Transcript Surface Passivation of Crystalline Silicon Solar Cells: A Review

Surface Passivation of Crystalline
Silicon Solar Cells: A Review
Armin G. Aberle
Progress in Photovoltaics: Research and
Application 8,473-487,2000.
Outline




Introduction
Fundamental physics
Surface passivation method
Surface passivation of c-Si solar cells
2010/8/27
NCTU IEO GPL
2/5
Introduction

Defects
 Extrinsic (Processing related)
 Intrinsic (Si related, unavoidable)

Dangling bond
 Growth condition
 Dislocation
2010/8/27
NCTU IEO GPL
3/5
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
2010/8/27
NCTU IEO GPL
4/5
Surface recombination

Shockley-Read-Hall (SRH) theory
Surface
Recombination
rate:

Ec
Et
Ev
Low recombination rate strategy
 1. low surface state Nst
 2. low carrier concentration ns, ps
2010/8/27
NCTU IEO GPL
5/5
Reduction of the surface states

Growth/deposition of a dielectric film




SiO2

Al2O3
d 
SiNx
4n
Antireflective coating layer
Dielectric layer(d)
Si solar cell

Chemical methods
 HF immersion
 Alcoholic solution
2010/8/27
NCTU IEO GPL
6/5
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)
2010/8/27
NCTU IEO GPL
7/5
Combined passivaction
2010/8/27
NCTU IEO GPL
8/5
Concept
Al2O3
+
+
+
+
+
+
-
e-
h+


The fixed charge induced the negative charge on the surface,
bending the band diagram.
Al2O3 is suitable to p-type Si substrate.
2010/8/27
NCTU IEO GPL
9/5
PERL solar cells

Passivated Emitter and Rear Locally Diffused Solar Cell
(24.7%)
2010/8/27
NCTU IEO GPL
10/5
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.
2010/8/27
NCTU IEO GPL
11/5
Thanks for your attention!!