Study of screen printed metallization for polysilicon based passivating contacts

Janssen, G.J.M.; Geerligs, L.J.; Löffler, J.; Wu, Yu Cheng; Stodolny, M.K.; Luchies, J.M.; Lenes, Martijn; Ciftpinar, Emine Hande; Schmitz, Jurriaan

doi:10.1016/j.egypro.2017.09.242

Cited by 75 publications

(64 citation statements)

References 12 publications

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“…Typically, metallisation of passivating contacts is realized by physical vapor deposition of a transparent conductive oxide or metals like aluminum or silver, but also screen printing was used for contacting n + polysilicon layers by Ag pastes or for contacting p + polysilicon layers by AgAl pastes …”

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confidence: 99%

Metallisation of Boron‐Doped Polysilicon Layers by Screen Printed Silver Pastes

Mack

Schube

Fellmeth

et al. 2017

Physica Rapid Research Ltrs

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In this work, we report on hole selective passivating contacts, which consist of a SiOx tunnel layer and an in situ boron‐doped 300 nm thick p+ polysilicon layer deposited by LPCVD. Using a SiNx:H capping layer, we show an extremely low dark saturation current density J0 of 1 fA cm−2 after contact firing. At the same time, we demonstrate that commercially available and screen‐printed fire through Ag pastes are capable of contacting the p+ polysilicon layer, with minimum contact resistance ρc = 2 mΩ cm2. We do find increased interface recombination below the metal contacts of around 250 fA cm−2, which represents a considerable advance compared to conventional screen printed metallisation on diffused junctions.

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confidence: 99%

Metallisation of Boron‐Doped Polysilicon Layers by Screen Printed Silver Pastes

Mack

Schube

Fellmeth

et al. 2017

Physica Rapid Research Ltrs

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“…to < 22% for bifacial cells on 6" Cz wafers in [4]). In essence, LPCVD poly-Si contacts contacted by fire-through metallization become locally depassivated, due to the penetration of metal through the polySi layer into the c-Si absorber (J 0,met » J 0,pass [5,6]). 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).…”

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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“…A very low J 0,metal of 20 fA/cm 2 at the rear metal fingers indicates a significant reduction in recombination at the metal contacts when compared with a standard screen-printed contact on diffused n + Si. 35 Together with a reduction in J 0,pass at the nonmetallized regions to 9 fA/cm 2 , this explains the high cell V oc values obtained. Solar cell precursors fired after passivation with no metallization (asymmetric samples with no metal contacts), gave an iV oc of 710 mV when measured by QSS-PC.…”

Section: Solar Cell Resultsmentioning

confidence: 68%

“…The saturation current density at the rear metal contacts ( J 0,metal ) and in the passivated regions ( J 0,pass ) after screen‐printing and firing, as determined using Griddler 2.5 (extracted by finding a common set of J 0 parameters that fit the Suns‐PL curves of the sample with varying metal fractions), are also presented in Table . A very low J 0,metal of 20 fA/cm 2 at the rear metal fingers indicates a significant reduction in recombination at the metal contacts when compared with a standard screen‐printed contact on diffused n + Si . Together with a reduction in J 0,pass at the nonmetallized regions to 9 fA/cm 2 , this explains the high cell V oc values obtained.…”

Section: Resultsmentioning

confidence: 79%

Approaching 23% with large‐area monoPoly cells using screen‐printed and fired rear passivating contacts fabricated by inline PECVD

Nandakumar

Rodriguez

Kluge

et al. 2018

Progress in Photovoltaics

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We present n‐type bifacial solar cells with a rear interfacial SiOx/n+:poly‐Si passivating contact (‘monoPoly’ cells) where the interfacial oxide and n+:poly‐Si layers are fabricated using an industrial inline plasma‐enhanced chemical vapor deposition (PECVD) tool. We demonstrate outstanding passivation quality with dark saturation current density (J0) values of approximately 3 fA/cm2 and implied open‐circuit voltage (iVoc) of 730 mV at 1‐sun conditions after firing in an industrial belt furnace. Using a simple solar cell process flow that can be easily adapted for mass production, a peak cell efficiency of 22.8% with a cell open circuit voltage (Voc) of 696 mV is achieved on large‐area, screen‐printed, Czochralski‐silicon (Cz‐Si) solar cells using commercial fire‐through metal pastes.

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Study of screen printed metallization for polysilicon based passivating contacts

Cited by 75 publications

References 12 publications

Metallisation of Boron‐Doped Polysilicon Layers by Screen Printed Silver Pastes

Metallisation of Boron‐Doped Polysilicon Layers by Screen Printed Silver Pastes

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

Approaching 23% with large‐area monoPoly cells using screen‐printed and fired rear passivating contacts fabricated by inline PECVD

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