Lateral transport in silicon solar cells

Haschke, Jan; Christmann, Gabriel; Messmer, Christoph; Bivour, Martin; Boccard, Mathieu; Ballif, Christophe

doi:10.1063/1.5139416

Cited by 34 publications

(25 citation statements)

References 44 publications

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“…Indeed, restricting the rear metal contact fraction increases the series resistance due to the rear contact resistance ( R S,contact ≈ ρ c /metal contact fraction) and the lateral resistance in the n‐Si substrate ( R S,lateral ). [ 36 ] Note that conversely, as the whole rear side was in contact with the metallic measurement chuck, R S,finger is not expected to contribute to R S,total (similarly to a “busbarless” measurement) for any finger width. The increase in series resistance is obvious in Figure a,b shows the series resistance extracted from two‐diode fits of the data, confirming this interpretation.…”

Section: Resultsmentioning

confidence: 99%

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Dopant‐Free Bifacial Silicon Solar Cells

et al. 2021

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Herein, challenges in the fabrication of full dopant‐free bifacial silicon solar cells are discussed and efficient devices utilizing a MoO3/ indium tin oxide (ITO)/Ag hole‐selective contact and ZnO/LiFx/Al electron‐selective contacts with up to 79% short‐circuit current bifaciality are demonstrated. The ZnO/LiFx/Al rear electron contact features a full‐area ZnO antireflective coating and a LiFx/Al finger contact, allowing sunlight absorption from the back side, thus producing more overall power. The ZnO/LiFx/Al electron contacts with a thinner ZnO layer and a larger contact fraction display a better selectivity and a lower resistance loss. When considering rear‐side irradiance of 0.15 sun, the dopant‐free bifacial solar cell with 60 nm ZnO and 50% LiFx/Al metal contact fraction achieves a 3% estimated output power density improvement compared with its monofacial counterpart (21.0 mW cm−2 compared to 20.3 mW cm−2) using the full‐area back contact. Both the efficiency and bifaciality factor of this dopant‐free device are still significantly lower than those of state‐of‐the‐art devices relying on doped‐silicon‐based layers. The required improvement for this technology to become industry‐relevant is discussed.

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Section: Resultsmentioning

confidence: 99%

“…We performed simulations using the framework developed in Haschke et al [ 36 ] to quantitatively evaluate how the different rear metallization patterns affect R S,contact and R S,lateral for different values of contact resistance from 0.1 to 0.4 Ω cm 2 . The range of variation is shown in Figure 3 as the orange areas.…”

Section: Resultsmentioning

confidence: 99%

Dopant‐Free Bifacial Silicon Solar Cells

et al. 2021

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“…They found the values of 140 and 33 mΩ cm 2 for the a‐Si:H(i + n)/TCO and TCO/Ag interfaces, respectively. Haschke et al [ 12 ] investigated the lateral charge carrier transport in HJT solar cells under typical operating illumination conditions comparing simulations and experimental results. They found that the coupling contact resistance needs to be low to benefit from lateral current flow in the silicon absorber and reported the values lower than 300 mΩ cm 2 for the p‐contacts in their devices.…”

Section: Resultsmentioning

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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“…This shows that in addition to ρ c also R sheet was sufficiently low using O 2 -rich ITO in combination with low-oxygen ITO interlayer. It is important to mention that lateral transport is not only provided by the TCO, but also by the silicon absorber [46]. The distribution of lateral transport between absorber and TCO is determined by ρ c and efficient coupling is only possibly with low ρ c .…”

Section: E Shj Solar Cells With Ito Stackmentioning

confidence: 99%

Influence of TCO and a-Si:H Doping on SHJ Contact Resistivity

Luderer

Tutsch

Messmer

et al. 2021

IEEE J. Photovoltaics

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Resistive losses in silicon heterojunction (SHJ) solar cells are partly linked to transport barriers at the amorphous silicon/crystalline silicon (a-Si:H/c-Si) and transparent conductive oxide (TCO)/a-Si:H interfaces. A key parameter is the position of the Fermi-level on either side of the junction which we modify by a systematic doping variation of the amorphous silicon and the transparent conductive oxide. We identify the charge carrier concentration to be the main driver for low contact resistance. For a-Si:H, this is achieved by using a sufficient but not too high doping gas concentration during deposition. For indium tin oxide (ITO) and aluminum zinc oxide (AZO), no or only a very low oxygen (O 2 ) gas concentration during deposition is needed. We show that a stack of low-oxygen ITO interlayer and an oxygen-rich ITO "bulk" layer is not only an effective means to combine efficient transport and low TCO absorption but also to improve the thermal stability of the a-Si:H/TCO/metal contact resistivity (ρ c ). Such a layer stack helps to relax the constraints regarding the optoelectrical performance and improves the efficiency of SHJ solar cells.

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Lateral transport in silicon solar cells

Abstract: We investigate lateral charge carrier transport in crystalline silicon solar cells. Under typical operation illumination of high efficiency solar cells, a significant population of electrons and holes

Cited by 34 publications

References 44 publications

Dopant‐Free Bifacial Silicon Solar Cells

Dopant‐Free Bifacial Silicon Solar Cells

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

Influence of TCO and a-Si:H Doping on SHJ Contact Resistivity

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