Surface passivation of c-Si for silicon heterojunction solar cells using high-pressure hydrogen diluted plasmas

Dimitrios Deligiannis,Arno H M Smets,Ravi Vasudevan,Miro Zeman,René A C M M Van Swaaij

doi:10.1063/1.4931821

Dimitrios Deligiannis, Arno H M Smets + Show 3 more

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https://doi.org/10.1063/1.4931821

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Abstract

In this work we demonstrate excellent c-Si surface passivation by depositing a-Si:H in the high-pressure and high hydrogen dilution regime. By using high hydrogen dilution of the precursor gases during deposition the hydrogen content of the layers is sufficiently increased, while the void fraction is reduced, resulting in dense material. Results show a strong dependence of the lifetime on the substrate temperature and a weaker dependence on the hydrogen dilution. After applying a post-deposition annealing step on the samples equilibration of the lifetime occurs independent of the initial nanostructure.

Highlights

Improving surface passivation is an important aspect for so-called Silicon Heterojunction (SHJ) solar cells
The amorphous silicon (a-Si):H residue is fitted with four Gaussian peaks at 180, 330, 440 and 480 cm−1 representing the acoustic and optical phonon modes that contribute to the a-Si:H Raman signal.[24,26]
The high hydrogen dilution and high-pressure regime is proposed for the passivation of crystalline silicon (c-Si) with a-Si:H

Summary

INTRODUCTION

Improving surface passivation is an important aspect for so-called Silicon Heterojunction (SHJ) solar cells. At the same time the deposition conditions determine the hydrogen content of the layer.[13] It has been shown that hydrogen is essential for the passivation,[14] as is reflected in the Voc of SHJ devices.[5] For this purpose H2 plasma treatments during[15] and post-deposition[16,17] have been proposed achieving state-of-the-art passivation In both cases hydrogen incorporation led to a significant improvement in passivation, while attempts to apply pre-deposition hydrogen treatment on the substrate resulted in the creation of defects on the c-Si surface and proved detrimental for the passivation.[18] At the same time it has been shown that such attempts to increase the hydrogen content and improve the passivation quality can significantly alter the nanostructure of a-Si:H leading to void-rich material and in some cases cause irreversible damage at the interface.[19]. In this work we study the nature of the defect reduction passivation mechanism using a-Si:H passivating layers processed at high-pressure and high hydrogen dilution ratios

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION