Front contact optimization for rear-junction SHJ solar cells with ultra-thin n-type nanocrystalline silicon oxide

Qiu, Daohong; Duan, Weiyuan; Lambertz, Andreas; Bittkau, Karsten; Steuter, Paul; Liu, Yong; Gad, Alaaeldin; Pomaska, Manuel; Rau, Uwe; Ding, Kaining

doi:10.1016/j.solmat.2020.110471

Cited by 44 publications

(30 citation statements)

References 36 publications

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“…23 Recently, largearea (244 cm 2 ) SHJ solar cells featuring nc-SiO x :H(n) front contacts have been demonstrated with a power conversion efficiency of 23.1% (ref. 24) and a certied 25.11% efficient cell by Hanergy. 25 Achieving the aforementioned improved properties of the nc-Si:H layers during application in the SHJ solar cell, where the deposited layers' thickness is usually maintained below 10 nm, is a challenging job.…”

Section: Introductionmentioning

confidence: 99%

Nanocrystalline silicon thin film growth and application for silicon heterojunction solar cells: a short review

2021

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Section: Introductionmentioning

confidence: 99%

Nanocrystalline silicon thin film growth and application for silicon heterojunction solar cells: a short review

2021

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“…In this study we focused on the ( p )nc‐Si:H material without alloying. Alloying nc‐Si:H with oxygen 10,13,18–24 and carbon 16 is a possible way of further mitigation of the parasitic absorption loss. However, the mixing such as CO 2 44 and CH 4 45 gases during the PECVD process generally hampers the nucleation and the growth of nc‐Si:H, particularly when doped with the p ‐type dopant.…”

Section: Resultsmentioning

confidence: 99%

“…Doped hydrogenated nanocrystalline silicon (nc‐Si:H) (sometimes referred to as hydrogenated microcrystalline silicon (μc‐Si:H)) and its alloys, which feature nanometer‐sized silicon crystals embedded in an amorphous silicon (alloy) matrix, have attracted attention as an alternative carrier selective contact. This material has been used in high‐efficiency thin‐film silicon solar cells 8,9 and implemented into SHJ solar cells as a hole contact 7,10–15 and an electron contact 16–24 due to its multifunctionality such as lower parasitic absorption in the visible wavelengths and the better electrical conductivity compared with the doped a‐Si:H. Recently, doped nc‐Si:H gains more attention for application to a tunneling (recombination) layer between top and bottom cells of perovskite/Si tandem solar cells 25,26 . However, in a standard single‐junction front‐rear contacted SHJ architecture, which is the focus of the present study, it is still ambiguous whether the solar cell performance can benefit from the substitution of the conventional a‐Si:H by nc‐Si:H at the high‐efficiency level (>23%).…”

Section: Introductionmentioning

confidence: 99%

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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“…Previous studies mostly focused on reducing parasitic absorption in the front a‐Si:H layers or transparent conductive oxide (TCO) layers in the SHJ solar cells to improve J sc . [ 6–12 ] These researches mainly considered the optical losses of short‐wavelength light. In addition, all the solar cells have poor conversion efficiency for light with wavelengths near the active‐layer bandgap, where photons with energy near the bandgap can travel long distances (many times the substrate thickness) without being absorbed.…”

Section: Introductionmentioning

confidence: 99%

Improved Infrared Light Management with Transparent Conductive Oxide/Amorphous Silicon Back Reflector in High‐Efficiency Silicon Heterojunction Solar Cells

et al. 2021

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To improve the infrared (IR) response, a high‐refractive‐index intrinsic amorphous silicon (a‐Si:H) layer is introduced after metallization of bifacial silicon heterojunction (SHJ) solar cells, resulting in a transparent conductive oxide (TCO)/a‐Si:H back reflector, which functions like distributed Bragg reflector (DBR). This concept is demonstrated by both Sentaurus Technology Computer‐Aided Design (TCAD) simulation and experimental methods. The TCO/a‐Si:H back reflector can increase rear internal reflectance by reducing the transmission loss, thus improving the IR external quantum efficiency. The using of Sn‐doped In2O3 (ITO)/a‐Si:H back reflector in >23.5% efficiency SHJ solar cells can improve short‐circuit current density by 0.4 mA cm−2 which is quite similar as using the more expensive ITO/Ag back reflector, while keeping a cell bifaciality of 55%. This brings its advantage for monofacial application case. Future studies would be nice to work on higher transparent back reflectors to broaden the application in bifacial case. This back‐reflector design promotes IR response of SHJ solar cells with transferring to a wide variety of TCOs.

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Front contact optimization for rear-junction SHJ solar cells with ultra-thin n-type nanocrystalline silicon oxide

Cited by 44 publications

References 36 publications

Nanocrystalline silicon thin film growth and application for silicon heterojunction solar cells: a short review

Nanocrystalline silicon thin film growth and application for silicon heterojunction solar cells: a short review

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

Improved Infrared Light Management with Transparent Conductive Oxide/Amorphous Silicon Back Reflector in High‐Efficiency Silicon Heterojunction Solar Cells

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