Passivation of Optically Black Silicon by Atomic Layer Deposited Al2O3

Otto, Martin; Kröll, Matthias; Käsebier, Thomas; Ziegler, Johannes; Sprafke, Alexander; Wehrspohn, Ralf B.

doi:10.1016/j.egypro.2013.07.357

Cited by 14 publications

(12 citation statements)

References 13 publications

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“…These surface and sub‐surface defects, together with an altered thickness of the passivating layer, explain the significant loss in minority‐carrier lifetime observed for dry‐plasma‐etched nanopatterned silicon wafers. A more conformal passivating layer such as aluminum oxide deposited by atomic layer deposition (ALD) would possibly result in better performance . However, for thin‐film technologies on foreign substrates , where the heterojunction emitter is on the nanopattern side and a transparent conducting oxide is needed, such a passivating layer is not an option.…”

Section: Resultsmentioning

confidence: 99%

Photonic nanostructures for advanced light trapping in silicon solar cells: the impact of etching on the material electronic quality

Trompoukis

Stesmans

Simoen

et al. 2015

Physica Rapid Research Ltrs

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Dry plasma etching, commonly used by the Photonics community as the etching technique for the fabrication of photonic nanostructures, could be a source of device performance limitations when used in the frame of silicon photovoltaics. So far, the lack of silicon solar cells with state‐of‐the‐art efficiencies utilizing nanophotonic concepts shows how challenging their integration is, owing to the trade‐off between optical and electrical properties. In this study we show that dry plasma etching results in the degradation of the silicon material quality due to (i) a high density of dangling bonds and (ii) the presence of sub‐surface defects, resulting in high surface recombination velocities and low minority carrier lifetimes. On the contrary, wet chemical anisotropic etching used as an alternative, leads to the formation of inverted nanopyramids that result in low surface recombination velocity and low density of dangling bonds. The proposed inverted nanopyramids could enable high efficiency photonic assisted solar cells by offering the potential to achieve higher short‐circuit current without degrading the open circuit voltage. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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Section: Resultsmentioning

confidence: 99%

Photonic nanostructures for advanced light trapping in silicon solar cells: the impact of etching on the material electronic quality

Trompoukis

Stesmans

Simoen

et al. 2015

Physica Rapid Research Ltrs

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“…Published by AIP Publishing. 122, 143101-1 von Gastrow et al 10 The importance of low sub surface plasma damage was also highlighted by Otto et al 11 In order to optimize the RIE process, we consider black Si formation consisting of three steps (even though it is a single SF 6 /O 2 plasma process): 17 (1) isotropic Si etching with fluorine radicals to form volatile SiF 4 ; (2) addition of O 2 causes a local masking layer of SiF x O y to build on the Si surface (mainly on sidewalls); and (3) etching of the SiOF passivation and Si layers. The etching process includes chemical and physical etching (ion-assisted etching).…”

Section: And A)mentioning

confidence: 96%

“…Fabrication of black Si using RIE can be achieved at cryogenic 10 as well as non-cryogenic conditions. 11,12 The cryogenic RIE process may lead to very low surface damage resulting in high effective carrier lifetime; the process is however difficult or costly to industrialize, and for that reason the non-cryogenic RIE process is preferred. In the non-cryogenic RIE process, surface damage due to energetic ion-bombardment causes a reduction of the effective carrier lifetime due to surface or near surface recombination.…”

Section: Introductionmentioning

confidence: 99%

Low surface damage dry etched black silicon

Plakhotnyuk

Gaudig

Davidsen

et al. 2017

Journal of Applied Physics

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“…In their work, aluminium oxide formed by atomic layer deposition (ALD) was used to circumvent the surface recombination issue in black silicon. Several recent studies have shown that ALD is the most suitable technique to fully cover and passivate nanostructured surfaces [21,22].…”

Section: Introductionmentioning

confidence: 99%

Passivation of all-angle black surfaces for silicon solar cells

Rahman

Bonilla

Nawabjan

et al. 2017

Solar Energy Materials and Solar Cells

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Abstract-Optical losses at the front surface of a silicon solar cell have a significant impact on efficiency, and as such, efforts to reduce reflection are necessary. In this work, a method to fabricate and passivate nanowire-pyramid hybrid structures formed on a silicon surface via wet chemical processing is presented. These high surface area structures can be utilised on the front surface of back contact silicon solar cells to maximise light absorption therein. Hemispherical reflectivity under varying incident angles is measured to study the optical enhancement conferred by these structures. The significant reduction in reflectivity (<2%) under low incident angles is maintained at high angles by the hybrid textured surface compared to surfaces textured with nanowires or pyramids alone. Finite Difference Time Domain simulations of these dual micro-nanoscale surfaces under varying angles supports the experimental results. In order to translate the optical benefit of these high surface area structures into improvements in device efficiency, they must also be well passivated. To this end, atomic layer deposition of alumina is used to reduce surface recombination velocities of these ultra-black silicon surfaces to below 30 cm/s. A decomposition of the passivation components is performed using capacitance-voltage and Kelvin Probe measurements. Finally, device simulations show power conversion efficiencies exceeding 21% are possible when using these ultra-black Si surfaces for the front surface of back contact silicon solar cells.

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Passivation of Optically Black Silicon by Atomic Layer Deposited Al2O3

Cited by 14 publications

References 13 publications

Photonic nanostructures for advanced light trapping in silicon solar cells: the impact of etching on the material electronic quality

Photonic nanostructures for advanced light trapping in silicon solar cells: the impact of etching on the material electronic quality

Low surface damage dry etched black silicon

Passivation of all-angle black surfaces for silicon solar cells

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