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J. Chen,T. Sekiguchi,R. Xie,P. Ahmet,T. Chikyo,D. Yang,S. Ito , F. Yin
©2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Stud. I.D ：M9910218
Stud.：嚴國瑋
Prof.：戴子堯 副教授
高等物理冶金-期末報告

Abstract

Introduction

Experimental

Results and discussion

Conclusions

Recombination activity of small-angle grain boundaries (SA GBs) in
mc-Si by means of electron-beam-induced current technique.

In the as-grown mc-Si, the EBIC contrasts of special Ʃ and random
GBs were weak at both 300 and 100 K, whereas those of SA GBs
were weak (<3%) at 300 K and strong (30–40%) at 100 K.

In the contaminated mc-Si, SA GBs showed stronger EBIC contrast
than Ʃ and R GBs at 300 K.

It is indicated that SA GBs possess high density of shallow levels
and are easily contaminated with Fe compared to other GBs.

Multicrystalline silicon (mc-Si) is the most widely
used material for solar cells. The highest efficiency
of mc-Si solar cells has reached 19.8% (cell area 1
x1cm2) , but that of commercial mc-Si solar cells
(cell area 10 x10 cm2) is limited at 14–15% due to
the existence of defects and impurities, such as
grain boundaries (GBs), dislocations, and transition
metal contaminations
A high purity boron-doped mc-Si ingot (resistivity0.5–
1.0 Ω
1.
Intentional Fe contaminations were conducted at 800
and 1000 C, corresponding to light and heavy
contamination levels)
2.
After chemical etching by CP4 solution and rinsing
into FeCl3 solution.
3.
Samples were sent into a furnace, maintained at 800
or 1000 C for enough time and cooled in air (with a
cooling rate of 30 K/s)
4.
EBIC observation, by chemical polishing with CP4
solution, Schottky contacts were prepared by an
aluminum deposition with a thickness of 25 nm.

SE, EBSD and EBIC images of the Ʃ, R
and SA GBs in the as-grown mc-Si:
(a) SE; (b) EBSD; (c) EBIC_300 K and
(d) EBIC_100 K.
SA GBs are the most detrimental
defect in mc-Si since they exhibit
the strongest recombination
strength at 300 K, when they are
contaminated. The strong
impurity gettering ability of SA
GBs is also probably due to their
particular boundary structure.
Fig. 2. EBSD (a,b) and EBIC (c,d) images of the R, R, and SA GBs in the lightly (a,c)
and heavily (b,d) contaminated mc-Si. Temperature: 300 K.
Bright field TEM micrographs of the SA and R3 GB in the heavily contaminated mc-Si and R GB in
the as-grown mc-Si: (a) SA1; (b) SA3; (c)R3 and (d) R1.

The recombination activity of SA GBs in the asgrown and contaminated mc-Si was studied.

Bright field TEM micrographs of SA GBs in the asgrown mc-Si was weak at 300 K and strong at
100 K.

SA GBs act as strong recombination centers even
at 300 K in both the lightly and heavily Fe
contaminated mc-Si.
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