future generation solid-state energy conversion

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Department of Electrical & Computer Engineering

kmontgomery.net

[email protected]

@KyleMontgomery0

Future Generation Solid-State Energy Conversion

Kyle Montgomery

May 12, 2014

http://www.kmontgomery.net/

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About Me

To 2000 In the beginning…

2004 Bachelor’s

2004-2007 Professional

2008 Master’s

2012 PhD

Present Research & Lecturer

Intern

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InfluencesJerry WoodallDistinguished Professor, UC DavisNAE Member, National Medal of TechnologyCompound Semiconductor Materials & Devices

David WiltTech Lead, Air Force Research Lab, Space VehiclesFormer Lead PV Engineer at NASASpace Photovoltaics, III-V MOVPE

Mark LundstromDistinguished Professor, PurdueNAE MemberElectron Transport and Device Modeling

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Overview

Motivation• The Energy Dilemma• Opportunities

Research• Photovoltaics• Future Directions

Teaching• Experience: Purdue & UC Davis• Future Directions

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Overview




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The Energy Dilemma (1/2)

1. We use too much energy

EIA, International Energy Outlook 2013

Total Global Energy Total Energy by Country

OECD: Organization for Economic Cooperation and Development

+60%

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The Energy Dilemma (2/2)

2. We waste too much energy

Conversion Loss (62%)Coal (41%)

Natural Gas (25%)

Nuclear (21%)

Renewables (12%)Residential (12%)

Commercial (12%)Industrial (9%)

Mostly Waste Heat

US EIA, Monthly Energy Review (January 2014)

Opportunity: Solar Resource

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Covering US~20M TWh / yr

2011 US Electricity Consumption 4100 TWh

Equiv. Land Area ~2000 km2 ½ the size of Rhode Island

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Wide Bandgap Cells for Multijunctions

K. Montgomery, PhD Thesis, 2012

Eg > 2 eV

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Opportunity: Lighting Efficiency

17% Percentage of total residential & commercial electricity used for lighting in US (EIA, 2011)

Efficacy [lm / W]US DoE, Solid-State Lighting Technology Fact Sheet, PNNL-SA-94206, March 2013.

Incandescent

Halogen

Compact Fluorescent

Linear Fluorescent

High Intensity Discharge (HID)

Light Emitting Diode (LED)

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Better Ways for Solid State Lighting

Current Technology:Low Cost, Decent Quality

Ideal Technology:High Cost, Superior Quality

NEED:True Green LED

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Overview




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Research Contributions

• Reviving Liquid Phase Epitaxy• GaP Solar Cells

– 2x improvement in spectral response• AlGaAs Solar Cells

– Enhanced Luminescence Near Crossover– Towards Dual Junction Integration on Si

• III-V / II-VI Digital Alloys• Integration to Novel Energy Conversion

Systems

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Semiconductor Menu

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Liquid Phase Epitaxy – Rotating Chamber

K. Montgomery, PhD Thesis, 2012

Benefits:• Perfected Crystal Structure• Better Stoichiometry• High Growth Rates• Economical

Challenges:• Stable Growth Conditions• Low Supersaturation

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GaP Solar Cells

C. R. Allen, et al., Sol. Energ. Mat. Sol. C., 94, 865 (2010).

Voltage (V)

Wavelength (nm)

Cur

rent

Den

sity

(mA

/cm

2 )In

tern

al Q

E

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Gettering in GaP

K. Montgomery, et. al., JEM, 40, 1457-1460 (2011).

Al-Ga @ 975°C

O-

Liquid

Solid

Ga

Al

GaP Substrate

AlGaP

Mol

e Fr

actio

n Al

Mole Fraction P P

Mole Fraction Ga

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Gettering Yields Higher Response

K. Montgomery, et. al., JEM, 40, 1457-1460 (2011).

Zn-O

Zn-S

Exciton

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AlGaAs Solar Cells by LPE

X. Zhao et.al, PVSC 40 (2014), K. Montgomery, et. al., EMC (2012)

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Non-Isovalent Alloys

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ZnSe-GaAs Digital Alloy

• Superlattice Miniband formation• Potential problem: intermediary

compounds at interfaces

S. Agarwal, K. H. Montgomery, et. al., Electrochemical and Solid-State Letters, 13, H5 (2010).

Effective Band Gap

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Wide Bandgap Cells for Hybrid PV-PT

• Goal: Maximize solar energy conversion using PV + Heat

• Benefit: Direct heat absorption allows for storage

K. Montgomery, et. al., PVSC 39 (2013) & Manuscript in Preparation

System Efficiency (@100x)

Tem

pera

ture

(°C

)

PV Bandgap (eV)

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Future Directions

Wide Bandgap Solar Cells Engineered Superstrates

Non-Isovalent Semiconductors

• Gettered Devices• Integrated Nanostructures• Tandem Integration

• Hybrid Epitaxy• III-V on Si• Polycrystalline III-V

• ZnSe-GaAs Epitaxy• Growth & Doping• Heterojunction Devices

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Overview




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Teaching Experience: Purdue

• Teaching Assistant– 2 semesters: Grad Level Microfabrication

• Lessons Learned– Textbook Knowledge ≠ Fab Skills– Laboratory Safety

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Teaching Experience: UC Davis• Lecturer

– Undergrad Circuits Analysis– ~200 students

• Lessons Learned (& still learning!)– Minimize loss in translation– Emphasize fundamentals, Expose details

kmontgomery.net/eng17

“…not only does he go on to teach us what we need to know to get by in circuits, he is a compelling lecturer, caring person, and above all he is able to deal with classroom issues with grace.”

http://www.kmontgomery.net/eng17

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Mentorship: UC Davis

PhD Students Undergraduates

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Teaching Plans: Graduate

• Materials Science for Microsystems Engineering• Microelectronics I• Proposed Course

Solid-State Energy Conversion Materials & Devices

REVIEW: Solid-State Physics, Material Properties, Thermodynamics

Photovoltaics Light Emitting Diodes Thermoelectrics Piezoelectrics

“Direct Energy Conversion” by Angrist (w/supplements)

Emphasis on Recent Research

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Teaching Plans: Undergraduate

• Circuits I-II• (Adv.) Semiconductor Devices• MATLAB Programming• Clean and Renewable Energy Systems

and Sources

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Overview




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Acknowledgements

Purdue UniversityProf. Mark Lundstrom, ECEProf. David Janes, ECEProf. Peide Ye, ECEProf. Eric Kvam, MSEProf. Peter Bermel, ECEProf. Gerhard Klimeck, ECEProf. Anant Ramdas, PhysicsDionisis Berdebes, ECEDr. Jayprakash Bhosale, Physics

Yale UniversityProf. Minjoo Larry Lee, EE

UC DavisProf. Jerry Woodall, ECEProf. Saif Islam, ECEProf. Subhash Mahajan, CHMSXin Zhao, ECE

UCLADr. Paul Simmonds

Air Force Research LaboratoryDavid WiltDr. Alex HowardJohn Merrill

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kmontgomery.net

[email protected]

@KyleMontgomery0

Thank you!

Any questions?


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kmontgomery.net

[email protected]

@KyleMontgomery0

Supplemental


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ZnSe-GaAs Physical Alloy

• Miscibility previously demonstrated

• N-type conductivity generally found

• Lack of prior work due to difficulty in suitable deposition technique

W. M. Yim, JAP, 40, 2617–2623, 1969.

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SiC Solar Cells150 suns

R. P. Raffaelle et. al., 28th PVSC, 2000, pp. 1257–1260.

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AlGaAs Growth by LPE

K. Montgomery, et. al., EMC (2012)

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InGaN Solar Cells Full Spectrum Coverage

Phase separationInGaN (37% In)

Jampana, et al., Electron Devic. Lett., 31, 32 (2010).R. Singh and D. Doppalapudi, Appl. Phys. Lett., 70, 1089 (1997).

DefectsInGaN (16.8% In,

2.67 eV)

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2.19 eV GaInP w/GaAsP Buffers on GaP

S. Tomasulo, et. al., PVSC 39, 2013.

In0.26Ga0.74P

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Wide Bandgap Cells for High-T

G. A. Landis, et. al., “High-Temperature Solar Cell Development,” NASA, 2004.

Temperatures up to 450°C

1.0 2.0 3.0 Bandgap

Effic

ienc

y20

10

27°C

900°C

AM0 (FF = 0.80, Pin = 1366.1 W/cm2)

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Engineered Superstrates

• Superstrate: Substrate templated with a heterogeneous material

• III-V on Si– Needs thick buffer layers– Problem: Dislocation densities

• LPE may help (w/MOCVD)

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

2

4

6

8

10

12

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Voltage [V]

Cur

rent

Den

sity

[mA

/cm

2]

Al0.23Ga0.77As(Eg ~ 1.75 eV)

Voc = 771 mVJsc = 13.8 mA/cm2FF = 63.4%Efficiency = 6.8%

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Primary Photovoltaic TechnologiesLow Cost, Low Efficiency

η ~ 6-22% η ~ 28-39% (at xx suns)

High Cost, High Efficiency

First Solar SolFocus

future generation solid-state energy conversion

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