Light-induced anodisation of silicon for solar cell passivation

Cui, Jie; Wang, X.; Opila, R. L.; Lennon, Alison

doi:10.1063/1.4829701

Cited by 17 publications

(14 citation statements)

References 45 publications

(41 reference statements)

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“…In this technique, one side of the silicon wafer is in contact with the electrolyte, and the front illuminated side has a transparent positive contact resting on its surface. Although the technique developed by Cui et al is significantly different from the "clip"-based technique we have previously used, the surface passivation attained by LIA is comparable with our previous results when the same annealing treatment is performed, i.e., O 2 and FG at 400°C [15].…”

supporting

confidence: 87%

“…At this time, it is unclear whether the Si 3 N 4 film prevents the ingression of moisture or whether the deposition has changed the properties of the underlying SiO 2 film and, therefore, reduced the oxides susceptibility to moisture degradation. However, given that LPCVD Si 3 N 4 has a higher film density (∼3 g/cm 3 ) than PECVD SiN x (∼2 g/cm 3 ) [29], [30] indicates LPCVD Si 3 N 4 could also act as an effective moisture barrier and, therefore, prevent moisture degradation at the Si/SiO 2 interface, as demonstrated by PECVD SiN x [15], [31].…”

Section: Surface Passivation Ageingmentioning

confidence: 99%

“…Another drawback of the anodic oxidation technique is the requirement to electrically contact the silicon wafer, meaning some portion of the wafer cannot be immersed in the electrolyte. Recently, however, Cui et al have addressed this limitation by performing full-area single-sided light-induced anodic (LIA) oxidations [14], [15]. In this technique, one side of the silicon wafer is in contact with the electrolyte, and the front illuminated side has a transparent positive contact resting on its surface.…”

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confidence: 99%

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High-Level Silicon Surface Passivation by Anodically Grown Silicon Dioxide and Silicon Nitride Stacks

Grant

Kho

Weber

2015

IEEE J. Photovoltaics

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We investigate the surface passivation attained by a stack consisting of anodically grown silicon dioxide and silicon nitride. A very low surface saturation current density J os of 3 fA/cm 2 is attained after the silicon wafers are submersed in nitric acid under a constant bias for >30 min, followed by a silicon nitride deposition and subsequent annealing in forming gas (FG) at 400°C. We examine J os as a function of the anodic SiO 2 thickness (d ox ) and show that for d ox between 7 and 36 nm, J os decreases monotonically from 32 to 3 fA/cm 2 , respectively. From capacitance-voltage (CV) and conductance measurements, we show that this reduction in J os with an increase in oxide thickness primarily results from a reduction in both the interface defect density (D it ) and the hole capture cross section (σ p ). For the lowest J os of 3 fA/cm 2 , a low D it of ∼ 2.0 × 10 10 cm −2 ·eV −1 and a low σ p of ∼ 1 × 10 −16 cm −2 are determined. When the anodic SiO 2 films are capped by a silicon nitride film, negligible surface passivation degradation occurs, in comparison with uncapped anodic SiO 2 films. Finally, we demonstrate that thermally induced bulk silicon defects can be eliminated by replacing high temperature (1000°C) oxidations with a room-temperature anodic oxidation technique.

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supporting

confidence: 87%

Section: Surface Passivation Ageingmentioning

confidence: 99%

mentioning

confidence: 99%

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High-Level Silicon Surface Passivation by Anodically Grown Silicon Dioxide and Silicon Nitride Stacks

Grant

Kho

Weber

2015

IEEE J. Photovoltaics

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“…The recently developed light-induced anodisation (LIA) method [5] utilises light-induced current of the solar cell resulting in an anodic p-type surface, and when the cell is single-side immersed in a suitable electrolyte, a uniform silicon dioxide layer can be formed. In the present study, the properties of the anodic silicon dioxide formed by LIA method were studied.…”

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confidence: 99%

Characterization of Silicon Oxides Formed by Light-Induced Anodisation for Silicon Solar Cell Surface Passivation

et al. 2014

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In this paper we report the properties of the anodic silicon dioxide film formed using light-induced anodisation (LIA) method and its potential to be used as surface passivation layer of p-type silicon surfaces of silicon solar cells. The high uniformity of the formed oxide is possibly due to the uniform drift of the positive charge carriers in the silicon to the surface being anodised. The oxide grows at higher rate than that in nitric acid, an oxide layer with thickness of 18 nm can be formed by anodising for 10 min with 15 V bias in 0.5 M sulphuric acid. After annealing in oxygen and then forming gas at 400 ºC for 30 min, an average effective carrier lifetime of 120 µs was measured by quasi-steady state photoluminance on 180 µm p-type 3-5 Ohm cm Cz silicon wafers, with a value of 110 µs being measured for the same wafers passivated by a thermally-grown oxide of the same thickness. The properties of the anodic silicon dioxide layers formed by LIA have been characterized by ellipsometry, x-ray photoelectron spectroscopy, quasi-steady state photoluminance and Fourier transform infrared spectroscopy.

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“…Experimental realization of LIA required the development of a patterned soft electrode to enable the application of both a bias voltage and illumination from the n-type surface of the wafer. In LIA of silicon [8], light can be provided through the electrolyte, a process that is commonly used for light-induced plating of silicon solar cells [21]. However, this arrangement is not applicable to anodizing metal layers, such as aluminum, which are opaque before anodization.…”

mentioning

confidence: 99%

Ultralow Interface State Density Achieved by Light-Induced Anodization of Aluminum on Silicon Solar Cell Surfaces

Cui

Ouyang

Hameiri

et al. 2015

IEEE J. Photovoltaics

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A light-induced anodization (LIA) method, which uses the light-induced current of a silicon solar cell to anodize aluminum and form an anodic aluminum oxide (AAO) layer that can reduce recombination at a p-type surface of the cell, is reported. This method can result in anodic oxides with uniform properties over the surfaces of industrially sized silicon wafers since the current flows through the wafer rather than in the surface aluminum layer, as it does when the aluminum is directly electrically contacted. Uniform AAO layers can be formed within 4 min on p-type silicon surfaces by anodizing 300-nm-thick aluminum layers, and when formed over a thin interfacial silicon dioxide layer, the interface state density at the p-type silicon wafer interface can be reduced to values as low as 1 × 10 10 cm −2 ·eV −1 and a fixed charge density of 2 × 10 11 cm −2 . Photoconductance carrier lifetime measurements indicate that these AAO dielectric stack layers are capable of passivating silicon surfaces to a level similar to that provided by silicon nitride layers, which are deposited using plasma-enhanced chemical vapor deposition, although at potentially a much-reduced cost. The high-quality surface passivation, rapid room temperature processing, and large-area uniformity of LIA make it a promising method for producing passivation materials that can further improve efficiency and potentially reduce the cost of photovoltaic solar cells and other p-n junction devices.Index Terms-Anodic aluminum oxide (AAO), light-induced anodization (LIA), photovoltaic solar cell, surface passivation.

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Light-induced anodisation of silicon for solar cell passivation

Cited by 17 publications

References 45 publications

High-Level Silicon Surface Passivation by Anodically Grown Silicon Dioxide and Silicon Nitride Stacks

High-Level Silicon Surface Passivation by Anodically Grown Silicon Dioxide and Silicon Nitride Stacks

Characterization of Silicon Oxides Formed by Light-Induced Anodisation for Silicon Solar Cell Surface Passivation

Ultralow Interface State Density Achieved by Light-Induced Anodization of Aluminum on Silicon Solar Cell Surfaces

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