From Silicon to Germanium Nanowires : growth processes and solar cell structures

Abstract : This thesis is dedicated to develop new solar cell architectures based on nanowires produced by a plasma-assisted Vapor Liquid Solid process. By optical modeling, detailed field and absorption profiles in the NW solar cells have been obtained and a 14 mA/cm2 matched photocurrent has been achieved for a-Si:H/µc-Si:H tandem solar cells. An electrical model for radial PN junction NW solar cells has also been developed from first principle rules, allowing a good understanding of the carrier transport. By analyzing step by step the SiNWs growth in a PECVD system we could propose a detailed explanation for the strong evolution of the NW density, morphology and crystallinity during growth. The rare hexagonal phase of Si has been observed in the as grown SiNWs with diameters smaller than 10 nm. For the first of time, we have provided TEM characterizations from [11-20] direction to give a clear proof of the hexagonal Si phase in as grown SiNWs. To develop low band bap, high mobility material for multi junction NW solar cells, we added germane to silane during the plasma-assisted VLS growth process. Ge contents from 0 to 100% have been achieved with Sn, In and Cu catalysts. We have found that above a critical temperature (~ 350 °C), micrometer long cylindrical Ge NWs can be obtained. NW based PIN radial junction solar cells having a-Si:H, a-SiGe:H and µc-Si:H as intrinsic absorber layers have been fabricated. For the SiGeNWs based solar cells, a 6% energy conversion efficiency has been achieved with p-i-n configuration. To our knowledge, this is the first demonstration of SiGeNWs based photovoltaic device.
Complete list of metadatas

https://pastel.archives-ouvertes.fr/tel-01531870
Contributor : Abes Star <>
Submitted on : Friday, June 2, 2017 - 8:56:07 AM
Last modification on : Thursday, April 11, 2019 - 7:58:22 AM
Long-term archiving on : Wednesday, December 13, 2017 - 9:40:43 AM

File

58358_TANG_2017_archivage.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-01531870, version 1

Citation

Jian Tang. From Silicon to Germanium Nanowires : growth processes and solar cell structures. Materials Science [cond-mat.mtrl-sci]. Université Paris-Saclay, 2017. English. ⟨NNT : 2017SACLX014⟩. ⟨tel-01531870⟩

Share

Metrics

Record views

718

Files downloads

861