Interplay of annealing temperature and doping in hole selective rear contacts based on silicon-rich silicon-carbide thin films

Nogay, Gizem; Stückelberger, Josua; Wyss, Philippe; Rucavado, Esteban; Allebé, Christophe; Koida, Takashi; Morales‐Masis, Monica; Despeisse, Matthieu; Haug, Franz‐Josef; Ballif, Christophe

doi:10.1016/j.solmat.2017.06.039

Cited by 86 publications

(61 citation statements)

References 39 publications

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“…Reasonable J 0,met and contact resistivity (ρ c ) values can be achieved for heavily-doped, thick poly-Si films, but here the IR response is reduced noticeably due to free carrier absorption (FCA). In this paper, we focus on low-damage sputter deposition of ITO on thin PECVD poly-Si contacts [7][8][9][10][11] with the purpose to realize an optical spacer preventing surface plasmon absorption within the subsequent metal [12]. Successively sputtering of a TCO/metal stack is an economically attractive option for the rear metallization of a monofacial cell with (i) passivation quality, (ii) electrical contact properties and (iii) infrared response being important design parameters.…”

Section: Introductionmentioning

confidence: 99%

Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

Tutsch

Feldmann

Bivour

et al. 2018

AIP Conference Proceedings

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Abstract. This work addresses the development of a transparent conductive oxide (TCO)/metal stack for n-type Si solar cells featuring a tunnel oxide passivating rear contact (TOPCon). While poly-Si based passivating contacts contacted by local fire-through metallization currently show an increased recombination at the metal contacts and a poor infrared (IR) response, we aim to realize a full-area metallization which maintains the high level of surface passivation and avoids IR losses. Some research groups have reported that sputtering TCOs on poly-Si based passivating contacts degrades the surface passivation and unlike the SHJ cells this degradation cannot be cured completely at Tcure ~ 200°C. However, the higher thermal stability of TOPCon allows for higher Tcure of up to 400°C, which can effectively restore the surface passivation. On the other hand, the contact resistivity (ρc) of the TOPCon/ITO/metal contact increased by several orders of magnitude in our test structures during annealing at such high temperatures. Possible reasons like the formation of an interfacial oxide are currently under investigation. Increasing the poly-Si thickness and/or doping mitigated the effect of sputter damage, but this will come at the cost of more parasitic absorption. However, by adapting the sputter and the subsequent annealing process, we were able to realize low damage deposition of ITO (loss in implied Voc ~ 7 mV) on thin, lowly doped poly-Si layers on textured wafers, yielding reasonable contact properties (ρc ~ 40 mΩcm² of the whole rear contact stack).

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Section: Introductionmentioning

confidence: 99%

Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

Tutsch

Feldmann

Bivour

et al. 2018

AIP Conference Proceedings

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“…Finally, the stability of the surface passivation properties over time was shown to depend on the blister density. As shown before, the addition of a hydrogenation step is beneficial to the surface passivation properties of the poly‐Si/SiO x structure . In this study, the deposition of hydrogenated silicon nitride layer (SiN:H) on top of the poly‐Si layer followed by a firing step helped to further improved the surface passivation properties leading to promising surface passivation properties on KOH‐polished large area wafers.…”

Section: Introductionmentioning

confidence: 55%

“…A promising way to develop the poly‐Si/SiO x structure relies on the deposition of hydrogen‐rich amorphous silicon (a‐Si:H) by plasma enhanced chemical vapor deposition (PECVD), followed by an annealing step required to crystallize the a‐Si:H layer into poly‐Si . The PECVD approach enables to deposit the poly‐Si layer on a single side of the wafer, contrarily to Low Pressure CVD technique that involves a deposition on both sides of the wafer .…”

Section: Introductionmentioning

confidence: 99%

“…However, if not optimized, PECVD of a‐Si:H layer on top of SiO x involves a blistering of the layer due to its high hydrogen (H) content which causes a severe degradation of the poly‐Si layer after annealing . Alloying the a‐Si:H with carbon has been shown to solve the blistering issue . Blister‐free layers can be deposited without addition of carbon, as reported in ref.…”

Section: Introductionmentioning

confidence: 99%

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Conductivity and Surface Passivation Properties of Boron‐Doped Poly‐Silicon Passivated Contacts for c‐Si Solar Cells

Morisset

Cabal

Grange

et al. 2018

Physica Status Solidi (a)

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Passivating the contacts of crystalline silicon (c‐Si) solar cells with a poly‐crystalline silicon (poly Si) layer on top of a thin silicon oxide (SiOx) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the c‐Si substrate. This study focuses on the development of boron‐doped poly‐Si/SiOx structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photo‐voltage potential. The poly‐Si layer is obtained by depositing a hydrogen‐rich amorphous silicon layer by plasma enhanced chemical vapor deposition (PECVD) exposed then to an annealing step. Using the PECVD route enables to single side deposit the poly Si layer, however, a blistering of the layer appears due to its high hydrogen content, which leads to the degradation of the poly‐Si layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blister‐free poly‐Si layer. The stability of the surface passivation properties over time is shown to depend on the blister density. The surface passivation properties are further improved thanks to a post process hydrogenation step. As a result, a mean implied photo‐voltage value of 714 mV is obtained.

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“…The experiment was reproduced with an annealing step performed at 800°C. The passivation properties were stable and slightly improved after annealing at 800°C: an average iV oc value of 714 mV was obtained after firing with a maximum of 721 mV which is among the best values reported for PECV-deposited poly-Si(B) layers [7,8].…”

Section: Improvement Of the Passivation By Addition Of A Hydrogenatinmentioning

confidence: 67%

Improvement of the conductivity and surface passivation properties of boron-doped poly-silicon on oxide

Morisset¹,

Cabal²,

Grange³

et al. 2018

AIP Conference Proceedings

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Abstract. Passivating contacts of crystalline silicon (c-Si) solar cells with a poly-silicon layer (poly-Si) on a thin silicon oxide (SiOx) film offer an interesting approach to decrease the recombination current at the metal/c-Si interface and to increase the cell efficiency. This study focuses on the development of boron-doped poly-Si layers deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) on top of a thin silicon oxide film. First, the deposition and annealing conditions were optimised in order to: (1) reduce the blistering of the poly-Si on the thin SiOx film and (2) improve the poly-Si conductivity. The passivation properties of the resulting structures have been shown to depend on the blister density and have been improved through a hydrogenation step leading to a maximum implied open-circuit voltage value of 721 mV.

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Interplay of annealing temperature and doping in hole selective rear contacts based on silicon-rich silicon-carbide thin films

Cited by 86 publications

References 39 publications

Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

Conductivity and Surface Passivation Properties of Boron‐Doped Poly‐Silicon Passivated Contacts for c‐Si Solar Cells

Improvement of the conductivity and surface passivation properties of boron-doped poly-silicon on oxide

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