High hole drift mobility in a-Si:H deposited at high growth rates for solar cell application

Korevaar, BA Bas; Adriaenssens, G.J.; Smets, Ahm Arno; Kessels, Wmm Erwin; Song, Hucheng; Sanden, van de Mcm Richard; Schram, DC Daan

doi:10.1016/s0022-3093(99)00735-8

Cited by 45 publications

(16 citation statements)

References 17 publications

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“…2, the mobilities of our a-Si:H films span an order of magnitude, peaking with a mobility of ∼0.01 cm 2 /V s (similar to that observed in Ref. [16]) at the intermediate compressive stress of approximately −50 MPa, and declining rapidly on either side. We also observe that the silicon monohydride (Si-H) concentration is monotonically increasing as compressive stress increases, and that the hydrogenated void content starts to increase above its detection limit at stresses >−100 MPa.…”

Section: A Experimental Mobilitysupporting

confidence: 82%

“…Floating bonds, or overcoordinated Si atoms, showed the second largest correlation in our ensembles, while DBs contributed little to the band-tail trap states. Additional works have experimentally measured hole mobilities in deposited films over ranges of deposition conditions [14][15][16], and modeled the densities of band-tail states implied from these measurements [17][18][19][20][21]. Studies have also sought to measure densities of coordination defects experimentally, namely through electron paramagnetic resonance (EPR), although recent work has shown that such results are challenging to interpret because of the importance of the surrounding geometry on the measurement of the coordination defect [22].…”

Section: Introductionmentioning

confidence: 99%

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Hole-mobility-limiting atomic structures in hydrogenated amorphous silicon

et al. 2014

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Low hole mobility currently limits the efficiency of amorphous silicon photovoltaic devices. We explore three possible phenomena contributing to this low mobility: coordination defects, self-trapping ionization displacement defects, and lattice expansion allowing for hole wave-function delocalization. Through a confluence of experimental and first-principles investigations, we demonstrate the fluidity of the relative prevalence of these defects as film stress and hydrogen content are modified, and that the mobility of a film is governed by an interplay between various defect types.

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Section: A Experimental Mobilitysupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Hole-mobility-limiting atomic structures in hydrogenated amorphous silicon

et al. 2014

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“…13 we have illustrated experimental results for a series of a-Si:H solar cells with varying thickness, as well as the predictions of the present model for bandtail widths of 40 and 50 meV [1]. There have been several reports [25][26][27] of improvement in the hole drift-mobilities of a-Si:H. We envision that an improvement corresponding to DE V =40 meV may well be possible. As illustrated, this improvement would correspond to a power output of about 9 mW/cm 2 , but would require a 500 nm cell to exploit.…”

Section: Implications For Solar Conversion By Amorphous Siliconmentioning

confidence: 52%

03/02418 Low-mobility solar cells: a device physics primer with application to amorphous silicon

2003

Fuel and Energy Abstracts

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The properties of pin solar cells based on photogeneration of charge carriers into lowmobility materials were calculated for two models. Ideal p-and n-type electrode layers were assumed in both cases. The first, elementary case involves only band mobilities and direct electron-hole recombination. An analytical approximation indicates that the power in thick cells rises as the 1 4 power of the lower band mobility, which reflects the buildup of space-charge under illumination. The approximation agrees well with computer simulation. The second model includes exponential bandtail trapping, which is commonly invoked to account for very low hole drift mobilities in amorphous silicon and other amorphous semiconductors. The two models have similar qualitative behavior. Predictions for the solar conversion efficiency of amorphous silicon-based cells that are limited by valence bandtail trapping are presented. The predictions account adequately for the efficiencies of present a-Si : H cells in their ''asprepared'' state (without light-soaking), and indicate the improvement that may be expected if hole drift mobilities (and valence bandtail widths) can be improved. r

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“…In an effort to calibrate the hydrogen content with experimentally obtained data, a number of batch PECVD processes are conducted using varying deposition parameters; specifically, the deposition temperature in successive batches is varied which yields thin film layers with different morphologies and degrees of bonded hydrogen. Comparing the recorded values to those reported in literature [33][34][35] reveals three distinct regions of interest: (1) below 500 K the hydrogen content of the a-Si:H thin film decreases linearly with increasing deposition temperature; (2) between 500 and 575 K atomic hydrogen fractions remain relatively constant (∼9%) and (3) above 575 K the hydrogen capacity of the porous film begins to increase (see Figure 19). While the observed atomic hydrogen falls within the accepted experimental range regardless of deposition temperature, the gradual upturn of hydrogen fractions above 575 K contradicts the expected behavior.…”

Section: Steady-state Behaviormentioning

confidence: 62%

Multiscale Computational Fluid Dynamics: Methodology and Application to PECVD of Thin Film Solar Cells

2017

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This work focuses on the development of a multiscale computational fluid dynamics (CFD) simulation framework with application to plasma-enhanced chemical vapor deposition of thin film solar cells. A macroscopic, CFD model is proposed which is capable of accurately reproducing plasma chemistry and transport phenomena within a 2D axisymmetric reactor geometry. Additionally, the complex interactions that take place on the surface of a-Si:H thin films are coupled with the CFD simulation using a novel kinetic Monte Carlo scheme which describes the thin film growth, leading to a multiscale CFD model. Due to the significant computational challenges imposed by this multiscale CFD model, a parallel computation strategy is presented which allows for reduced processing time via the discretization of both the gas-phase mesh and microscopic thin film growth processes. Finally, the multiscale CFD model has been applied to the PECVD process at industrially relevant operating conditions revealing non-uniformities greater than 20% in the growth rate of amorphous silicon films across the radius of the wafer.

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High hole drift mobility in a-Si:H deposited at high growth rates for solar cell application

Cited by 45 publications

References 17 publications

Hole-mobility-limiting atomic structures in hydrogenated amorphous silicon

Hole-mobility-limiting atomic structures in hydrogenated amorphous silicon

03/02418 Low-mobility solar cells: a device physics primer with application to amorphous silicon

Multiscale Computational Fluid Dynamics: Methodology and Application to PECVD of Thin Film Solar Cells

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