Surface Passivation of Crystalline Silicon Solar Cells: A Review

Armin G. Aberle

Progress in Photovoltaics: Research and Application 8,473-487,2000.

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Outline

Introduction Fundamental physics Surface passivation method Surface passivation of c-Si solar cells

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Introduction

Defects Extrinsic (Processing related) Intrinsic (Si related, unavoidable)

Dangling bond Growth condition Dislocation

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Surface type in Si solar cell

Metalized Finger and bus bar Very high surface recombination Avoid recombination loss

Non-metalized Illuminated region Well passivated and good blue response Avoid highly doped

Back electrode high surface recombination Avoid recombination loss

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Surface recombination

Shockley-Read-Hall (SRH) theory

Low recombination rate strategy 1. low surface state Nst

2. low carrier concentration ns, ps

Et

Ec

Ev

SurfaceRecombination rate:

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Reduction of the surface states

Growth/deposition of a dielectric film SiO2

Al2O3

SiNx

Antireflective coating layer

Chemical methods HF immersion Alcoholic solution

Si solar cell

Dielectric layer(d)

nd

4

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Field-effect passivated

High-low junction p+-p n+-n Back surface field (BSF) Front surface field (FSF)

p-n junction MIS Selective emitter HIT(a-Si)

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Combined passivaction

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Concept

The fixed charge induced the negative charge on the surface, bending the band diagram.

Al2O3 is suitable to p-type Si substrate.

Al2O3

++++++

------

e-

h+

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PERL solar cells

Passivated Emitter and Rear Locally Diffused Solar Cell (24.7%)

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Band offset measurement

The Si substrate can passivated by dielectric film and electric field effect method.

The Al2O3 is suitable for p-type Si substrate passivation, and the SiNx is suitable for n-type Si substrate passivation.

Thanks for your attention!!