Challenges for lowly-doped phosphorus emitters in silicon solar cells with screen-printed silver contacts

Werner, Sabrina; Lohmüller, Elmar; Maier, Stefan A.; Mourad, Samer; Aßmus, W.

doi:10.1016/j.egypro.2017.09.274

Cited by 27 publications

(14 citation statements)

References 13 publications

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“…Our result also represents a considerable advance compared to conventional screen printed Ag metallisation on e.g. phosphorus‐doped emitters with J 0,met > 1000 fA cm −2 . The application is interesting for more industrial type high‐efficiency p‐type solar cells with boron‐doped polysilicon layer on the rear side and a screen‐printed metal grid on top with around 5% coverage, for which a total rear side recombination J 0,rear total contribution of ≈20 fA cm −2 is expected (assuming 840 °C firing).…”

mentioning

confidence: 72%

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: 72%

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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“…The ECV measurements are performed on initially alkaline textured surfaces and are corrected to match the local R sh measured by 4 pp in the area of the posterior ECV measurement point (the correction procedure is described in detail in Ref. ; the near‐surface correction is not performed in the present work as the surface depletion is not an artefact for boron doping profiles). As the textured surface is partly melted by the laser process, the resulting surface factor is smaller than for non‐lasered textured surfaces.…”

Section: Overview Of the Settings Used For Laser Doping From The Glasmentioning

confidence: 99%

Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

Lohmüller

2018

Physica Rapid Research Ltrs

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The concept of attaching a second deposition step at the end of boron tribromide (BBr3) diffusion is introduced, where second deposition describes an active nitrogen flow through the BBr3 bubbler. This approach provides a higher boron dose in the borosilicate glass (BSG) which facilitates the formation of laser‐doped selective emitters. It is found that the second deposition hardly impacts the as‐diffused charge carrier concentration profile in comparison to BBr3 diffusion without second deposition. The emitter sheet resistance Rsh ≈ 110 Ω sq−1 and emitter dark saturation current density j0e ≈ 25 fA cm−2 (alkaline textured, Al2O3/SiNX passivation) are similar for both processes. The BBr3 diffusion process forms a BSG/silicon dioxide (SiO2) stack layer on the silicon. The BBr3 diffusion with second deposition step results in an 8 nm thicker BSG/SiO2 stack layer (total thickness: 42 nm) with factor two higher boron dose compared to the BBr3 diffusion without second deposition. After laser doping, the charge carrier concentration is higher for the BBr3 process with second deposition resulting in stronger local doping with about 10 Ω sq−1 lower Rsh. For laser‐doped and Al2O3/SiNX‐passivated areas, a promising process combination results in j0e = (250 ± 30) fA cm−2 at Rsh = (65 ± 1) Ω sq−1.

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“…For high temperature diffused junction solar cells, the conductive layer is the heavily doped emitter, which shows a sheet resistance typically ranging from 40 Ω/□ to 100 Ω/□ 1 . Optimization of the diffused emitter has dealt with the trade-off between contact resistivity with metal grids and Auger recombination (increases quadratically with doping density) 2 . This compromise leads to fill factor (FF) losses for lower doping densities and opencircuit voltage (Voc) losses for higher doping densities.…”

Section: Introductionmentioning

confidence: 99%

“…ConclusionsIn the present work, we demonstrate a SHJ solar cell design substituting the TCO layer by lateral conduction of c-Si absorber. Using only the c-Si bulk for lateral conduction, excellent lateral carrier collection was verified by achieving a fill factor of 80.7% and a low series resistance of 0.32 Ω•cm2 . Metal diffusion into a-Si:H layer was observed in the direct metal/a-Si:H contacts.…”

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Transparent-conductive-oxide-free front contacts for high-efficiency silicon heterojunction solar cells

Pomaska

Lambertz

et al. 2021

Joule

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In order to compensate the insufficient conductance of heterojunction thin films, transparent conductive oxides (TCO) have been used for decades in both-sides contacted crystalline silicon heterojunction (SHJ) solar cells to provide lateral conduction for efficient carrier collection. In this work, we substitute the TCO layers by utilizing the lateral conduction of c-Si absorber, thereby enabling a TCO-free design. A series resistance of 0.32 Ωcm 2 and a fill factor of 80.7% were measured for a TCO-free back-junction SHJ solar cell with a conventional finger pitch of 1.8 mm, thereby proving that relying on lateral conduction in the c-Si bulk is compatible with low series resistances. Achieving high efficiencies in SHJ solar cells with TCO-free front contacts requires suppressing deterioration of the passivation quality induced by direct metal-a-Si:H contacts and in-diffusion of metal into the a-Si:H layer. We show that an ozone treatment at the a-Si:H/metal interface suppresses the metal diffusion and improves the passivation without increasing the

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Challenges for lowly-doped phosphorus emitters in silicon solar cells with screen-printed silver contacts

Cited by 27 publications

References 13 publications

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

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

Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

Transparent-conductive-oxide-free front contacts for high-efficiency silicon heterojunction solar cells

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Challenges for lowly-doped phosphorus emitters in silicon solar cells with screen-printed silver contacts

Cited by 27 publications

References 13 publications

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

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

Advanced BBr3 Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

Transparent-conductive-oxide-free front contacts for high-efficiency silicon heterojunction solar cells

Contact Info

Product

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Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping