalcopyrite-Type Semiconductors

• Silicon Photovoltaics

• Directed toward long-term goal of

producing cost-effective and more

efficient devices

• Advanced interface analysis

• Charge carrier dynamics

• Microstructure an defect analysis

• Device and material characterisation

• Development cost-effective PV

hybrid systems directly convert

sunlight into stored chemical

energy producing hydrogen via

water splitting

Solar Energy Division in Helmholtz-Zentrum Berlin für Materialien und Energie

Kompetenzzentrum Dünnschicht- und

Nanotechnologie für Photovoltaik Berlin

Thin-film module production.

R&D education and training

R&D of industrial processes

R&D of promising high-risk concepts

Up-scaling of successful R&D of HZB

International Summer University on Energy

4 Research Topics

Thin-Film Photovoltaics: Innovation and Opportunities

Third Generation: Molecular devices:

Dye sensitised DSSC

Organics OPV

Quantum structured solar cells

Innovation

Thinner

Efficient

Faster Second Generation

Cu-chlacopyrite compounds (CIGSSe)

Emerging structure compounds (CZTSSe)

Cadmium telluride (CdTe)

Amorphous and µ-crystalline silicon

Scarcity of materials

Monolithic integration

Lower production costs

Large area deposition

Energy pay back time

Implementation in building

Highlight

Introduction: VLSI Technology vs. Solar Cell and Moore´s law

The first practical photovoltaic cell was invented

at Bell Laboratories in 1954 (few %)

1941, first silicon solar cell was reported

(US Patent 240252, filed 27 March 1941)

http://www.intel.com/technology/silicon/mooreslaw/

Solar Cells: Efficient, Thinner , Cheaper, Faster

Pentium 4 has around 55 million components per chip (2003)

Number of transistors doubles every two years

Computer: Faster, cheaper, storing more data

Quelle: G. Willeke, ISE

First transistor

http://www.intel.com/technology/silicon/mooreslaw/

Introduction: PV Module production cost evolution

CdTe

Record Cell EFFiciency (%)

17.3

Record Module EFFiciency (%)

15.5

Aver. Module EFFiciency (%)

12.5

Prod. Capacity 2011 (MWp/yr)

2200


2700

CIGSS

Minimodule

Cell (0.5cm2)

17.8

19.7%

Record Module 14.5

Aver Module 12.6


500


1000

Crystalline -Si PV prices dropped by over 40% EFFICIENCY ≈15 % 0.8 - 0.6 €/W

CdTe (First Solar) / EFFICIENCY ≈12.2 % 0.67 €/W

CIGSS Solar Frontier EFFICIENCY ≈ 12.6% 0.55 - 0.42 €/W

a-Si:H/mcSi / (Oerlikon,ThinFab140) / EFFICIENCY 2012 ≈ 10.8% (154 W) 0.35 $/W

New Record (January 2013)

Quelle: Alberto Mittiga/ENEA / and H.W. Schock Annu. Rev. Mater. Res. 2011. 41:297–321

Introduction: Storage: High capacity, Higher Operating voltage, and Long Cycle

Quelle

http://www.treehugger.com/files/2008/02/lithium-ion_battery_factory.php

LITHIUM BATTERIES:

• high energy density (3 times lead-acid).

• Application spans beyond the electronics market

• Li-ion nanophosphate is inherently safer.

• Safe non-flammable electrolytes.

Structurally stable compounds, such as: LiFePO4

High capacity, Higher Operating voltage, and Long Cycle

Ahmed Ennaoui / Helmholtz-Zentrum Berlin für Materialien und Energie

Introduction: Key Task of Photovoltaic

Power [Watt/cm2] = Voltage [Volt ] x Current density [A/cm2]

PV products can be optimized for

location, with lower associated financial

risk based on predictable performance

Key aim is to generate electricity from solar spectrum

EFFECIENCY INCREASING

LESS AREA

LESS MATERIAL

COST FOR PV REDUCED

LOW €/Wp

Materials with small Band gap

But low voltage

Excess energy lost to heat

Generating a large current (JSC)

Materials with large band gap

But low current

Sub-band gap light is lost

Generating a large voltage (VOC)

Two challenges

Solar cell design

versus

solar spectrum

Voltage [Volt ]

J SC [

A/c

m2 ]

Po

wer

[W

att/

cm2 ]

VOC 0

JSC maximum

power

point

Jm

Vm

Vm x Jm

AM1,5

Efficiencies beyond the Shockley-Queisser limit

500 1000 1500 2000 25000

200

400

600

800

1000

1200

1400

1600

Le

istu

ng

sd

ich

te [

W/m

2µ

m]

AM15

GaInP

GaInAs

Ge

Wellenlänge [nm]

(1) Lattice thermalization loss (> 50%)

(2) Transparency to h < Band gap

(3) Recombination Loss

(4) Current flow

(5) Contact voltage loss

Not all the energy of absorbed photon

can be captured for productive use.

(Th. Maxi efficiency ~32% ).

source

1.7 eV

1.1 eV

0.7 eV

R.R. King; Spectrolab Inc., AVS 54th International Symposium, Seattle 2007

Optimistic calculation Best commercially available cells 37% efficient at 25°C.

75% efficient 0.30 × 0.75 × 850 ≈ 200 W/m2 of electrical power.

At $200/m2 the capital cost would be $1.50/W.

Si 14

Si

Ge

32

Ga

31

As

33

Cd

48

Te

52

P

15

In

49

Al

13

Sb

51

Cu

29

Se

34

In

49

31

IIB IIIB IVB VB VIB IB

C

6

B

5

Zn

30

Sn

50

S

16

O

8

N

7

Periodic Table

ZnS

Ge

GaAs

CdTe

InP

AlSb

CdS

Scientific Background

Silicon

IV

Tetrahedrally coordinated

4...

mn

mqnq MN

n,m atoms/unit cell

Grimm-Sommerfeld rule

Source: Ennaoui Osaka seminar

CuInxGa1-xSe2

Cu2SnZnSe4

Diamond Structure

I-III-VI2 II-IV-V2

AlxGa1-xSe2 Cu(In,Ga)Se2

Cu2(ZnSn)Se4

Zincblende

Structure II-VI III-V

Common Symbol + -

Si 14

Ge

32

Ga

31

As

33

Cd

48

Te

52

P

15

In

49

Al

13

Sb

51

Cu

29

Se

34

In

49

31

IIB IIIB IVB VB VIB IB

C

6

B

5

Zn

30

Sn

50

S

16

O

8

N

7

Periodic Table

Silicon (IV): Diamond Structure

Doping Technology of Silicon: pn junction of Silicon

PERL: passivated emitter and rear cell ( 25%) Martin Green, UNSW’s cell concepts PIP 2009; 17:183–189 / http://www.unsw.edu.au/

Device fabrication 1. Surface etch, Texturing

2. Doping: p-n junction formation

3. Edge etch: removes the junction at the edge

4. Oxide Etch: removes oxides formed during diffusion

5. Antireflection coating: Silicon nitride layer reduces reflection

Cells

Purifying the silicon:

STEP 1: Metallurgical Grade Silicon (MG-Silicon is produced from SiO2 melted

and taken through a complex series of reactions in a furnace at T = 1500 to

2000°C.

STEP 2: Trichlorosilane (TCS) is created by heating powdered MG-Si at around

300°C in the reactor, Impurities such as Fe, Al and B are removed.

Si + 3HCl SiHCl3 + H2

STEP 3: TCS is distilled to obtain hyper-pure TCS (<1ppba) and then vaporized,

diluted with high-purity hydrogen, and introduced into a deposition reactor to form

polysilicon: SiHCl3 + H2→Si + 3HCl Electronic grade (EG-Si), 1 ppb Impurities

STEP 1

STEPE 2 and 3

Electronic

Grade Chunks

Source: Wacker Chemie AG, Energieverbrauch: etwa 250kWh/kg im TCS-Process, Herstellungspreis von etwa 40-60 €/kg Reinstsilizium

Ingot sliced

to create wafers

Making single

crystal silicon

Czochralski (CZ) process

crucible

Seed crystal slowly grows

Microelectronic

1G: Crystalline Si PV technology

Nanotechnology in Roman Times: The Lycurgus Cup

Plasmons of gold nanoparticles in glass reflect green, transmit red Because of plasmonic excitation of electrons in the metallic particles suspended within

the glass matrix, the cup absorbs and scatters blue and green light – the relatively short

wavelengths of the visible spectrum. When viewed in reflected light, the plasmonic

scattering gives the cup a greenish hue, but if a white light source is placed within the

goblet, the glass appears red because it transmits only the longer wavelengths and

absorbs the shorter ones.”

Nanosacle: 1m/1000 000 000 Photonic and Plasmonics

Quelle: http://daedalus.caltech.edu/research/plasmonics.php and US Department of Energy

Mesoscale structure • Defects and interfaces are functional at the mesoscale.

• Control of light is critical for next generation high performance solar cells.

Photonic (A) SEM image of a nanodot focusing array

(B) SP intensity showing subwavelength focusing

Ekmel Ozbay Sciences 311 (2006) pp. 189-193

1µ

Catalytic reactive surface

Nanotechnology: Photonic/Plasmonic/Solar cell

Nanosynthesis Modeling and Simulation Characterization

Plasmonic

Glass, Metal Foil, Plastics

CdTe based device

Quelle: Noufi, NREL, Colorado, USA,

Substrate configuration *CIGS based device

CdTe and CIGS Thin Film Solar cells (2nd. Generation)

Superstrate configuration

Common features

p-type materials due to intrinsic defects and fast diffusing impurities (Cl in CdTe and Na in CIGS).

Heterojunction made using an high band gap buffer layer CdS (2.42 eV), ZnS (3.6 eV)

Efficiency for Polycrystalline Thin-Film Solar cells larger than their single crystal counterpart.

Excellent outdoor stability (with good lamination) and radiation hardness

Tolerance to wide range of molecularity Cu/(In+Ga)

Yields device efficiency of 17% to 20%

Equilibrium vapor pressure of Cd and Te much

higher than that of CdTe

The pure phases tend to evaporate

R&D Directions

In situ optical processing

Optimal range for efficient thin film solar cells: 22-24 at % of Cu

a-phase highly narrowed at room temperature

Possible at growth T from RT to 550°C

b-phase (CuIn3Se5) defect phase defect pairs (VCu, InCu)

d-phase (high-temperature) Cu & In sub-lattice

Cu2Se • built from chalcopyrite structure by • Cu interstitials Cu-In anti sites • Melting point at ca. 530°C surfactant for recristallization (large grains)

Reduce the manufacturing cost.

Through efficiency improvements.

Reduce the thickness of CIGS.

(0.7 µm thickness and 17% efficiency)

Interface engineering.

Band gap adjustment: 1.03eV-1.7 eV.

Cadmium free buffer layer R&D.

Low cost processing.

1. Glass

2. Mo

CIGS

Buffer

ZnO

Technology: Monolithically Integrated PV

P1

Step 1: Deposition of Cu, In,Ga (Se)

(sputtering, codeposition, Electrodeposition)

Step 2: Rapid Thermal Processing (RTP)

Pulsed

Laser

Front ZnO of 1 cell is connected to the back Mo contatc of the next cell

Se Cu

Ga In

Cu(In,Ga)Se2

Monolithic integration for series connection of individual cells

P3 P2 P1

- P1: Series of periodic scribes to defines the width of the cells

- P2: Mechanical scribes after the absorber and buffer layer

- P3: Mechnical scribes after the window deposition

Si

Module

Vmodule= Vcell x Ncell

24 V for battery charging

CIGS manufactured on low cost glass substrates.

CIGS manufactured on flexible substrates.

Enables access to the largest PV markets.

Short energy pay back time and less energy consuming process.

Compatible with existing photovoltaic system infrastructure.

Easy to integrate into Building (BIPV) market.

Strong point of CIGS

PowerFLEX™ Modules

http://www.globalsolar.com

BIPV thin-film CIGS façade

Honda building in Japan

Light weight

3.5 kg/m2

EFFICIENCY

10.5% to 12.6%

50% more efficient than flexible a-Si

Evolution and Record efficiency

20.4%

~11.1%

~12%

19.7% Cadmium free

CIGSS Jan. 2013

Flexible substrate

CIGSe Jan. 2013

CZTSSe

IBM New York 2013

OPV

2013

EFFICIENCY 20.4% for Cu(In,Ga)Se2 or (CIGS) on polymer foils

(Swiss Federal Laboratories EMPA achieved January 2013)

EFFICIENCY 12% for PV (OPV)

(Heliatek: German organic January 2013 )

EFFICIENCY 11.1% for ink-based Cu2ZnSn(S,Se)4 (CZTS)

(IBM’s Materials Science team + Solar Frontier, Tokyo + DelSolar )

Big issue: CIGS and CZTS

on flexible substrate

Problem: Materials availability

Modules

(EFF ≈11%)

Metal

Required

(Tonn/m2)

Reserves

1998

Tonn

Productio

n

1997

Tonn/yr

CdTe

(3 µm) Te

180 t/GWp

20000 290

CIGS

(2 µm) In 98 t/GWp 2600 290

2011 Total PV Annual production≈37 GWp/yr (2 GWp/yr due to CdTe and 1GWp/yr due to CIGS)

Worldwide continuous electricity consumption : 15 Terawatts

Fthenakis, Renewable and Sust. Energy Rev., 13, 2746-2750, 2009 / http://www.compoundsemiconductor.net/csc/news-details.php?id=19735415

CZTS Thickness 1 μm and an efficiency of 10% needs 10 g/m2 of material

CZTS PV cells could potentially yield up to 500 GW/year.

CIGS and CdTe contain rare elements that limit their manufacturing < 100 GW /year.

Recycling issue for In and Te

B. A. Andersson Prog. Photovolt. Res. Appl. 8, 61 (2000) / Wadia et al. Environmental Science and Technology 2009, 43, 2072

U.S. Geological Survey Fact Sheet 087-02

Design to high efficiency solar cells

Light trapping

Reflection Loss: ARC

Material

Parameter

absorption Important cost factor

thikness

€

αW

p

eαL1

11 R)(1 η

λ

hc

e

)J(

Φ(λ)

1

N

Nη

photons

in

electron

out

Decisive Material

Parameter

The band gap

0.3 0.5 0.7 0.9 1.1

20

0

40

60

80

100

0

1

2

3

4

5

Nu

mb

er o

f S

un

ligh

t P

ho

ton

s (m

-2s-1

mic

ron

-1) E

+19

R E

xter

nal

Qu

antu

m E

ffic

ien

cy, %

c-Si:H junction a-Si:H junction

AM 1.5 global spectrum

Wavelength, microns

a-Si:H/c-Si:H Cell Spectral Response

Textured TCO

a-Si

Top cell

Back

Reflector

Glass

substrate

Thin film mc-

Si

Bottom cell

GE

λ0λsc dλ .dα-exp . )().ΦR(1 . η(λ). qJ

Light from the sun

C10x 1.6e

][A.mCurrent N

19

-2electron

out

energy[J] photon

][J.m EnergyInput N

-2Photon

in

a-Si/μc-Si Tandems: Tandem Cell Design

Source PVComB/Rutger Schlatmann

a-Si/μc-Si Tandems: Lab Record Cells (1 cm², stable)


Triple Cell Optimization


Triple Cell: Improvements of optical and electrical properties

Interfaces, Zeman& Krc, J.Mater. Res. Vol23(4) 889-898 (2008)


Basic research

Optical + Electrical

• 3th. Generation: OPV solar cells Provide Earth abundant and low-energy-production PV solution.

Organic semiconductors: Abundant: ~100,000 tons/year

• Key component The electron acceptor

Light harvesting material (conjugated polymer)

Organic Photovoltaics (OPV): Molecular Perspective

Aluminum

Absorber Polymer Anode

ITO Substrate

Donor polymer (i.e. P3HT)

absorbs light generating an exciton

Exciton must diffuse to the

Donor/Acceptor interface

Status (Dresden/Germany, 16. Januar 2013 / http://www.heliatek.com/)

New word record 12% efficiency by Heliatek GmbH

Polymer-Fullerene Heterojunction Cells

Electrons travel to the back

electrode and Holes travel to the

front electrode

~2

00

nm

th

ick

OPV: R&D

Large Scale Printing Konarka

Important issue:

optimizing the band gap and LUMO-LUMO offset

Donor acceptor concept

Quantum size effect

To to varie the band gap

HOMO-LOMO

Quantum Size effect

Nanosynthesis

R. D. Schaller, V. I. Klimov, Physical Review Letters, 2004, Vol. 92.

Excellent review on Concept of Inorganic solid-state nanostructured solar cells

T. Dittrich, A. Belaidi, A. Ennaoui Extremely Thin Absorber (ETA)

Solar Energy Materials and Solar Cells, Volume 95, Issue 6, June 2011, Pages 1527-1536

ZnO

nanorodes

Nanocrystalline based Solar cells

Electron holes photogenerated

Immediately injected in mesoporous TiO2 (or ZnO NRs)

Photosynthesis

CO2

Sugar

H2O

O2

OPV: Research direction

glass or plastic

transparent conductor

organic-inorganic

metal

Organic multijunction architecture ((Including Encapsulation and reduce cell degradation)

NC Nanoparticles

Nanosynthesis,

Nanotechnology

Organic / Polymer

Chemistry Coating

Technoques

Contact

materials

Contact

materials

Glass

Ag

ZnO-NRs

ZnPc:C60 C60

MoO3

ZnO-NR / C60 / ZnPc:C60 / MoO3 / Ag

200 nm

First solar cells with ZnO-NRs and small molecules / Eff. 2.8%

HZB-Patent WO 2008 / 104173 (Rusu et al.)

H2O→2H2+O2 ∆V=1.23V, ∆G=238kJ/mol

R&D: Hydrogen Fuel

Source: Mildred Dresselhaus, Massachusetts Institute of Technology

D

D D D D D

Heterogenous process

Homogenous process

Thin Film Material Research Band gap must be at least 1.8-2.0 eV

To absorb most sunlight spectrum

Compatible with Redox potentials

Fast charge transfer

Stable in aqueous solution

Nanoparticle catalysts

Nanoparticle: Surface-to-volume ratio

Nathan Lewis, Caltech

(1) Two spatially separated electrodes

coated with catalysts placed in

water.

(2) Cathode produced hydrogen,

and anode produces oxygen

D

D D

D

D

R&D: Fuel Cells

O2- and H+ combine Energy is given off in electron form and gives off power to run an engine

The “waste

products” are

water and heat

Catalyst = Pt Very

expensive

Minimize the Pt quantity

Improve the active layer structure

Propose new materials

Fuel Cell uses a constant flow of

H2 to produce energy.

Reaction takes place between

H2 and O2 electrical energy.

Platinum for a reaction that ionizes the gas

O2 is ionized to O2-

H2 is ionized to 2H+ 2H+ + O2- = H2O

The most common fuel cell uses • Proton Exchange Membrane, or PEM

• Need of alternative catalyst (Platin is expensive)

http://www.ballard.com/

Advantages Zero emission

No dependence on foreign oil

Ability to harvest solar and renewable energy

Not many moving part in a car

Hydrogen weighs less than gasoline :

car would not need as much energy to move

R&D Fuel Cells: Platinum plate is very expensive. Batteries: Lithium batteries: high energy density (3 times lead-acid). Safety issue: Instead of oxygen releasing (LiCoO2) Structurally stable alternative compounds, e.g. LiFePO4 Chemistry and anode/cathode design Li-ion nanophosphate

Storage (Fuel Cell, Batteries)

Final Remarks

others

0.3 GW

CIS

0.9 GW

CdTe

2.05 GW

Amorphous/microcrystalline silicon

1.26 GW

Monocrystalline silicon

11.5 GW

Multicrystalline silicon

21.2 GW

2011 Total Production : 37 GW Quelle: http://www.photon-international.com

Weak point of c-Si:

•Indirect bandgap 1 eV

•Low light absorption

•Huge loss

•Production Cost

Strong point of c-Si:

• High module efficiency: up to 20%

• High stability and reliability

• Mature and “modular” technology

Thin Film Solar PV

Inexpensive ways to produce energy, (few cts/kWh)

Thinner, Efficient, Faster, Cheap

Large area deposition

Energy pay back time

Implementation in building

Scarcity of materials

Monolithic integration

Lower production costs

Cu(In,Ga)(SSe)2 20.4% flexible ; 19,7% Cd free

Cu2ZnSn(S,Se)4 Printing technology?

OPV new record 12% Printing technology?

DSSC (11%) Reliability/Degradation, solid electrolyte

Quantum devices (long term Research topic)

15 %

0.8 - 0.6 €/W

12.6%, 0.8 - 0.6 €/W

12.2 % , 0.67 €/W

10.8% (154 W) 0.35 $/W

IRESEN Event for the launch of calls for proposals 2013 Casablanca, January. 30th, 2013

This material is intended for use in lectures, presentations and as handouts to students, it can be provided in Powerpoint format to allow

customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage.

Flexible PV OPV DSSC Nanoparticles

Thin Film Solar Cell Tandem Solar cell Silicon Solar cell

http://www.iresen.org/index.php

Vielen Dank für Ihre Aufmerksamkeit Thank you for your attention شكرا لكم على اهتمامكم

Morocco is going to translate from being a net importer of energy and a country facing

water shortage issues, into a producer of clean renewable energy and water in the region.

ينبغي على المغرب أن يترجم من كونه مستوردا للطاقة وبلد يواجه قضايا نقص المياه

والمياه في المنطقة إلى منتج للطاقة المتجددة النظيفة

Big Challenge التحدي الكبير

Thin-Film Photovoltaics R&D: Innovation, Opportunities_Ennaoui

Technology

Transcript of Thin-Film Photovoltaics R&D: Innovation, Opportunities_Ennaoui