Highly improved passivation of PECVD p-type TOPCon by suppressing plasma-oxidation ion-bombardment-induced damages

Ma, Dongying; Liu, Wei; Xiao, Mingjing; Yang, Zhenhai; Liu, Zunke; Liao, Mingdun; Han, Qingling; Cheng, Hao; Xing, Haiyang; Ding, Zeyu; Yan, Baojie; Wang, Yude; Zeng, Yuheng; Ye, Jichun

doi:10.1016/j.solener.2022.07.003

Cited by 15 publications

(4 citation statements)

References 30 publications

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“…Figure 13a compares the measured iV OC of the samples with and without SiO 2 for a poly Si layer with d poly Si,1 = 155 nm. For H p < 4.6 J/cm 2 , the majority of samples with SiO 2 show a good passivation quality with the highest iV OC = 721 mV, which is comparable with the highest reported values for p + -poly Si/SiO 2 passivation stacks [38,39]. The reason for the slight reduction in iV OC for 2 J/cm 2 < H p < 2.6 J/cm 2 is not clear and requires further scrutiny.…”

Section: Passivationsupporting

confidence: 55%

Laser Activation for Highly Boron-Doped Passivated Contacts

Sharbaf Kalaghichi,

Hoß,

Zapf-Gottwick

et al. 2023

Solar

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Passivated, selective contacts in silicon solar cells consist of a double layer of highly doped polycrystalline silicon (poly Si) and thin interfacial silicon dioxide (SiO2). This design concept allows for the highest efficiencies. Here, we report on a selective laser activation process, resulting in highly doped p++-type poly Si on top of the SiO2. In this double-layer structure, the p++-poly Si layer serves as a layer for transporting the generated holes from the bulk to a metal contact and, therefore, needs to be highly conductive for holes. High boron-doping of the poly Si layers is one approach to establish the desired high conductivity. In a laser activation step, a laser pulse melts the poly Si layer, and subsequent rapid cooling of the Si melt enables electrically active boron concentrations exceeding the solid solubility limit. In addition to the high conductivity, the high active boron concentration in the poly Si layer allows maskless patterning of p++-poly Si/SiO2 layers by providing an etch stop layer in the Si etchant solution, which results in a locally structured p++-poly Si/SiO2 after the etching process. The challenge in the laser activation technique is not to destroy the thin SiO2, which necessitates fine tuning of the laser process. In order to find the optimal processing window, we test laser pulse energy densities (Hp) in a broad range of 0.7 J/cm2 ≤ Hp ≤ 5 J/cm2 on poly Si layers with two different thicknesses dpoly Si,1 = 155 nm and dpoly Si,2 = 264 nm. Finally, the processing window 2.8 J/cm2≤ Hp ≤ 4 J/cm2 leads to the highest sheet conductance (Gsh) without destroying the SiO2 for both poly Si layer thicknesses. For both tested poly Si layers, the majority of the symmetric lifetime samples processed using these Hp achieve a good passivation quality with a high implied open circuit voltage (iVOC) and a low saturation current density (J0). The best sample achieves iVOC = 722 mV and J0 = 6.7 fA/cm2 per side. This low surface recombination current density, together with the accompanying measurements of the doping profiles, suggests that the SiO2 is not damaged during the laser process. We also observe that the passivation quality is independent of the tested poly Si layer thicknesses. The findings of this study show that laser-activated p++-poly Si/SiO2 are not only suitable for integration into advanced passivated contact solar cells, but also offer the possibility of maskless patterning of these stacks, substantially simplifying such solar cell production.

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Section: Passivationsupporting

confidence: 55%

Laser Activation for Highly Boron-Doped Passivated Contacts

Sharbaf Kalaghichi,

Hoß,

Zapf-Gottwick

et al. 2023

Solar

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“…[ 19–21 ] Conversely, boron‐doped (B‐doped) poly ‐Si contacts have a lower iV oc of ∼710 mV with a J 0 value of ∼10 fA cm −2 . [ 6,22 ] This phenomenon of inferior boron‐doped contacts was previously observed in the bipolar junction and field‐effect transistors in the 1990s. [ 23,24 ] Several studies have attributed it to the tendency of B to segregate at the interface between SiO x and c ‐Si, [ 25–30 ] increasing the density of interface defects.…”

Section: Introductionmentioning

confidence: 65%

Pulsed Laser Annealed Ga Hyperdoped Poly‐Si/SiO_x Passivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells

Chen

Napolitani

Tullio

et al. 2023

Energy & Environ Materials

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Polycrystalline Si (poly‐Si)‐based passivating contacts are promising candidates for high‐efficiency crystalline Si solar cells. We show that nanosecond‐scale pulsed laser melting (PLM) is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit. We demonstrate that conventionally doped, hole‐selective poly‐Si/SiOx contacts that provide poor surface passivation of c‐Si can be replaced with Ga‐ or B‐doped contacts based on non‐equilibrium doping. We overcome the solid solubility limit for both dopants in poly‐Si by rapid cooling and recrystallization over a timescale of ∼25 ns. We show an active Ga dopant concentration of ∼3 × 1020 cm−3 in poly‐Si which is six times higher than its solubility limit in c‐Si, and a B dopant concentration as high as ∼1021 cm−3. We measure an implied open‐circuit voltage of 735 mV for Ga‐doped poly‐Si/SiOx contacts on Czochralski Si with a low contact resistivity of 35.5 ± 2.4 mΩ cm2. Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p‐n junction that contributes to the low contact resistivity. Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high‐efficiency devices.

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“…In this work, industry-compatible fabrication methods, such as ambient-pressure thermal oxidation (APTO) and in-situ plasma-enhanced chemical vapor deposition (PECVD), are employed to prepare highly passivated p-TOPCon structures and double-sided TOPCon bottom cells on industrial textured wafers. The use of thermal oxidation avoids damages from ion-bombardment during the high-power plasma oxidation 11,12 , and in-situ PECVD realizes single-side deposition and doping with high versatility. Chemical and fieldeffect passivation are significantly promoted through mitigating ultrathin SiOx distortion by stronger oxidation, enhancing boron in-diffusion by employing a higher thermal budget, and suppressing high residual defect density by strengthened hydrogenation.…”

Section: Introductionmentioning

confidence: 99%

Highly passivated TOPCon bottom cells for perovskite/silicon tandem solar cells

Ye,

Ding,

Kan

et al. 2024

Preprint

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Tunnel oxide passivating contact (TOPCon) silicon solar cells are rising as a competitive photovoltaic technology, seamlessly blending high efficiency with cost-effectiveness and mass production capabilities. However, the numerous defects from the fragile silicon oxide/c-Si interface and the low field-effect passivation due to the inadequate boron in-diffusion in p-type TOPCon (p-TOPCon) reduce their open-circuit voltages (VOCs), impeding their widespread application in the promising perovskite/silicon tandem solar cells (TSCs) that hold a potential to break 30% module efficiency. To address this, we develop highly passivated p-TOPCon structure by optimizing the oxidation conditions, boron in-diffusion and aluminium oxide hydrogenation, thus pronouncedly improving the implied VOC (iVOC) of p-TOPCon to 715 mV and the VOC of double-sided TOPCon bottom cells to 710 mV. Consequently, integrating with perovskite top cells, our proof of concept 1 cm2 n-i-p perovskite/silicon TSCs exhibit VOCs exceeding 1.9 V and a highest reported efficiency of 28.20%, which paves a way for TOPCon cells in the commercialization of future tandems.

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Highly improved passivation of PECVD p-type TOPCon by suppressing plasma-oxidation ion-bombardment-induced damages

Cited by 15 publications

References 30 publications

Laser Activation for Highly Boron-Doped Passivated Contacts

Laser Activation for Highly Boron-Doped Passivated Contacts

Pulsed Laser Annealed Ga Hyperdoped Poly‐Si/SiO_x Passivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells

Highly passivated TOPCon bottom cells for perovskite/silicon tandem solar cells

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Highly improved passivation of PECVD p-type TOPCon by suppressing plasma-oxidation ion-bombardment-induced damages

Cited by 15 publications

References 30 publications

Laser Activation for Highly Boron-Doped Passivated Contacts

Laser Activation for Highly Boron-Doped Passivated Contacts

Pulsed Laser Annealed Ga Hyperdoped Poly‐Si/SiOx Passivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells

Highly passivated TOPCon bottom cells for perovskite/silicon tandem solar cells

Contact Info

Product

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Pulsed Laser Annealed Ga Hyperdoped Poly‐Si/SiO_x Passivating Contacts for High‐Efficiency Monocrystalline Si Solar Cells