monoPoly™ cells: Large-area crystalline silicon solar cells with fire-through screen printed contact to doped polysilicon surfaces

Duttagupta, Shubham; Nandakumar, Naomi; Padhamnath, Pradeep; Buatis, Jamaal Kitz; Stangl, Rolf; Aberle, Armin G.

doi:10.1016/j.solmat.2018.05.059

Cited by 81 publications

(43 citation statements)

References 18 publications

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“…Poly‐Si has been applied at the front side of FBC solar cells with transparent conductive oxide (TCO) or with SiN x as anti‐reflection coating for tandem device applications or at the rear side of industrial n‐type wafer‐based FBC cells However, placing thick poly‐Si layers at the front side of a solar cell induces consistent parasitic absorption estimated in the range of 1.5 mA/cm 2 each 30 nm of poly‐Si . Furthermore, poly‐Si accounts for free carrier absorption (FCA) in the near infrared (NIR) wavelength range .…”

Section: Introductionmentioning

confidence: 99%

Implantation‐based passivating contacts for crystalline silicon front/rear contacted solar cells

Limodio

Yang

Groot

et al. 2020

Progress in Photovoltaics

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In this work, we develop SiOx/poly‐Si carrier‐selective contacts grown by low‐pressure chemical vapor deposition and boron or phosphorus doped by ion implantation. We investigate their passivation properties on symmetric structures while varying the thickness of poly‐Si in a wide range (20‐250 nm). Dose and energy of implantation as well as temperature and time of annealing were optimized, achieving implied open‐circuit voltage well above 700 mV for electron‐selective contacts regardless the poly‐Si layer thickness. In case of hole‐selective contacts, the passivation quality decreases by thinning the poly‐Si layer. For both poly‐Si doping types, forming gas annealing helps to augment the passivation quality. The optimized doped poly‐Si layers are then implemented in c‐Si solar cells featuring SiO2/poly‐Si contacts with different polarities on both front and rear sides in a lean manufacturing process free from transparent conductive oxide (TCO). At cell level, open‐circuit voltage degrades when thinner p‐type poly‐Si layer is employed, while a consistent gain in short circuit current is measured when front poly‐Si thickness is thinned down from 250 to 35 nm (up to +4 mA/cm2). We circumvent this limitation by decoupling front and rear layer thickness obtaining, on one hand, reasonably high current (JSC‐EQE = 38.2 mA/cm2) and, on the other hand, relatively high VOC of approximately 690 mV. The best TCO‐free device using Ti‐seeded Cu‐plated front contact exhibits a fill factor of 75.2% and conversion efficiency of 19.6%.

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Section: Introductionmentioning

confidence: 99%

Implantation‐based passivating contacts for crystalline silicon front/rear contacted solar cells

Limodio

Yang

Groot

et al. 2020

Progress in Photovoltaics

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“…Many groups are working on different cell concepts. Clearly, the “most prominent” cell structure with passivating contacts is an n‐type cell with boron front emitter (including “unpassivated” front contacts) and n+ poly‐Si on the rear, denoted as “TOPCon”, “monoPoly”, “PaCo”, PERPoly, and so forth. Recently, an ISO 17025/IEC 6094 calibrated record efficiency of 24.6% has been announced for this structure on a large area cell.…”

mentioning

confidence: 99%

For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?

Peibst

Kruse

Schäfer

et al. 2019

Progress in Photovoltaics

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We present a systematic study on the benefit of the implementation of poly-Si on oxide (POLO) or related junctions into p-type industrial Si solar cells as compared with the benchmark of Passivated Emitter and Rear Cell (PERC). We assess three aspects: (a) the simulated efficiency potential of representative structures with POLO junctions for none (=PERC+), one, and for two polarities; (b) possible lean process flows for their fabrication; and (c) experimental results on major building blocks. Synergistic efficiency gain analysis reveals that the exclusive suppression of the contact recombination for one polarity by POLO only yields moderate efficiency improvements between 0.23% abs and 0.41% abs as compared with PERC+ because of the remaining recombination paths. This problem is solved in a structure that includes POLO junctions for both polarities (POLO 2 ), for whose realization we propose a lean process flow, and for which we experimentally demonstrate the most important building blocks. However, two experimental challenges-alignment tolerances and screen-print metallization of p+ poly-Si-are unsolved so far and reduced the efficiency of the "real" POLO 2 cell as compared with an idealized scenario. As an intermediate step, we therefore work on a POLO IBC cell with POLO junctions for one polarity. It avoids the abovementioned challenges of the POLO 2 structure, can be realized within a lean process flow, and has an efficiency benefit of 1.59% abs as compared with PERC-because not only contact recombination is suppressed but also the entire phosphorus emitter is replaced by an n+ POLO junction.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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“…[ 1–5 ] Currently many research groups work on passivated contacts based on polycrystalline Si on oxide (POLO) or related junction schemes, applying different approaches for their implementation into industrial solar cells. [ 6–9 ] One approach is to apply nonpatterned POLO contacts for both polarities on the cell front‐ and rear side. [ 10–17 ] As poly‐Si layer on the top of this cell concept should be less than 20 nm to avoid parasitic absorption and therefore has high sheet resistances (above 1000 Ω sq −1 ), [ 10 ] a highly conductive and transparent layer (transparent conductive oxides [TCO]) on top of the poly‐Si needs to ensure the required lateral conductivity for the transport of charge carriers toward the metallization grid on the front side.…”

Section: Introductionmentioning

confidence: 99%

Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells

et al. 2020

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Herein, the various measures to improve the efficiency of large‐area screen‐printed double‐side contacted polycrystalline Si on oxide (POLO)‐cells are experimentally demonstrated. The short‐circuit current density Jsc increases by 0.6 mA cm−2 upon reducing the thickness of poly‐Si from 25 to 10 nm due to the reduction of the parasitic absorption in the poly‐Si layer at the textured front side of the cell. Additionally, it is shown for the first time that the minority carriers generated by light absorbed in the poly‐Si layer can at least partially be transferred into the crystalline Si base. Remarkably high implied open‐circuit voltage Voc,impl values are achieved with n‐type cell precursors by introducing an hydrogenation step by AlxOy after reducing the poly‐Si thickness, and by an additional annealing step after sputtering of transparent conductive oxides (TCOs). All cell precursors show Voc,impl values of up to 740 mV independent of the poly‐Si thickness. A reduction in the open‐circuit voltage Voc is observed during back‐end processing to 728 mV as measured on the final cells. A certified cell energy conversion efficiency of 22.3% is reported.

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monoPoly™ cells: Large-area crystalline silicon solar cells with fire-through screen printed contact to doped polysilicon surfaces

Cited by 81 publications

References 18 publications

Implantation‐based passivating contacts for crystalline silicon front/rear contacted solar cells

Implantation‐based passivating contacts for crystalline silicon front/rear contacted solar cells

For none, one, or two polarities—How do POLO junctions fit best into industrial Si solar cells?

Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells

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