High efficiency high rate microcrystalline silicon thin-film solar cells deposited at plasma excitation frequencies larger than 100 MHz

Strobel, C.; Leszczynska, B.; Merkel, U.; Kuske, J.; Fischer, D.; Albert, Matthias; Holovský, Jakub; Michard, S.; Bartha, Johann W.

doi:10.1016/j.solmat.2015.07.014

Cited by 15 publications

(6 citation statements)

References 33 publications

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confidence: 86%

“…14 Using plasma excitation frequencies larger than 100 MHz is a unique feature in the field of PECVD methods. 15 Beneficial effects of using 140 MHz PECVD compared to lower frequencies were already demonstrated by Leszczynska et al for thin-film silicon solar cells. 16 Here, we show that in contrast to the conventional radio frequency (RF, 13.56 MHz) PECVD a very high frequency (VHF, 140 MHz) PECVD can be used to cover CVD graphene with thin a-Si:H layers very softly without changing the properties of the underlying graphene significantly.…”

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confidence: 86%

“…Before Si deposition samples were annealed in UHV at 400°C for 20 min to remove residual polymer used as a support in the transfer process. To deposit thin a-Si:H layers on transferred graphene we used 140 MHz excitation 15 to exploit the ion energy reduction potential of VHF PECVD as much as possible. For comparison, a-Si:H layers of the same thickness (20 nm and 30 nm) were deposited also by conventional RF PECVD.…”

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confidence: 99%

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Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

Łupina

Strobel

Dąbrowski

et al. 2016

Applied Physics Letters

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Plasma-enhanced chemical vapor deposition of thin a-Si:H layers on transferred large area graphene is investigated. Radio frequency (RF, 13.56 MHz) and very high frequency (VHF, 140 MHz) plasma processes are compared. Both methods provide conformal coating of graphene with Si layers as thin as 20 nm without any additional seed layer. The RF plasma process results in amorphization of the graphene layer. In contrast, the VHF process keeps the high crystalline quality of the graphene layer almost intact. Correlation analysis of Raman 2D and G band positions indicates that Si deposition induces reduction of the initial doping in graphene and an increase of compressive strain. Upon rapid thermal annealing the amorphous Si layer undergoes dehydrogenation and transformation into a polycrystalline film whereby a high crystalline quality of graphene is preserved.Ability to deposit uniform thin layers of insulators and semiconductors on graphene is of crucial importance for many envisioned applications of this material in advanced electronic and photonic devices.1 Si-graphene junctions are particularly interesting for graphene-based photodetectors, sensors, and high-frequency vertical heterojunction transistors.

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confidence: 86%

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confidence: 99%

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Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

Łupina

Strobel

Dąbrowski

et al. 2016

Applied Physics Letters

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“…In the following, 160 nm thick n-type a-Si:H was locally deposited on top of the structure by VHF-PECVD (140 MHz). A deterioration of the graphene layer quality due to the silicon deposition can be excluded according to previous investigations .…”

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confidence: 99%

Novel Graphene Adjustable-Barrier Transistor with Ultra-High Current Gain

Strobel

Chavarin

Richter

et al. 2022

ACS Appl. Mater. Interfaces

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A graphene-based three-terminal barristor device was proposed to overcome the low on/off ratios and insufficient current saturation of conventional graphene field-effect transistors. In this study, we fabricated and analyzed a novel graphene-based transistor, which resembles the structure of the barristor but uses a different operating condition. This new device, termed graphene adjustable-barriers transistor (GABT), utilizes a semiconductor-based gate rather than a metal–insulator gate structure to modulate the device currents. The key feature of the device is the two graphene-semiconductor Schottky barriers with different heights that are controlled simultaneously by the gate voltage. Due to the asymmetry of the barriers, the drain current exceeds the gate current by several orders of magnitude. Thus, the GABT can be considered an amplifier with an alterable current gain. In this work, a silicon–graphene–germanium GABT with an ultra-high current gain (I D/I G up to 8 × 106) was fabricated, and the device functionality was demonstrated. Additionally, a capacitance model is applied to predict the theoretical device performance resulting in an on–off ratio above 106, a swing of 87 mV/dec, and a drive current of about 1 × 106 A/cm2.

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“…The visibility in the EQE spectrum is even more reduced due to poor carrier collection from these defects. It is well known that, although “cracks” in μc-Si − might be effectively invisible in the EQE, they still reduce the V OC considerably. The proportionality between radiative recombination and optical absorption is lost in such cases.…”

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confidence: 99%

Below the Urbach Edge: Solar Cell Loss Analysis Based on Full External Quantum Efficiency Spectra

et al. 2023

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We suggest a new solar cell loss analysis using the external quantum efficiency (EQE) measured with sufficiently high sensitivity to also account for defects. Unlike common radiative-limit methods, where the impact of deep defects is ignored by exponential extrapolation of the Urbach absorption edge, our loss analysis considers the full EQE including states below the Urbach edge and uses corrections for band-filling and light-trapping. We validate this new metric on a whole range of photovoltaic materials and verify its accuracy by electrical simulations. Any deviations between the new metric and experimental open-circuit voltage are due to the presence of spatially localized defects and are explained as violations of the assumption of flat quasi-Fermi levels through the device.

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High efficiency high rate microcrystalline silicon thin-film solar cells deposited at plasma excitation frequencies larger than 100 MHz

Cited by 15 publications

References 33 publications

Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

Novel Graphene Adjustable-Barrier Transistor with Ultra-High Current Gain

Below the Urbach Edge: Solar Cell Loss Analysis Based on Full External Quantum Efficiency Spectra

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