EE 237: Solar Energy Conversion Week 5: Light Trapping MJ solar ...

EE 237: Solar Energy Conversion

Week 5: Light Trapping

MJ solar cell April 29 2013 tanford University

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Most Standard Light Trapping Scheme

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Lambertian Surface

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Lambertian Surface

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Black silicon

http://en.wikipedia.org/wiki/Black_silicon tanford University

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Sunpower cell

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Optimal thickness of SiN ARC

http://pveducation.org/pvcdrom/design/anti-reflection-coatings tanford University

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Effect of Lambertian Light Trapping

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Optimal Solar Cell Thickness

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Material Thickness Tradeoff

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Benefits of Light Trapping

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Suggested Reading • Light trapping in crystalline silicon • HO5#: Eli, Cody paper • HO6#: Pyramid Texturing

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MJ solar cell 1. Key Features

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MJ solar cell

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Different Configuration

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How many terminals

Pros

Cons

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How many terminals

Pros: • 2 terminals only

Cons • Current matching • Lattice matched growth tanford University

• No current matching

• Individual load matching • Shading from metallization on each cell 17

Key Features 1 ARC

2

Window Layer

3 Back Surface Field

4 Tunnel Junction

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Key Features

1 ARC

SiN

Highest Eg

Medium Eg

Medium Eg Low Eg

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Key Features

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1 ARC

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Window Layer

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Window Layer

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BSF

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3 Back Surface Field

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Why Tunnel Junction ?

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4 Tunnel Junction

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Tunnel Junction

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4 Tunnel Junction

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Tunnel Junction

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4 Tunnel Junction

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MJ solar cell 2. Cell design 3. Issues

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Optimal Bandgaps (2 junction)

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Optimal Bandgaps (3 junction) Champion Cells Cylinder {1.86, 1.39, 0.67} Cone {1.80,1.29,0.67}

Sphere {1.83,1.34,0.89}

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3 junction: material options

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3 junction: InGaP / (In)GaAs / Ge

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Growth options

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More junctions the better ?

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Effect of spectrum Quiz: will this work well in space ?

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Effect of spectrum Quiz: will this work well in space ?

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Optimal Concentration

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Concentrators

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Concentrators

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Concentrators

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Concentrators

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Suggested Reading • III-V MJ solar cells • Handbook of Photovoltaics, Chapter 8 • http://bit.ly/XPtTQg • HO7#: Book chapter on III-V MJ solar cell • Concentrator design • Handbook of Photovoltaics, Chapter 10 • http://bit.ly/115DsyO

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