Nanowires for PV and BIPV

Martin MagnussonNanoLund / Solid State PhysicsLund University

PV technology generations

CPV

Shockley–Queisser limit

W. Shockley and H. J. Queisser, “Detailed Balance Limit of Efficiency of p-n Junction Solar Cells”, J Appl Phys 32, 510 (1961)

“Thermodynamics”

“Transparent”“Heat”

Top competing technologiesTechnology Lab

efficiency Module efficiency Approximatemarket share Main player

Polycrystalline Si 21,9 % 11 – 16 % 70 % China

Single crystalline Si 25.0 % 14 – 18 % 16 % Sanyo, Panasonic

High-end Si 26,7 % 21 % 8 % SunPower

Poly-CdTe 21,0 % 16 % 4 % First Solar

Poly-CuInGaSe 21,7 % 13 % 2 % Nanosolar

Concentrator III–V tandem 46 % 38,9 % 0,1 % Soitec

Lift-off thin film GaAs 28,8 % ? - Alta Devices

Nanowire III–V 15,3 % ? - Sol Voltaics IIIII

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CPV

Why III–V nanowire solar cells?

• Great potential to offer high efficiency conversion

–InP NW solar cell with η = 13.8%

–World record GaAs NW solar cell device with η =15.3%

• Great potential to offer reduced cost for III–Vs

–Peel off and substrate re-use

–AerotaxyJ. Wallentin et al.Science 339, 1057 (2013)

InP

I. Åberg et al.IEEE J PV PP:99 1–6 (2015)

15.3 % efficiency

GaAs

t=2000 nm

Anttu & Xu, Optics Express, 2013

Modelling of ideal structures

NANO-TANDEM project

What is BIPV?

• Building Integrated Photovoltaics• Solar cells integrated in building

elements• Rather than just mounting solar

panels on buildings• Fundamentally the same as

“normal” PV

Why (not) BIPV?

• Advantages:• Use building area more

efficiently• Dense cities have no

room for solar farms• Ideally cover windows as

well – (semi)transparent PV

• Reduce cost (?) due to simpler construction

• Aesthetics

• Disadvantages• Not standard products• Durability/maintenance?• Not relevant for large

scale solar power

NW BIPV advantages

Nanowires Silicon

Free form factor Films simple to cut into shapes

Can be shaped, but produces waste

Curved cells Films are flexible Not flexible

Transparency Can be optimized for transparency Absorbs visible light

Transparent NWPV?

• More free parameters for NW solar cells:• Material bandgap – optimize for IR absorption• Wire dimensions (length, width) – optimize for IR• Wire spacing – optimize to transmit (some) visible

light

• UV solar cells?• In principle possible to make InGaN-based NWPV• Optimized for blue/UV absorption• Use in tandem with IR NWPV

Lunds universitet / LTH / Fysiska institutionen / Martin Magnusson

Nanowires are great …

Lunds universitet / LTH / Fysiska institutionen / Martin Magnusson

Lunds universitet / LTH / Fysiska institutionen / Martin Magnusson Image: wikimedia commons / Rogeriopfm

2018-05-23Image: www.murdoch.edu.au

2018-05-23

… and we need a lot of them!

Image: Serpa Solar Power Plant (Wikipedia)

2018-05-23

Mass production of nanowires?• Nanowires are normally grown by MOVPE• Batch process, cycle time min 30 min (today 2 h)• Largest machine can handle a few 30 cm wafers• Wires typically grow 1–10 nm/second• Currently not an alternative for large surfaces

Animation by Magnus Heurlin

2018-05-23

Aerotaxy: nanowire growth

Heurlin et al., ”Continuous gas-phase synthesis of nanowires with tunable properties” Nature 492, 90 (2012)

Growth rate 1 µm/second

Gold particles

Size selection

Collect wires

Precursors

(TMGa and AsH3)

2018-05-23

Sol Voltaics technology

1 mm

Nanowire film formation Cell Integration

I Åberg et al., ”A GaAs Nanowire Array Solar Cell With 15.3% Efficiency at 1 Sun” IEEE J Photovolt6 185 (2016)

15.3 % efficiency

Interest?

• LU, Sol Voltaics, Fraunhofer ISE already working on NWPV in Nano-Tandem project• No explicit BIPV part

• Interested to pursue BIPV if there is funding• And especially if there are partners

• Realism?• NWPV is still R&D• BIPV is not fundamentally different, although NWPV has

potential

2018-05-23

Thanks for your attention!

Illustration © Sol Voltaics AB