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Enhanced Si Passivation and PERC Solar Cell Efficiency by Atomic Layer Deposited Aluminum Oxide with Two-step Post Annealing
In this study, aluminum oxide (Al 2 O 3 ) films were prepared by a spatial atomic layer deposition using deionized water and trimethylaluminum, followed by oxygen (O 2 ), forming gas (FG), or two-step annealing. Minority carrier lifetime of the samples was measured by Sinton WCT-120. Field-effect pa...
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Published in: | Nanoscale research letters 2019-04, Vol.14 (1), p.139-10, Article 139 |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | In this study, aluminum oxide (Al
2
O
3
) films were prepared by a spatial atomic layer deposition using deionized water and trimethylaluminum, followed by oxygen (O
2
), forming gas (FG), or two-step annealing. Minority carrier lifetime of the samples was measured by Sinton WCT-120. Field-effect passivation and chemical passivation were evaluated by fixed oxide charge (
Q
f
) and interface defect density (
D
it
), respectively, using capacitance-voltage measurement. The results show that O
2
annealing gives a high
Q
f
of − 3.9 × 10
12
cm
−2
, whereas FG annealing leads to excellent Si interface hydrogenation with a low
D
it
of 3.7 × 10
11
eV
−1
cm
−2
. Based on the consideration of the best field-effect passivation brought by oxygen annealing and the best chemical passivation brought by forming gas, the two-step annealing process was optimized. It is verified that the Al
2
O
3
film annealed sequentially in oxygen and then in forming gas exhibits a high
Q
f
(2.4 × 10
12
cm
−2
) and a low
D
it
(3.1 × 10
11
eV
−1
cm
−2
), yielding the best minority carrier lifetime of 1097 μs. The SiN
x
/Al
2
O
3
passivation stack with two-step annealing has a lifetime of 2072 μs, close to the intrinsic lifetime limit. Finally, the passivated emitter and rear cell conversion efficiency was improved from 21.61% by using an industry annealing process to 21.97% by using the two-step annealing process. |
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ISSN: | 1931-7573 1556-276X |
DOI: | 10.1186/s11671-019-2969-z |