Optimization of ZnO Front Electrodes for High-Efficiency Micromorph Thin-Film Si Solar Cells

Boccard, Mathieu; Söderström, T.; Cuony, Peter; Battaglia, Corsin; Hänni, Simon; Nicolay, Sylvain; Ding, Laura; Benkhaira, M.; Bugnon, G.; Billet, Adrian; Charrière, Mathieu; Meillaud, Fanny; Despeisse, M.; Ballif, Christophe

doi:10.1109/jphotov.2011.2180514

Cited by 44 publications

(45 citation statements)

References 35 publications

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“…It is obvious that the front TCO layer has to exhibit high transparency in the useful spectrum range and a sufficient conductivity to limit the series resistance of the cell. However, it must also have sufficient surface roughness to optimize the light confinement [11]. It can be seen in Figure 1 that there is a significant difference in the surface roughness of the three TCO layers.…”

Section: Resultsmentioning

confidence: 99%

“…These nanostructured Si materials mainly include hydrogenated amorphous and microcrystalline silicon oxide (a-and μc-SiO:H) [2][3][4][5][6][7][8], protocrystalline (pc-Si:H) [9] and polymorphous (pm-Si:H) silicon [10] that could be used as alternatives to standard doped and absorber layers, respectively. On the other hand, the light trapping is mainly realized by texturing of transparent conductive oxide (TCO) layers on glass substrates [11]. However, this approach tends to deteriorate the electrical parameters of the cells with both a-and μc-Si:H absorber layers [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Substrate and p-layer effects on polymorphous silicon solar cells

et al. 2014

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The influence of textured transparent conducting oxide (TCO) substrate and p-layer on the performance of single-junction hydrogenated polymorphous silicon (pm-Si:H) solar cells has been addressed. Comparative studies were performed using p-i-n devices with identical i/n-layers and back reflectors fabricated on textured Asahi U-type fluorine-doped SnO2, low-pressure chemical vapor deposited (LPCVD) boron-doped ZnO and sputtered/etched aluminum-doped ZnO substrates. The p-layers were hydrogenated amorphous silicon carbon and microcrystalline silicon oxide. As expected, the type of TCO and p-layer both have a great influence on the initial conversion efficiency of the solar cells. However they have no effect on the defect density of the pm-Si:H absorber layer.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Substrate and p-layer effects on polymorphous silicon solar cells

et al. 2014

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“…Figure 2b shows the external quantum efficiency (EQE) spectrum of top and bottom cells for the four possible micromorph configurations employing these electrodes in front and back. The similarity of the morphology of all front electrodes is assessed by the perfect matching of the crossing of the top and bottom EQE curves for all substrates at the same wavelength (650 nm) [25]. The top cell current is only affected for such a thick cell by the front electrode (A, B and C, D are superimposed), and the higher optical band gap of the thin doped TCO layer enables a 0.2 mA cm −2 current gain.…”

Section: Resultsmentioning

confidence: 99%

“…The front and back electrodes are 2.3-µm-thick LPCVD ZnO layers with a low doping (carrier density of 2 × 10 19 ) and a high mobility (over 50 cm 2 /V/s), resulting in a sheet resistance below 30 Ω/ for a high transparency as seen in Figure 2a [25]. The thickness of the intrinsic layer of the a-Si:H top cell is 230 nm, and the thickness of the intrinsic layer of the µc-Si:H bottom cell is 2.3 µm.…”

Section: Resultsmentioning

confidence: 99%

The role of front and back electrodes in parasitic absorption in thin-film solar cells

et al. 2014

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When it comes to parasitic absorption in thin-film silicon solar cells, most studies focus on one electrode only, most of the time the substrate (in n-i-p configuration) or superstrate (in p-i-n configuration). We investigate here simultaneously the influence of the absorption in both front and back electrodes on the current density of tandem micromorph solar cells in p-i-n configuration. We compare four possible combinations of front and back electrodes with two different doping levels, but identical sheet resistance and identical light-scattering properties. In the infrared part of the spectrum, parasitic absorption in the front or back electrode is shown to have a similar effect on the current generation in the cell, which is confirmed by modeling. By combining highly transparent front and back ZnO electrodes and high-quality silicon layers, a micromorph device with a stabilized efficiency of 11.75% is obtained.

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“…The most common TCOs used as front electrodes for TF-Si solar cells in the superstrate (p-i-n) configuration are aluminum-doped zinc oxide (ZnO:Al) deposited by sputtering [12,13], boron-doped zinc oxide (ZnO:B) grown by low-pressure chemical vapor deposition (LPCVD) [14] and fluorine-doped tin oxide (SnO 2 :F) grown by atmospheric-pressure chemical vapor deposition (APCVD) [15,16].…”

Section: Introductionmentioning

confidence: 99%

Highly transparent front electrodes with metal fingers for p-i-n thin-film silicon solar cells

et al. 2015

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The optical and electrical properties of transparent conductive oxides (TCOs), traditionally used in thin-film silicon (TF-Si) solar cells as front-electrode materials, are interlinked, such that an increase in TCO transparency is generally achieved at the cost of reduced lateral conductance. Combining a highly transparent TCO front electrode of moderate conductance with metal fingers to support charge collection is a well-established technique in wafer-based technologies or for TF-Si solar cells in the substrate (n-i-p) configuration. Here, we extend this concept to TF-Si solar cells in the superstrate (p-i-n) configuration. The metal fingers are used in conjunction with a millimeter-scale textured foil, attached to the glass superstrate, which provides an antireflective and retroreflective effect; the latter effect mitigates the shadowing losses induced by the metal fingers. As a result, a substantial increase in power conversion efficiency, from 8.7% to 9.1%, is achieved for 1-µm-thick microcrystalline silicon solar cells deposited on a highly transparent thermally treated aluminum-doped zinc oxide layer combined with silver fingers, compared to cells deposited on a state-of-the-art zinc oxide layer.

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Optimization of ZnO Front Electrodes for High-Efficiency Micromorph Thin-Film Si Solar Cells

Cited by 44 publications

References 35 publications

Substrate and p-layer effects on polymorphous silicon solar cells

Substrate and p-layer effects on polymorphous silicon solar cells

The role of front and back electrodes in parasitic absorption in thin-film solar cells

Highly transparent front electrodes with metal fingers for p-i-n thin-film silicon solar cells

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