Transport Losses at the TCO/a-Si:H/c-Si Heterojunction: Influence of Different Layers and Annealing

Luderer, Christoph; Messmer, Christoph; Hermle, Martin; Bivour, Martin

doi:10.1109/jphotov.2020.2983989

Cited by 38 publications

(42 citation statements)

References 41 publications

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“…Above measured resistivities are still an order of magnitude higher in comparison with the ideal values predicted by the theoretical work 42 . However, this gap might come partly from the presence of the highly‐resistive ( i )a‐Si:H layer 30 and the actual resistivity under cell operation can be lowered by illumination.…”

Section: Resultsmentioning

confidence: 72%

“…The above interpretation on the TCO/ p contact properties is evidenced by measuring the vertical hole transport using a test structure shown in Figure 10A 30 . Figure 10B shows the dark J‐V characteristics of the test structure with the thickness variation of the ( p )nc‐Si:H layer deposited by RF‐PECVD.…”

Section: Resultsmentioning

confidence: 86%

“…Contact resistivity test structures were fabricated on textured 280‐μm‐thick 3 Ωcm p ‐type FZ Si wafers. To form an ohmic contact at the single side of the wafer, a 25‐nm‐thick ( p )a‐Si:H layer (same doping type with the wafer) capped with a sputtered Ag (600 nm) was deposited on the rear side of the wafer 30 . The p‐i layers stack under investigation was deposited on the front side of the Si wafer, followed by the sputtered ITO (70 nm) and Ag (3000 nm) pads using shadow masks (8.5 × 13.0 mm 2 windows for ITO and 8.0 × 12.5 mm 2 windows for Ag).…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Nanocrystalline‐silicon hole contact layers enabling efficiency improvement of silicon heterojunction solar cells: Impact of nanostructure evolution on solar cell performance

Umishio

Sai

Koida

et al. 2020

Progress in Photovoltaics

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Hydrogenated amorphous silicon (a‐Si:H) is a key enabler in high‐efficiency crystalline silicon solar cells known as the silicon heterojunction technology. Although efforts have been devoted to replacing doped a‐Si:H contact layer by hydrogenated nanocrystalline silicon (nc‐Si:H) to take advantage of its superior optoelectrical properties, it is still unclear whether the nc‐Si:H outperforms the a‐Si:H at the high efficiency level. Here, we show that boron‐doped (p)nc‐Si:H prepared by plasma‐enhanced chemical vapor deposition (PECVD) acts as an efficient hole contact layer, providing not only a mitigation of the parasitic absorption loss but also improvements in passivation and electrical contact properties. This results in an efficiency increase by 0.3%–0.6% absolute compared to the reference cell with the (p)a‐Si:H, and a best cell efficiency of 23.54%. We find that the critical thickness of the (p)nc‐Si:H layers required for gaining high efficiency (tc ~ 15–30 nm) is a factor of 3–6 greater than that of the (p)a‐Si:H. UV Raman spectroscopy and electrical conductivity measurements reveal that the tc of the (p)nc‐Si:H is associated with the layer growth needing for the surface coalescence of nanocrystals, determining the hole selectivity and the contact resistivity at the electrode/(p)nc‐Si:H interface. Our results suggest that such nanostructure evolution can be hastened by using a very‐high‐frequency PECVD process.

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Section: Resultsmentioning

confidence: 72%

Section: Resultsmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Nanocrystalline‐silicon hole contact layers enabling efficiency improvement of silicon heterojunction solar cells: Impact of nanostructure evolution on solar cell performance

Umishio

Sai

Koida

et al. 2020

Progress in Photovoltaics

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“…As expected, dark I-V curves demonstrate the tunnel effect in the developed (n+)µc-Si:H/(p+)µc-Si:H tunnel junction and validate its high recombination efficiency. In parallel, with the method presented by Luderer et al [28], we extracted the contact resistivity of the stack (n)c-Si/(i)a-Si:H/(n)a-Si:H/(n+)µc-Si:H/(p+)µc-Si:H/ITO/Ag (front-side of the structure (c), Fig. 4) from ohmic (R² > 0.994) dark I-V curves, from -100 mV to 100 mV.…”

Section:  Tunnel Junction Behaviourmentioning

confidence: 99%

Microcrystalline Silicon Tunnel Junction for Monolithic Tandem Solar Cells Using Silicon Heterojunction Technology

Puaud

Ozanne

Senaud

et al. 2021

IEEE J. Photovoltaics

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In this study, we developed a microcrystalline silicon tunnel junction to be used as a tunnel recombination junction between a large-gap top-cell and a silicon heterojunction bottomcell, in a monolithic tandem integration. This junction is composed of a p-type layer on the top of an n-type layer, deposited by plasma-enhanced chemical vapor deposition at low temperature (200°C). Microcrystalline phase percentage was controlled with Raman spectroscopy and ellipsometry measurements. The total stack has a thickness of 40 nm and an average conductivity around 10 S/cm. Minority carrier lifetime measurements showed an improvement of the field effect and the passivation with the addition of this junction on top of silicon heterojunction solar cells. Moreover, implementation of microcrystalline layer on top of reference rear emitter silicon heterojunction solar cells improved the fill factor and did not induce parasitic absorption above 700 nm. Simple tests structures were fabricated in order to characterize the tunnel junction and optimize it. Then, we carried out dark temperature-dependent I-V measurements on those test structures and observed peaks and valleys, characteristic of the junction tunnel behavior. The developed tunnel junction shows low contact resistivity and activation energies these are promising results for the complete integration on the tandem device.

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“…Contact resistivities on the p-doped hole contact side are reported to be an order of magnitude larger. In another publication, they studied the influence of different annealing parameters on contact resistivities and found that ρ c increases originally from 28 mΩ cm 2 for annealing at 140 C to %100 mΩ cm 2 when the temperature is increased by 80 C. [11] By combining TLM results from dedicated test samples with Sun-V oc measurements of full cells, Lachenal et al [2] were able to break down the overall cell series resistance into separated contributions. They found the values of 140 and 33 mΩ cm 2 for the a-Si:H(i þ n)/TCO and TCO/Ag interfaces, respectively.…”

Section: Top Viewmentioning

confidence: 99%

Contact and Bulk Resistivity Screening for Advanced Crystalline Silicon Solar Cell Concepts by an Economical and Reliable Transfer Length Measurement Method Based on Laser Micro‐Patterning

Lange

Hensel

Hähnel

et al. 2020

Physica Status Solidi (a)

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Herein, test structures for transfer length measurements (TLMs) are prepared by means of a femtosecond laser micro‐machining process for quick and easy measurements of contact resistance and bulk resistivity in thin‐film multilayer stacks for advanced high‐efficiency silicon solar cells. In particular, silicon heterostructure layer systems composed of tin‐doped indium oxide (ITO)/n‐doped amorphous silicon (a‐Si) on crystalline silicon (c‐Si) substrates are used. To study the reliability of this novel laser‐based TLM test structure preparation method, measured data from laser structured TLM patterns are compared with conventional structures based on micro‐lithography. For small TLM test structures with contact distances between 100 and 1000 μm, the results suggest a significant dependence of the measured contact resistance values on the size of the laser prepared structures. This may be attributed to redeposited material during the laser ablation procedure at the flanks of the contact pads and insufficient mesa structuring. However, the laser and lithography‐based preparation methods yield comparable results when larger structures (contact distances between 200 and 2200 μm) are implemented. Herein, size effects can be neglected. For both methods, the specific contact resistance values of ITO/n‐doped a‐Si/c‐Si heterostructures are calculated from 8 to 45 mΩ cm2 for various samples from the same batch.

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Transport Losses at the TCO/a-Si:H/c-Si Heterojunction: Influence of Different Layers and Annealing

Cited by 38 publications

References 41 publications

Nanocrystalline‐silicon hole contact layers enabling efficiency improvement of silicon heterojunction solar cells: Impact of nanostructure evolution on solar cell performance

Nanocrystalline‐silicon hole contact layers enabling efficiency improvement of silicon heterojunction solar cells: Impact of nanostructure evolution on solar cell performance

Microcrystalline Silicon Tunnel Junction for Monolithic Tandem Solar Cells Using Silicon Heterojunction Technology

Contact and Bulk Resistivity Screening for Advanced Crystalline Silicon Solar Cell Concepts by an Economical and Reliable Transfer Length Measurement Method Based on Laser Micro‐Patterning

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