Changes in hydrogen concentration and defect state density at the poly-Si/SiOx/c-Si interface due to firing

Hollemann, Christina; Folchert, Nils; Harvey, Steven P.; Stradins, Paul; Young, David L.; Souza, Caroline Lima Salles de; Rienäcker, Michael; Haase, Felix; Brendel, Rolf; Peibst, Robby

doi:10.1016/j.solmat.2021.111297

Cited by 22 publications

(20 citation statements)

References 31 publications

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“…The negative impact of excess hydrogen on surface passivation observed in this work agrees with the literature. , Hollemann et al . performed firing experiments on n-type poly-Si/SiO x passivated lifetime samples with AlO x and SiN x stacks by varying the AlO x thickness and the peak firing temperature and compared the interface defect density ( D it ) calculated by the MarcoPOLO model and the hydrogen concentration measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS).…”

Section: Resultssupporting

confidence: 89%

“…The negative impact of excess hydrogen on surface passivation observed in this work agrees with the literature. 44,45 Hollemann et al 44 performed firing experiments on n-type poly-Si/SiO x passivated lifetime samples with AlO x and SiN x stacks by varying the AlO x thickness and the peak firing temperature and compared the interface defect density (D it ) calculated by the MarcoPOLO model and the hydrogen concentration measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was observed that a hightemperature firing at 863 °C can lead to excessive hydrogenation, in which the hydrogen concentration was several times higher than the corresponding D it , 44 implying the presence of hydrogen-related defects.…”

Section: Impact Of Additional Hydrogenation After Firingmentioning

confidence: 99%

“…44,45 Hollemann et al 44 performed firing experiments on n-type poly-Si/SiO x passivated lifetime samples with AlO x and SiN x stacks by varying the AlO x thickness and the peak firing temperature and compared the interface defect density (D it ) calculated by the MarcoPOLO model and the hydrogen concentration measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was observed that a hightemperature firing at 863 °C can lead to excessive hydrogenation, in which the hydrogen concentration was several times higher than the corresponding D it , 44 implying the presence of hydrogen-related defects. In addition, Gotoh et al 45 studied the influence of the deposition temperature on the passivation performance and the hydrogen concentration in a-Si:H/c-Si heterojunctions with hydrogen depth profiling by nuclear reaction analysis.…”

Section: Impact Of Additional Hydrogenation After Firingmentioning

confidence: 99%

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Optimum Hydrogen Injection in Phosphorus-Doped Polysilicon Passivating Contacts

Kang

Sio

Stückelberger

et al. 2021

ACS Appl. Mater. Interfaces

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It has previously been shown that ex situ phosphorus-doped polycrystalline silicon on silicon oxide (poly-Si/SiO x ) passivating contacts can suffer a pronounced surface passivation degradation when subjected to a firing treatment at 800 °C or above. The degradation behavior depends strongly on the processing conditions, such as the dielectric coating layers and the firing temperature. The current work further studies the firing stability of poly-Si contacts and proposes a mechanism for the observed behavior based on the role of hydrogen. Secondary ion mass spectrometry is applied to measure the hydrogen concentration in the poly-Si/SiO x structures after firing at different temperatures and after removing hydrogen by an anneal in nitrogen. While it is known that a certain amount of hydrogen around the interfacial SiO x can be beneficial for passivation, surprisingly, we found that the excess amount of hydrogen can deteriorate the poly-Si passivation and increase the recombination current density parameter J 0. The presence of excess hydrogen is evident in selected poly-Si samples fired with silicon nitride (SiN x ), where the injection of additional hydrogen to the SiO x interlayer leads to further degradation in the J 0, while removing hydrogen fully recovers the surface passivation. In addition, the proposed model explains the dependence of firing stability on the crystallite properties and the doping profile, which determine the effective diffusivity of hydrogen upon firing and hence the amount of hydrogen around the interfacial SiO x after firing.

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Section: Resultssupporting

confidence: 89%

Section: Impact Of Additional Hydrogenation After Firingmentioning

confidence: 99%

Section: Impact Of Additional Hydrogenation After Firingmentioning

confidence: 99%

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Optimum Hydrogen Injection in Phosphorus-Doped Polysilicon Passivating Contacts

Kang

Sio

Stückelberger

et al. 2021

ACS Appl. Mater. Interfaces

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“…[ 18 ] Using Equation (), J gen = 38 mA cm −2 , and iV OC = 572 mV, the surface and bulk recombination

J_{0} = false(J_{0, bulk} + 2 * J_{0 s} false)

from the in situ doped sample before hydrogenation calculates to 8146 fA cm − 2 . Assuming that the hydrogen mostly passivates the defects at the interface rather than in the bulk, [ 19 ] the low values of J 0s after hydrogenation in Figure indicate J 0,bulk to be orders of magnitudes lower than the

false(J_{0, bulk} + 2 * J_{0 s} false)

calculated using the one‐diode model. Therefore, we conclude that the surface recombination is approximated as high as J 0s ≈ 4073 fA cm − 2 .…”

Section: Resultsmentioning

confidence: 99%

Sputtered Phosphorus‐Doped poly‐Si on Oxide Contacts for Screen‐Printed Si Solar Cells

et al. 2022

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The impact of the phosphorus doping density in direct current‐sputtered polysilicon layers on surface passivation and contact resistance by fabricating polysilicon on oxide (POLO) contacts is studied, when applying doping densities ranging from 3 × 1019 to 4 × 1020 cm−3. Hydrogenation is performed either via a hydrogen‐releasing AlO x layer and postdeposition anneals in forming gas using a tube furnace at 400 °C, or by rapid firing of an AlO x /SiN y stack in a conveyor belt furnace at 810 °C. The study shows that the forming gas anneal of the weakly in situ phosphorus‐doped poly‐Si layers with AlO x enables a passivation quality with an implied open‐circuit voltage of up to 734 mV and a recombination current density down to 1.8 fA cm− 2. For fast firing, a high phosphorus concentration of 4 × 1020 cm−3 is required for comparably high passivation quality with a recombination current density down to 1.3 fA cm− 2. A p‐type POLO back‐junction solar cell featuring such ex situ doped sputtered POLO contacts with a cell efficiency of 22.4% and an open‐circuit voltage of 714 mV is fabricated. To our knowledge, this is the highest open‐circuit voltage published so far with sputtered POLO contacts.

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“…However, the microstructural regulation of Si lm has a decisive impact on the interface passivation of passivated contact in TOPCon solar cells. [12][13][14] It is benet to improve the eld effect passivation and reduce the interface defects density. Therefore, to obtain high performance in TOPCon silicon solar cells, some reports on the microstructure of pre-deposited Si layer were implemented.…”

Section: Introductionmentioning

confidence: 99%