Band lineup in amorphous/crystalline silicon heterojunctions and the impact of hydrogen microstructure and topological disorder

Schulze, T. F.; Korte, Lars; Ruske, F.; Rech, Bernd

doi:10.1103/physrevb.83.165314

Cited by 100 publications

(83 citation statements)

References 62 publications

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“…The valence band of the thermally converted layers is closer to the Fermi level than for the PECVD layer and moves even closer with increasing conversion temperature. This is consistent with a lower hydrogen content in these layers and a further decrease of it, with increasing conversion temperature 23 . Moreover a low hydrogen content is supposedly detrimental to the electronic quality of a-Si:H. The second parameter extracted from CFSYS data is the valence tail Urbach energy.…”

supporting

confidence: 70%

“…In contrast the structural bulk quality is less important for surface passivation layers. Passivation of crystalline silicon with a-Si:H relies on two mechanisms: Formation of an atomically sharp a-Si:H/cSi-interface consisting mainly of Si-Si bonds and saturation of the remaining dangling bonds with hydrogen provided during and after the a-Si:H deposition 23 . The neopentasilane precursor transforms into a-Si:H by Si-H bond breaking and formation of Si-Si-bonds.…”

mentioning

confidence: 99%

“…It is a measure of electronic and structural disorder in a-Si:H, since the valence band tail consists of Si-Si-binding states with bond lengths and angles deviating from the eqilibrium 24 . In general a low Urbach energy of about 60 meV is considered favorable for application of a-Si:H in electronic devices 23 . The PECVD reference layer exhibits an Urbach energy of about 55 meV (Fig.…”

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confidence: 99%

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Solution-processed amorphous silicon surface passivation layers

Mews

Mader

Traut

et al. 2014

Applied Physics Letters

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Amorphous silicon thin films, fabricated by thermal conversion of neopentasilane, were used to passivate crystalline silicon surfaces. The conversion is investigated using X-ray and constant-final-state-yield photoelectron spectroscopy, and minority charge carrier lifetime spectroscopy. Liquid processed amorphous silicon exhibits high Urbach energies from 90 to 120 meV and 200 meV lower optical band gaps than material prepared by plasma enhanced chemical vapor deposition. Applying a hydrogen plasma treatment, a minority charge carrier lifetime of 1.37 ms at an injection level of 10 15 /cm 3 enabling an implied open circuit voltage of 724 mV was achieved, demonstrating excellent silicon surface passivation.

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supporting

confidence: 70%

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confidence: 99%

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confidence: 99%

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Solution-processed amorphous silicon surface passivation layers

Mews

Mader

Traut

et al. 2014

Applied Physics Letters

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“…Simulation results indicate that to achieve a flat LBIC profile for a 2 Â 2 mm 2 cell, the acceptor doping in the a-Si:H(p) layer would have to be increased tenfold and the valence band offset would have to be higher than 2.6 eV, leading to strong inversion in the c-Si. Such high offsets cannot be achieved in practice with a-Si:H, 34 but might be possible with other materials.…”

Section: Resultsmentioning

confidence: 91%

“…18 In practice, the DE vb can be increased by 0.15 eV by increasing the a-Si:H hydrogen content from 12% to 24%. 34 Another possibility is to deposit hydrogenated amorphous silicon suboxide films (a-SiO x :H) with higher bandgaps than a-Si:H. 35,36 In the simulations, the initial DE vb of 0.43 eV was varied by hypothetically changing the front a-Si:H layers' bandgap, while leaving all other parameters the same. Note that widening the bandgap of the emitter and front intrinsic a-Si:H layers would also decrease the UV and visible parasitic absorption in these layers.…”

Section: Resultsmentioning

confidence: 99%

Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells

Filipič

Holman

Smole

et al. 2013

Journal of Applied Physics

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In amorphous/crystalline silicon heterojunction solar cells, an inversion layer is present at the front interface. By combining numerical simulations and experiments, we examine the contribution of the inversion layer to lateral transport and assess whether this layer can be exploited to replace the front transparent conductive oxide (TCO) in devices. For this, heterojunction solar cells of different areas (2 Â 2, 4 Â 4, and 6 Â 6 mm 2 ) with and without TCO layers on the front side were prepared. Laser-beam-induced current measurements are compared with simulation results from the ASPIN2 semiconductor simulator. Current collection is constant across millimeter distances for cells with TCO; however, carriers traveling more than a few hundred microns in cells without TCO recombine before they can be collected. Simulations show that increasing the valence band offset increases the concentration of holes under the surface of n-type crystalline silicon, which increases the conductivity of the inversion layer. Unfortunately, this also impedes transport across the barrier to the emitter. We conclude that the lateral conductivity of the inversion layer may not suffice to fully replace the front TCO in heterojunction devices. V C 2013 AIP Publishing LLC.

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Dislocations in Crystalline Silicon Solar Cells

Wang,

Liu,

et al. 2023

Adv Energy and Sustain Res

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Dislocation is a common extended defect in crystalline silicon solar cells, which affects the recombination characteristics of solar cells by forming deep‐level defect states in the silicon bandgap, thereby reducing the lifetime of minority carrier. Hence, reducing the impact of defects on device performance is an effective strategy to optimize the performance of photovoltaic devices. This article reviews the observation and engineering of dislocation in Si solar cell. The structure and deformation of Si can be directly observed by chemical etching combined with electron microscopy. Also, more information about dislocation is obtained indirectly by monitoring the electrical and optical properties of Si. The classification, density, distribution of dislocations, and their interactions with other defects in Si can affect the lifetime of minority carriers and thereby reduce the performance of Si solar cells. In order to achieve higher cell efficiency, crystals with less or even no dislocation should be obtained. In addition to the specification of controlling the relevant parameters during the growth of silicon ingots to obtain the minimum dislocation density, it is necessary to study the behavior of dislocation in Si wafers under the combined action of external stress, temperature, and other defects.

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Band lineup in amorphous/crystalline silicon heterojunctions and the impact of hydrogen microstructure and topological disorder

Cited by 100 publications

References 62 publications

Solution-processed amorphous silicon surface passivation layers

Solution-processed amorphous silicon surface passivation layers

Analysis of lateral transport through the inversion layer in amorphous silicon/crystalline silicon heterojunction solar cells

Dislocations in Crystalline Silicon Solar Cells

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