Deposition of intrinsic hydrogenated amorphous silicon for thin-film solar cells - a comparative study for layers grown statically by RF-PECVD and dynamically by VHF-PECVD

Zimmermann, T.; Flikweert, A.J.; Merdzhanova, Tsvetelina; Woerdenweber, J.; Gordijn, A.; Rau, Uwe; Stahr, F.; Dybek, K.; Bartha, Johann W.

doi:10.1002/pip.2254

Cited by 6 publications

(4 citation statements)

References 23 publications

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Section: ■ Results and Discussionmentioning

confidence: 99%

“…The MoO 3 thin films were deposited as a p-type layer on textured FTO glass through thermal evaporation or sputtering with gaseous Ar alone in the absence of O 2 . The subsequent intrinsic layer and LiF/Al were deposited using VHF-PECVD to obtain a high-quality thin-film Si layer (and not by radio frequency (RF)-PECVD)37 and thermal evaporation, respectively.Figure1bshows the energy band diagram of the proposed dopant-free solar cell. Even though MoO 3 is an n-type material, its Fermi level is well-matched with that of FTO, and hence MoO 3 can provide an adequate V bi with the LiF n-type layer.…”

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confidence: 99%

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Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

et al. 2013

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Toxic doping gases are usually used to produce hydrogenated amorphous silicon (a-Si:H) layers in thin-film solar cells (TFSCs). Hence, an alternative structure that avoids the use of toxic gases is desirable. In this work, we replaced both the p-type-a-Si:H and n-type-a-Si:H layers simultaneously in a normal TFSC to form a structure that is dopant-free. Molybdenum oxide (MoO3) and lithium fluoride were used as the p-type and n-type layers, respectively. The effects of the deposition method and the thickness of the MoO3 layer on the device performance were investigated. The power-conversion efficiency of the optimized hybrid solar cell reached a maximum of 7.08%, which is remarkable considering the novel structure of the dopant-free devices. The light stability of the devices with and without MoO3 was also compared: the light stability of the device with MoO3 was found to be much better than that of the device without MoO3 and with p-i-n Si layers. This was ascribed to the insignificant number of defect sites generated by the nondoping elements, which led to a less contaminated, more compact, and smoother oxide surface, resulting in an increase in the electron lifetime and improved light stability. This work opens up a new direction toward the development of a truly dopant-free device that does not involve the use of toxic gases during fabrication and provides the potential for further enhancement of the efficiency of future dopant-free solar cells.

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Section: ■ Results and Discussionmentioning

confidence: 99%

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confidence: 99%

Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

et al. 2013

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“…Zimmermann et al investigated the difference between in‐line and batch process deposition of i‐a‐Si:H for thin film p–i–n type solar cells. They found no significant difference in solar cell performance between the two process types.…”

Section: Introductionmentioning

confidence: 99%

Comparison of batch and in‐line PECVD of a‐Si:H passivation layers for silicon heterojunction solar cells

Landheer

Kaiser

Poulios

et al. 2016

Physica Rapid Research Ltrs

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We present PECVD deposition of i‐a‐Si:H in an in‐line configuration for the fabrication of silicon heterojunction solar cells. For industry, in‐line processing has the potential to increase production throughput and yield. We compared batch and in‐line fabrication of i‐a‐Si:H passivation samples with identical plasma conditions and observed that the a‐Si:H material properties do not significantly differ. In batch‐type production the substrate is in the plasma zone at the moment of ignition, whereas for in‐line deposition the substrate is introduced into the plasma zone when steady plasma conditions have been reached. Our preliminary results show that there are depositions conditions that result both for in‐line and batch‐type deposition in good i‐a‐Si:H passivation layers. Therefore both methods can equally well be considered for the production of silicon heterojunction solar cells. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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“…Earlier work demonstrated that we can deposit state-ofthe-art a-Si:H solar cells by dynamic VHF-PECVD. 9 Our current study focuses on deposition of microcrystalline silicon, since its properties are more sensitive to changing deposition Continued on next page…”

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Dynamic deposition of microcrystalline silicon

Zimmermann¹,

Merdzhanova²,

Gordijn³

et al. 2013

SPIE Newsroom

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Combining linear plasma sources and high-frequency plasma deposition on moving substrates may reduce manufacturing costs for thin-film silicon solar cells. The first solar cells made of microcrystalline silicon (c-Si:H) were successfully deposited in 1994. 1 Since then, single-junction p-in solar cells made with this particular material have achieved efficiencies of greater than 10%. 2 To compete with other photovoltaic technologies, however, the microcrystalline silicon cell is often combined with an amorphous silicon (a-Si:H) cell in an a-Si:H/ c-Si:H tandem junction device. This improves the conversion efficiency of the cell, and therefore the voltage of the device, compared with single-junction solar cells. Amorphous and microcrystalline silicon layers are typically deposited using plasma-enhanced chemical vapor deposition (PECVD). The c-Si:H absorber layer represents about 80% of the total silicon layer thickness of an a-Si:H/ c-Si:H tandem solar cell. As a result, its deposition rate has a significant influence on the throughput of the PECVD equipment and the manufacturing costs. Therefore, research into thin-film silicon growth aims to achieve high deposition rates for c-Si:H. Developers have found that microcrystalline silicon solar cells deposited by radio-frequency (RF) and very-high frequency (VHF) PECVD processes both obtain efficiencies of about 9-10%. However, RF-PECVD processes are carried out at deposition rates of 0.5nm/s to maintain good material quality. 3 In contrast, VHF-PECVD processes can be conducted at deposition rates up to about 2.5nm/s with little influence on the solar cell performance. 4 While very high frequencies are beneficial for the quality of c-Si:H grown at high rates, they have a negative influence on the homogeneity of the deposition process when using large/industrial-scale electrodes. Developers have proposed various solutions to this problem, 5-7 all of them targeting static deposition processes, where the substrate remains stationary in front of the electrode during deposition.

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Deposition of intrinsic hydrogenated amorphous silicon for thin-film solar cells - a comparative study for layers grown statically by RF-PECVD and dynamically by VHF-PECVD

Cited by 6 publications

References 23 publications

Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

Comparison of batch and in‐line PECVD of a‐Si:H passivation layers for silicon heterojunction solar cells

Dynamic deposition of microcrystalline silicon

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