Thin-Film PV Technologies III-V PV Technology Week 5.1 Arno Smets - - PowerPoint PPT Presentation

Arno Smets

Thin-Film PV Technologies

III-V PV Technology

Week 5.1

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(Source: NASA)

III – V PV Technology

Semiconductor Materials

III-V semiconductors: GaAs: GaP: InP: InAs: GaInAs: GaInP: AlGaInAs: AlGaInP:

Atomic Structure Silicon GaAs

Lattice constant: 0.543 nm Atom density: 5.01022 cm-3 Density: 2.33 gcm-3 Lattice constant: 0.565 nm Atom density: 4.421022 cm-3 Density: 5.32 gcm-3 Lattice constant Lattice constant

Ex <100> <111> EL L-valley Wave vector Heavy holes

Eg = 1.42 eV EL = 1.71 eV EX = 1.90 eV E90 = 0.34 eV

X-valley

Energy

Eg G-valley

T = 300K

Absorption coefficient

107 106 105 104 103 102 101 100 200

GaAs InP Germanium Silicon

Absorption coefficient, a (cm-1)

400 600 800 1000 1200 1400 1600 1800 2000

Wavelength, l (nm)

Charge Carrier Recombination

Radiative Auger SRH

75 50 25

Bandgap (eV)

Spectral Mismatch

Percentage of incident light energy

1 3 2 100

Usable electric power Below-bandgap photons Relaxation to band edges Other losses

Multijunction

“Excess energy” V C “Excess energy” V C

III-V Technologies

AR n+-GaAs n-AllnP n-GalnP n-GalnP p-AlGalnP p++-tunnel junc. n++-tunnel junc. Middle Cell Window n-GaAs p-GaAs p-GalnP p++-tunnel junc. n++-tunnel junc. buffer nucleation n-Ge p-Ge substrate contact Contact=

Top cell window/emitter Top cell base/BSF Wide-Eg tunnel junction Middle cell window/emitter Middle cell base/BSF TC & MC crystal quality: Nucleation, buffer, Interface control, Lattice-matching

Courtesy: Richard King Spectro Labs

III-V Technologies

AR n+-GaAs n-AllnP n-GalnP n-GalnP p-AlGalnP p++-tunnel junc. n++-tunnel junc. Middle Cell Window n-GaAs p-GaAs p-GalnP p++-tunnel junc. n++-tunnel junc. buffer nucleation n-Ge p-Ge substrate contact Contact=

Top cell window/emitter Top cell base/BSF Wide-Eg tunnel junction Middle cell window/emitter Middle cell base/BSF TC & MC crystal quality: Nucleation, buffer, Interface control, Lattice-matching

Courtesy: Richard King Spectro Labs

III-V Technologies

AR n+-GaAs n-AllnP n-GalnP n-GalnP p-AlGalnP p++-tunnel junc. n++-tunnel junc. Middle Cell Window n-GaAs p-GaAs p-GalnP p++-tunnel junc. n++-tunnel junc. buffer nucleation n-Ge p-Ge substrate contact Contact=

Top cell window/emitter Top cell base/BSF Wide-Eg tunnel junction Middle cell window/emitter Middle cell base/BSF TC & MC crystal quality: Nucleation, buffer, Interface control, Lattice-matching

Courtesy: Richard King Spectro Labs

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 15

J (mA/cm2) Voltage (V)

Single junctions

3 2 1 3 2 1

? ? ?

Window side

Multi-junction approach

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 15

J (mA/cm2) Voltage (V)

Single junctions

3 2 1 3 2 1

Multi-junction approach

1 2 3

Window side

Multi-junction approach

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 15

J (mA/cm2) Voltage (V)

Single junctions

3 2 1 3 2 1

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 30 15 25 20

Voltage (V)

Multi-junctions

5 10 30 15 25 20

?

J (mA/cm2)

Equivalent circuit - ideal solar cell

ID IPH I VOC,1 + _

ID IP

H

I

+ _

ID IP

H

I

+ _

ID IP

H

I

VOC,3

+ _ + _ + _

ID IP

H

I

+ _

ID IP

H

I

+ _

ID IP

H

I

+ _ + _

JSC,1

+ _

Series

• r

parallel?

+ + VOC,3 VOC,2 VOC,1 + + JSC,1 JSC,2 JSC,3

VOC,2 VOC,1 JSC,2 JSC,3

ID IP

H

I

+ _

ID IP

H

I

+ _

ID IP

H

I

VOC,3

+ _ + _ + _

ID IP

H

I

+ _

ID IP

H

I

+ _

ID IP

H

I

+ _ + _

JSC,1

+ _

Series

• r

parallel?

+ + VOC,3 VOC,2 VOC,1 + + JSC,1 JSC,2 JSC,3

VOC,2 VOC,1 JSC,2 JSC,3

Multi-junction approach

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 15

J (mA/cm2) Voltage (V)

Single junctions

3 2 1 3 2 1

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 30 15 25 20

Voltage (V)

Multi-junctions

5 10 30 15 25 20

?

J (mA/cm2)

Multi-junction approach

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 5 10 15

J (mA/cm2) Voltage (V)

Single junctions

3 2 1 3 2

0.0 0.2 0.4 0.6 0.8 1.0 1.4 1.6 1.8 2.0 2.2 2.4 5 10 30 15 25 20

Voltage (V)

Multi-junctions

5 10 30 15 25 20

3 2 1 1+2+3 1 J (mA/cm2)

Triple Junction p n p n p n

p n p n p n

= =

Triple Junction p n p n p n

Epitaxy of III-V Materials

Crystalline growth induced by a crystalline substrate

Source: http://www.photonics.ethz.ch/research/core_competences/technology/

Epitaxy of III-V Materials

Epitaxy of III-V Materials

Source: http://www.photonics.ethz.ch/research/core_competences/technology/

Bandgap vs. Lattice constant

4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 4.5 5.0 5.5 6.0 6.5 GaN BP BAs InN Si Ge InAs GaSb

Bandgap (eV)

ZnS MgSe ZnSc AlP CdS AlSb CdTe CdSe InP GaAs GaP ZnFe InSb AlAs

Lattice Constant (Å)

Crystal mismatch: interface defects

E.F E.F. Schubert

Light-Emitting Diodes (Cambridge Univ. Press) www.LightEmittingDiodes.org

Bandgap vs. Lattice constant

4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 4.5 5.0 5.5 6.0 6.5 GaN BP BAs InN Si

Ge

InAs GaSb

Bandgap (eV)

ZnS MgSe ZnSc AlP CdS AlSb CdTe CdSe

InP GaAs GaP

ZnFe InSb AlAs

Lattice Constant (Å)

Spectrolab

JSC = 17.76 mA/cm2 VOC = 2.633 V FF = 0.85 AM 0 conditions

EQE spectrum of multijunction cells

MH Tsutagawa et al. 34th IEEE PVSC pp. 1959 (2009)

http://www.ise.fraunhofer.de/en/press-and-media/press-

releases/presseinformationen-2013/43.6-four-junction-solar-cell- under-concentrated-sunlight

EQE spectrum of 4-junction cells

Lattice Matched and Metamorphic 3-Junction Cell Cross-Section

Wide-bandgap tunnel junction

AR n+-GaAs n-AllnP n-GalnP n-GalnP p-AlGalnP BSF p++-tunnel junc. n++-tunnel junc. n-Ga(In)P window n-Ga(In)As emitter p-Ga(In)As base p-GalnP BSF p++-tunnel junc. n++-tunnel junc. N-Ga(In)As buffer nucleation n-Ge p-Ge substrate contact Contact

GaIP top cell Ge(In)As middle cell Buffer region Ge bottom cell

Tunnel junction

AR n+-GaAs n-AllnP n-GalnP n-GalnP p-AlGalnP BSF p++-tunnel junc. n++-tunnel junc. n-Ga(In)P window n-Ga(In)As emitter p-Ga(In)As base p-GalnP BSF Contact p++-tunnel junc. n++-tunnel junc. N-Ga(In)As buffer nucleation n-Ge p-Ge substrate contact

Courtesy: Richard King Spectro Labs

III – V PV Technology

Thank you for your attention!