Polysilicon passivated junctions: The next technology for silicon solar cells?

Yan, Donghang; Cuevas, Andrés; Michel, J.; Zhang, Chun; Wan, Yimao; Zhang, Xinyu; Bullock, James

doi:10.1016/j.joule.2021.02.013

Cited by 103 publications

(84 citation statements)

References 120 publications

(232 reference statements)

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“… 3 , 4 One of the most promising passivating contacts to rapidly bridge the gap between device efficiencies in R&D and those in production is based on a highly doped polycrystalline silicon (poly-Si) layer on top of a thin silicon oxide (SiO x ) buffer layer. 5 Due to its resilience at high temperatures, the poly-Si/SiO x contact promises compatibility with the mainstream metallization process currently used in the industry and thus a rapid increase of the c-Si solar cell efficiency beyond 24% in mass production. 5 − 7 …”

Section: Introductionmentioning

confidence: 99%

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In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

Morisset

Famprikis

Haug

et al. 2022

ACS Appl. Mater. Interfaces

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The integration of passivating contacts based on a highly doped polycrystalline silicon (poly-Si) layer on top of a thin silicon oxide (SiO x ) layer has been identified as the next step to further increase the conversion efficiency of current mainstream crystalline silicon (c-Si) solar cells. However, the interrelation between the final properties of poly-Si/SiO x contacts and their fabrication process has not yet been fully unraveled, which is mostly due to the challenge of characterizing thin-film stacks with features in the nanometric range. Here, we apply in situ X-ray reflectometry and diffraction to investigate the multiscale (1 Å–100 nm) structural evolution of poly-Si contacts during annealing up to 900 °C. This allows us to quantify the densification and thinning of the poly-Si layer during annealing as well as to monitor the disruption of the thin SiO x layer at high temperature >800 °C. Moreover, results obtained on a broader range of thermal profiles, including firing with dwell times of a few seconds, emphasize the impact of high thermal budgets on poly-Si contacts’ final properties and thus the importance of ensuring a good control of such high-temperature processes when fabricating c-Si solar cells integrating such passivating contacts. Overall, this study demonstrates the robustness of combining different X-ray elastic scattering techniques (here XRR and GIXRD), which present the unique advantage of being rapid, nondestructive, and applicable on a large sample area, to unravel the multiscale structural evolution of poly-Si contacts in situ during high-temperature processes.

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Section: Introductionmentioning

confidence: 99%

“… 5 Due to its resilience at high temperatures, the poly-Si/SiO x contact promises compatibility with the mainstream metallization process currently used in the industry and thus a rapid increase of the c-Si solar cell efficiency beyond 24% in mass production. 5 − 7 …”

Section: Introductionmentioning

confidence: 99%

In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

Morisset

Famprikis

Haug

et al. 2022

ACS Appl. Mater. Interfaces

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“…[ 3–5 ] Low pressure chemical vapor deposition (LPCVD) is currently the mainstream amorphous/polycrystalline silicon layer (a‐Si/poly‐Si) deposition technology used to fabricate industrial TOPCon cells. [ 6,7 ] Apart from high deposition rates, LPCVD allows in‐situ thermal oxidation of crystalline silicon (c‐Si) surface to form a tunnel oxide before deposition of poly‐Si layers in the same tube. However, since a‐Si/poly‐Si layer is inherently deposited on both sides of the wafer, a single‐sided etching (SSE) of this layer is required on the front side for typical TOPCon configuration in n‐type substrate, where the TOPCon layer is placed at the rear‐side of the cell.…”

Section: Introductionmentioning

confidence: 99%

“…[ 9 ] Physical vapor deposition (PVD) is reported to provide single‐sided poly‐Si deposition; [ 10 ] however, an industrial process is still under development. [ 7,11 ]…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Pressure Dry Etching of Polysilicon Layers for Highly Reverse Bias‐Stable TOPCon Solar Cells

et al. 2021

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Single‐sided etching (SSE) of a‐Si/poly‐Si is typically considered a challenge for realizing a cost‐efficient TOPCon production sequence, as there is a certain degree of unwanted wrap‐around for poly‐Si deposition technologies such as low pressure chemical vapor deposition, plasma‐enhanced chemical vapor deposition, and atmospheric pressure chemical vapor deposition. To date, alkaline or acidic wet‐chemical solutions in either inline or batch configurations are used for this purpose. Herein, an alternative SSE process is proposed using an inline dry etching tool, which applies molecular fluorine as the etching gas under atmospheric pressure conditions. The developed etching process performs complete etching of both as‐deposited amorphous silicon and annealed polycrystalline silicon layers, either intrinsic or doped, and with measured etch rates of >3 μm min−1 at 10% F2 concentration allows etching of a typical layer thickness of 200 nm in just a few seconds. The etching process is also configured to perform excellent edge isolation while maintaining a low wrap‐around etching (d rear < 500 μm) at the opposing‐side. The etching process is successfully transferred to the industrial TOPCon solar cell architecture, yielding high parallel resistances (S shunt,avg. > 1500 kΩ cm2), low reverse current density (J rev,avg < 0.8 mA cm−2) measured at a bias voltage of −12 V, and independently certified conversion efficiencies of up to 23.3%.

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“…For commercial application of tandem solar cells, silicon solar cells should enable the manufacturing of inexpensive, mass-produced cells that tolerate high temperatures [7]. The silicon solar-cell technology that has garnered the most attention is the carrier-selective contact structure, using a thin tunnel oxide and polysilicon [8,9]. This structure was first unveiled by Fraunhofer ISE as a tunnel oxide passivated contact (TOPCon) structure, and achieved 26.0% conversion efficiency over an area of 4 cm 2 by incorporating a phosphorusdoped polysilicon layer and a passivated, thin silicon oxide (SiO 2 ) film on the silicon surface to selectively transfer electrons [10].…”

Section: Introductionmentioning

confidence: 99%

Amorphous Silicon Thin Film Deposition for Poly-Si/SiO2 Contact Cells to Minimize Parasitic Absorption in the Near-Infrared Region

et al. 2021

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Tunnel oxide passivated contact (TOPCon) solar cells are key emerging devices in the commercial silicon-solar-cell sector. It is essential to have a suitable bottom cell in perovskite/silicon tandem solar cells for commercial use, given that good candidates boost efficiency through increased voltage. This is due to low recombination loss through the use of polysilicon and tunneling oxides. Here, a thin amorphous silicon layer is proposed to reduce parasitic absorption in the near-infrared region (NIR) in TOPCon solar cells, when used as the bottom cell of a tandem solar-cell system. Lifetime measurements and optical microscopy (OM) revealed that modifying both the timing and temperature of the annealing step to crystalize amorphous silicon to polysilicon can improve solar cell performance. For tandem cell applications, absorption in the NIR was compared using a semitransparent perovskite cell as a filter. Taken together, we confirmed the positive results of thin poly-Si, and expect that this will improve the application of perovskite/silicon tandem solar cells.

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Polysilicon passivated junctions: The next technology for silicon solar cells?

Cited by 103 publications

References 120 publications

In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

In Situ Reflectometry and Diffraction Investigation of the Multiscale Structure of p-Type Polysilicon Passivating Contacts for c-Si Solar Cells

Atmospheric Pressure Dry Etching of Polysilicon Layers for Highly Reverse Bias‐Stable TOPCon Solar Cells

Amorphous Silicon Thin Film Deposition for Poly-Si/SiO2 Contact Cells to Minimize Parasitic Absorption in the Near-Infrared Region

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