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The University of New South Wales

Development and Optimization ofLaser-Doped Solar Cells

Ziv Hameiri

13/6/2012

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Contents

Introduction

Laser doping

Optimization:

Laser-Induced Defects in Laser-Doped Solar Cells

Influence of Metallisation Methods

Influence of Laser Power on Laser-Doped Solar Cells

Conclusions

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Introduction

In order to make solar energy cost-competitive withother sources of energy (i.e. fossil fuels), reduction ofthe PV system cost is essential

One path to reduce the cost is to reduce the raw

material cost, by reducing the amount of silicon used fora wafer or by employing a lower quality of silicon, whichis cheaper to produce

The second path is increasing the solar systemefficiency without significantly increasing themanufacturing cost

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Introduction

Solar technologies market report, NREL, 2008

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Introduction

However, standard industrial solar cell efficiency is in the16-18% range

Main limitations of the high-efficiency structure:

Very expensive

Very long fabrication process

small output(five different photo-lithographic processes, eight high temp.processes!)

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Introduction

Selective emitter

Local back-surface-field

Rear surface passivationAluminum back-surface-field

Green MA. Silicon Solar Cells: Advanced Principles & Practice, 1995

PERLStandard solar cell

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Introduction

The Aim:

To develop an industrial version of the high-efficiency solar cell structure

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IntroductionSelective Emitter SC

Main limitation:A long high-temperature process is required to create theselective emitter.

[2-7]

The buried-contacts solar cell

(UNSW)

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Laser Doping

Creation of selective emitter without additional hightemperature process

1968: Fairfield and Schwuttke laser doped diode

Laser-induced diffusion: Diffusion in the liquid phase

Different dopant sources in gas, liquid and solid states

Fairfield J, Schwuttke GH. Solid State Electronics1968; 11: 1175-1176

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Laser Doping

Dopant

source

Dielectriclayern++ n++ n++

Not to scale

p-type wafer Emitter

Al BSF

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Influence of Laser Power

.

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Influence of Laser Power

.

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OPTIMIZATION OF LDSE SOLAR CELLS

LASER INDUCED DEFECTS

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Laser-Induced Defects

.

Bare Samples

SiNx Sample

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Laser-Induced Defects

.

Bare Sample SiNX Sample

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SON Sample

Laser-Induced Defects

.

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Laser-Induced Defects

Solar Cell Results:

.

Defect density can be reduced by adding a thin SiO2 layer

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OPTIMIZATION OF LDSE SOLAR CELLS

PLATING METHOD

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Influence of Metallisation Methods

.

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Influence of Metallisation Methods

.

Dark I-V curve:

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Influence of Metallisation Methods

Conclusions:

Higher p-FFs were achieved for photoplated laser-dopedsolar cells

p-FF is almost independent of laser diode current ifphotoplating is combined with a well-optimised Ni sintering

In this case the solar cell is not limited by shunts

.

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INFLUENCE OF LASER POWER

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Influence of Laser Power on Solar cells

Solar Cells:

.

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Influence of Laser Power on Solar cells

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Conclusions

Selective emitter solar cell structure was developed,based on laser doping

The laser doping method offers significant control onthe junction parameters (sheet resistivity and junction

depth) The dielectric layer and the plating method have a large

impact on the solar cell performance

Efficiency of 18.7% was achieved on commercial CZ

wafers

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Laser-Induced Defects

.

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The School of Photovoltaic and Renewable Energy Engineering

THANK YOU

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The School of Photovoltaic and Renewable Energy Engineering

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