si nano wire based solar cells

7/27/2019 Si Nano Wire Based Solar Cells

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Solar Cell

Nanowire

Silicon Nanowires

efficiency table

Si Nanowire Solar cells

Challenges

Gratitude

Si NANOWIRE BASED SOLAR CELLS

Nanowire solar cell
http://find/


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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

What is a solar cell

Solar Cells Everywhere

Energy Conversion

Planar Solar cells


Cell is thin Si

waferSize 10x10 cm :

size of a CD

Thickness is in

fractions of mmmetal pattern is

to make electrical

contacts.

ROSLIN Nanowire solar cell
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude



Energy Conversion

Planar Solar cells

Solar Cells:

SafeClean

Durable

Reliable

QuietInstallable anywhere

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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude



Energy Conversion

Planar Solar cells

Energy Conversion in Solar cell

Light is shone

Electrons are knockedout

Electrons and holes

move in opposite

directionsElectrical output is

generated between the

contacts

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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude



Energy Conversion

Planar Solar cells

Planar Silicon Solar Cells:

Thickness for an efficient light absorption.

High purity to avoid recombining.

High Reflectance.

High Recombination Rate.


S l C ll
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude



Energy Conversion

Planar Solar cells

Sliced into nano-scale

Diameters from 1 to 50nmNano scale Silicon has a color difference

Nano sized Silicon shows:

Physical propertiesOptical properties

Electronics properties changeElectrons occupy different energy levels


S l C ll
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Nanowire


Solar Cell
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Nanowire-Properties

No Lattice Mismatch.

Flexibility to create heterostructures.

Broad range of materials.

integration of compound semiconductor based

optoelectronic devices with silicon based microelectronics.


Solar Cell
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Properties

Si Nanowires-Properties

Light Trapping:

Light falling on the substrate gets reflected and once again gets

absorbed by silicon nanowires.


Solar Cell


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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Properties

Si nanowire-Properties

Increased Surface Area:

Very narrow pointed structures.

Diameter in nanometers.

Length in micrometers.

Greater area made of p-n junctions is exposed to sunlight.Increases absorptivity.


Solar Cell
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Properties

Si nanowire-Properties

Reduced Size

Increased absorptivity

Reduced Reflectivity

Efficient electron transport

Reduced recombination


Solar Cell
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Solar Cell

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Efficiencies


Solar CellS l C ll Th
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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Theory

Fabrication

Patterned Chemical Etching



Benefits

Vision


Solar CellSolar Cell Theory


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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Theory

Fabrication




Benefits

Nanowire Solar Cell-Theory




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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Theory

Fabrication




Benefits

The energy levels of the valence and conduction bands(HOMO and LUMO levels for the polymer)aligned such that

electrons can be collected at one electrode and holes at

the other.


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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Theory

Fabrication




Benefits

Fabrication:VLS Growth of Nanowires


Solar Cell

N iSolar Cell Theory


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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Solar Cell Theory

Fabrication




Benefits

Doping in Nanowires:

Use of a catalyst that by itself causes doping.

Adding dopants to the catalyst so that dopant atoms will be

released and incorporated into the nanowires during

growth.Supplying dopant in the form of gaseous precursor while

CVD growth. Better controllability and widely used for Si.

After doping, thermal treatment required for activation.

Junction Formation:

The shell or p-n junction in SiNW can be formed by,

Diffusion of opposite dopants. But if temperature is high or

time is long, doping of the entire nanowire can get

reversed.

Thin-film deposition of opposite carrier type. Also used forheterojunction formation.ROSLIN Nanowire solar cell

Solar Cell

N iSolar Cell Theory
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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

y

Fabrication




Benefits


Dip coat n-type Si wafer inaqueous silica bead solution

Formation of a closelypacked mono-layer


Solar Cell

NanowireSolar Cell Theory


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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

y

Fabrication




Benefits

Deep Reactive Ion Etching

using the beads as etchmask to form nanowires

Bead removal in HF and

Boron diffusion to form theradial p-n junction


Solar Cell

NanowireSolar Cell Theory
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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Fabrication




Benefits



Solar CellNanowire

Solar Cell Theory
http://find/


21/26

Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Fabrication




Benefits

Features of Fabricated Device

NW Core Diameter: 80-100 nm.

Shell Thickness: 400 nm.Shell layer thick enough to completely cover the core;

Reduces sheet resistance.

Shell doping higher; Depletion region expected mainly in

crystalline NW core.Average wire density: 2*1018/cm2.


Solar CellNanowire

Solar Cell Theory
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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Fabrication




Benefits

Fabrication Details

Substrate Cleaning

NW Growth

Shell Growth

Contact


Solar CellNanowire

Solar Cell Theory

F b i i
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Nanowire

Silicon Nanowires

efficiency table


Challenges

Gratitude

Fabrication




Benefits

Benefits of nanowire geometry


Solar CellNanowire

Solar Cell Theory

F b i ti
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Silicon Nanowires

efficiency table


Challenges

Gratitude

Fabrication




Benefits

Radial charge separation increases defect tolerance for

radial junction.Natural anti reflective structure; Enhanced light

trapping&absorption.

Relaxed inter-facial strain.

Single-crystalline synthesis on non-epitaxial substrates.


Solar CellNanowire


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Silicon Nanowires

efficiency table


Challenges

Gratitude

Remaining Challenges And Future Outlook

Solar cells are less expensive and use fewer natural

resources.

The radial junction nanowire geometry,opening up thepossibility to use a small amount of

abundant,nontoxic,low-cost material to make solar cells

with performance close to that of current planar technology.

The ability to make single-crystalline nanowires on low-cost

substrates such as aluminum foil and to relax strain in

subsequent epitaxial layers removes two more major cost

hurdles associated with high-efficiency planar solar cells.


Solar CellNanowire
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Silicon Nanowires

efficiency table


Challenges

Gratitude

THANK YOU

Mr.VINOD G.

Mr.HARIKRISHNAN A.I.

http://find/

si nano wire based solar cells

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