Distribution of hydrogen in low temperature passivated amorphous silicon (a-Si:H) films from neutron reflectivity

Vogt, Bryan D.; O’Brien, Barry; Allee, David R.; Loy, Doug; Akgün, Bülent; Satija, Sushil K.

doi:10.1016/j.jnoncrysol.2010.11.030

Cited by 4 publications

(2 citation statements)

References 31 publications

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“…Using the high hydrogen dilutions is possibly essential in achieving a high passivation degree of hydrogen of the silicon bonds in the volume deficiencies. [17] The deposition rate is maintained for the strong hydrogen diluted conditions when compared to deposition from pure silane (~15 nm/min) at low pressures. For the "protocrystalline" deposition regime the deposition rate typically quenches to below 5 nm/min.…”

Section: Methodsmentioning

confidence: 99%

Degradation kinetics of amorphous silicon solar cells processed at high pressure and its relation to the nanostructure

Fischer

Quax

Zeman

et al. 2013

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) PART 2

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In this study it is revealed that the light induced defects (LIDs) responsible for the fast degradation of hydrogenated amorphous silicon (a-Si:H) solar cells under light soaking are located at nanosized voids. This important breakthrough in identifying the local environment of LIDs has been achieved by detailed study of the relation between the nanostructure of a-Si:H and metastability of corresponding solar cell devices under light soaking. We propose that a useful tool to define the nanostructure of a-Si:H is to determine the size distribution of the volume deficiencies, which range from small hydrogenated vacancies up to nanosized voids. The processing window used to vary and control the nanostructure in dense a-Si:H is based on a hydrogen rich plasma at unconventional high processing pressures (~10 mbar). The dense absorber layers with different distributions of volume deficiencies are subsequently incorporated in solar cell devices. For the first time a clear relation between nanostructures of the a-Si:H absorber layer and the fast kinetics of the metastable LIDs of the solar cell during light soaking and thermal annealing is observed. The 'fast' degradation (first 10 hours of light soaking) strongly correlates to the density of largest volume deficiencies in the a-Si:H matrix.The "slow" regime (10 tot 1000 hours of light soaking) appears to be independent on the nanostructure of the absorber layer. In addition, the fast metastable defect states are the first ones to be annealed out at relative low annealing temperatures (120-130 C). Although solar cells processed at higher pressure have the same long term degradation kinetics, their FF recovers much faster by thermal annealing when compared to the cells processed at standard low pressure and low hydrogen dilution conditions. Index Terms -amorphous silicon materials, light induced degradation, metastability, photovoltaic cells, nanostructure, staebler-wronski.

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Section: Methodsmentioning

confidence: 99%

Degradation kinetics of amorphous silicon solar cells processed at high pressure and its relation to the nanostructure

Fischer

Quax

Zeman

et al. 2013

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) PART 2

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“…Oxygen acts as an acceptor in OSCs and its states distribute along the edge of the HOMO. Primarily, oxygen doping pre-empties the donor-like trap states 32 induced by static/dynamic disorder or other factors 33 (i.e., it releases the E F pinning) and thus yields mobile hole carriers in the HOMO (i.e., it renders the E F close to the edge of the HOMO), which is in analogy to the role of hydrogen in a -Si 34 . Meanwhile, the width of depletion layer and the height of the Schottky barrier at the metal/semiconductor interfaces is reduced due to the oxygen doping, which facilitates carrier injection through thermionic emission (TE) and thermionic field emission (TFE) 35 .…”

Section: Resultsmentioning

confidence: 99%

Unraveling the crucial role of trace oxygen in organic semiconductors

Huang,

Wu,

Sun

et al. 2024

Nat Commun

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Optoelectronic properties of semiconductors are significantly modified by impurities at trace level. Oxygen, a prevalent impurity in organic semiconductors (OSCs), has long been considered charge-carrier traps, leading to mobility degradation and stability problems. However, this understanding relies on the conventional deoxygenation methods, by which oxygen residues in OSCs are inevitable. It implies that the current understanding is questionable. Here, we develop a non-destructive deoxygenation method (i.e., de-doping) for OSCs by a soft plasma treatment, and thus reveal that trace oxygen significantly pre-empties the donor-like traps in OSCs, which is the origin of p-type characteristics exhibited by the majority of these materials. This insight is completely opposite to the previously reported carrier trapping and can clarify some previously unexplained organic electronics phenomena. Furthermore, the de-doping results in the disappearance of p-type behaviors and significant increase of n-type properties, while re-doping (under light irradiation in O2) can controllably reverse the process. Benefiting from this, the key electronic characteristics (e.g., polarity, conductivity, threshold voltage, and mobility) can be precisely modulated in a nondestructive way, expanding the explorable property space for all known OSC materials.

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Thin-film optical function acquisition from experimental measurements of the reflectance and transmittance spectra: a case study

Moghaddam

Cheung

Noël

et al. 2021

J Mater Sci: Mater Electron

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Distribution of hydrogen in low temperature passivated amorphous silicon (a-Si:H) films from neutron reflectivity

Cited by 4 publications

References 31 publications

Degradation kinetics of amorphous silicon solar cells processed at high pressure and its relation to the nanostructure

Degradation kinetics of amorphous silicon solar cells processed at high pressure and its relation to the nanostructure

Unraveling the crucial role of trace oxygen in organic semiconductors

Thin-film optical function acquisition from experimental measurements of the reflectance and transmittance spectra: a case study

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