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Centre of Excellence for Advanced Silicon Photovoltaics and Photonics*

“Third Generation Photovoltaics”

Martin A. GreenUniversity of New South Wales

Sydney, Australia

* Supported by the Australian Research Council

Photovoltaics - Electricity from Sunlight UNSW

First Generation Wafers/Ribbons

Strengths. reliable, durable, etc.Weaknesses. material intensive. < US$1/Wp unlikely. energy payback only 4yrBUTzero energy if growth > 25%/yr(Lysen, PV in Europe)

Photovoltaics - Electricity from Sunlight UNSW

Second Generation (thin-film)

Crystalline Silicon on Glass (CSG)

Pacific Solar >> CSG Solarfirst products 2006

Metal

Resin

n+

Textured glass'Crater' 'Groove' 'Dimple'

Light In

p Siliconp+

Photovoltaics - Electricity from Sunlight UNSW

II. Efficiency/cost

II

100

80

60

20

0 100 200 300 400 500

US$0.50/W

US$1.00/W

US$3.50/W

Cost, US$/m2

US$0.10/W US$0.20/W

Present limit

Thermodynamiclimit

40

I

Effic

ienc

y,%

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Efficiency Limits

η≤ (1-TASs/Es) = 93.3% (direct) = 73.7% (global)

Tc .

ES

EC

.

Q

S = Q/TA

SG > 0

TA

SS

SC

W

. .

.

.

.

.

Photovoltaics - Electricity from Sunlight UNSW

III. Efficiency/cost

II

100

80

60

20

0 100 200 300 400 500

US$0.50/W

US$1.00/W

US$3.50/W

Cost, US$/m2

US$0.10/W US$0.20/W

Present limitIII

Thermodynamiclimit

40

I

Effic

ienc

y,%

Photovoltaics - Electricity from Sunlight UNSW

?

Third Generation

. thin-film

. high efficiency(> single junction)

. abundant materials

. non-toxic

. stable, durable

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Options/Limits100%

74%68%

54%49%44%39%31%

0%

58%

circulators

tandem (n )hot carrier

impurity PV & band, up-converterstandem (n = 3)thermal, thermoPV, thermionics

impact ionisationtandem (n = 2)down-converterssingle cell

tandem (n = 6)

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Hot Carrier Cells

Bandgap (eV)

cold carriers

0.0 0.5 1.0 1.5 2.0 2.5 3.0

80

60

40

20

0Ef

ficie

ncy

(%) 1

2hot carriers

InN Si

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Hot Carrier Cells quantum dot absorber

hole contactelectron contact

1. Energy relaxation: radiative ~ phonon

2. Energy selective contacts

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“Hot Phonons”/Phononic Bandgapstunnelingcontact

absorber

Silicon

InN

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Up-Conversion

1480 1500 1520 1540 1560 158018

20

22

24

26

28

λ (nm)

Abs

orpt

ion

(%)

1480 1500 1520 1540 1560 1580

0.2

0.4

0.6

0.8

1

1.2

EQE

(%)

EQE x~2000 QTH lamp excitationEQE Laser excitation

absorption 0.8mm EVA:phosphor [7:3]

Incident light

Solar cell

Insulator

ReflectorUp-Converter

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TandemsSolar cells

Decreasing band gap

Sunlight

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2D/3D Silicon

0

0.2

0.4

0.6

0.8

1

1.2

1 1.2 1.4 1.6 1.8 2

Photon energy [eV]

Pho

tolu

min

esce

nce

[a.u

.]0.6nm

1.0nm

1.1nm

1.7nm

Appl. Phys.Lett. 84, 2286,2004

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0D/3D Silicon

SiOx, SiyNx, SiCx

SiO2, SizN4, SiC

SiOx, SiyNx, SiCxSiO2, Si3N4, SiC

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Si Quantum Dot Tandem (SQOT)

CSG 1module

CSG 2module

CSG 3module

12.5%

18.1%

42.5%

16.3%18.2%20.2%

47.5%50.5%

Number of cells1 2 3

10

20

30

40

00

AM1.5G Efficiency

Si bottom cellFree choice

29%33%

45%

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All-Si CSG Tandem

MetalResinp+

n+

Light In

p+pn+

p

Textured glass'Crater' 'Groove' 'Dimple'

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Conclusions. innovation needed for PV to reach full potential

. hot carrier:resonant tunneling, phononic engineering

. multiple step:rear up-converter

. tandems:all c-Si quantum dot tandems (SQOTs)