Non-Gaussian Transport Measurements and the Einstein Relation in Amorphous Silicon

Gu, Qing; Schiff, E. A.; Grebner, S.; Wang, F.; Schwarz, R.

doi:10.1103/physrevlett.76.3196

Cited by 179 publications

(108 citation statements)

References 14 publications

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“…(9) Gu, et al [33] reported that this prediction agreed fairly well with measurements for a-Si:H, which is thus an experimental confirmation of the generalized Einstein relation.…”

Section: Appendix 2: Connecting the 7-parameter Model With Steady-stasupporting

confidence: 73%

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Carrier drift-mobilities and solar cell models for amorphous and nanocrystalline silicon

Schiff

2009

MRS Proc.

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Hole drift mobilities in hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) are in the range of 10 -3 to 1 cm 2 /Vs at room-temperature. These low drift mobilities establish corresponding hole mobility limits to the power generation and useful thicknesses of the solar cells. The properties of as-deposited a-Si:H nip solar cells are quite close to their hole mobility limit, but the corresponding limit has not been examined for nc-Si:H solar cells. We explore the predictions for nc-Si:H solar cells based on parameters and values estimated from hole drift-mobility and related measurements. The indicate that the hole mobility limit for nc-Si:H cells corresponds to an optimum intrinsic-layer thickness of 2-3 µm, whereas the best nc-Si:H solar cells (10% conversion efficiency) have thicknesses around 2 µm.

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“…(9) Gu, et al [33] reported that this prediction agreed fairly well with measurements for a-Si:H, which is thus an experimental confirmation of the generalized Einstein relation.…”

Section: Appendix 2: Connecting the 7-parameter Model With Steady-stasupporting

confidence: 73%

“…where F is the electric field; we have also used the detailed balance relation There is a "generalized Einstein relation" connecting this drift with diffusion of a carrier [33]; the root-mean-square width L D of an initially narrow distribution is related to L drift as:…”

Section: Appendix 2: Connecting the 7-parameter Model With Steady-stamentioning

confidence: 99%

Carrier drift-mobilities and solar cell models for amorphous and nanocrystalline silicon

Schiff

2009

MRS Proc.

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“…Hexagon -"triode" a-Si:H (Ganguly, et al, 1996). Square -a-Si:H (Gu, et al, 1996). Triangle -aSi:H (Tiedje, et al, 1984).…”

Section: Relationship Of Ambipolar Diffusion Length Measurements and unclassified

“…1994 for details; the actual measurements are presented in Gu, Schiff, Grebner, Wang, and Schwarz, 1996). In particular we evaluate as D L h amb R = 2 2 / τ , where L amb is the ambipolar diffusion length actually measured by SSPG and τ R is the recombination response time measured from the photoconductivity decay time.…”

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Research on High-Bandgap Materials and Amorphous Silicon-Based Solar Cells, Final Technical Report, 15 May 1994-15 January 1998

Schiff¹,

Gu²,

Lin³

et al. 1998

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or DOE Information Bridge http://www.doe.gov/bridge/home.html Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste 1 Preface This research project had four broad objectives involving a variety of technical approaches:• We sought a deeper understanding of the open circuit voltage V OC in amorphous silicon based solar cells, and in particular for cells employing wide bandgap modification of amorphous silicon as their absorber layer. Our technical approach emphasized the development of electroabsorption measurements as a tool for probing the built-in potential of a-Si:H based solar cells.• We sought a better understanding of the optical properties of amorphous silicon and of microcrystalline silicon materials such as used in the p + layer of some advanced a-Si:H based solar cells. Electroabsorption spectroscopy appears to be useful for this purpose, and was a natural extension of the built-in potential research.• We sought to improve our understanding of the fundamental electron and hole photocarrier transport processes in the materials used for amorphous silicon based solar cells. Our technical approach was been to develop photocarrier time-of-flight measurements in solar cells.• We aimed to improve V OC in wide bandgap cells by searching for superior materials for the p-type "window layer" of the cell, and explored thin-film boron phosphide for this purpose.In addition to the authors of this report, we have reported work which includes the contributions of several collaborators, in particular Reinhard Schwarz, Stefan Grebner, and We have also benefitted from the cooperation and interest of several other scientists and organizations. In particular we thank Christopher Wronski at Pennsylvania State University, Steve Hegedus at the Institute of Energy Conversion, University of Delaware, and Murray Bennett at Solarex Corp. Thin Films Division. Summary• The built-in potential is a crucial device parameter for solar cells, and one which is only roughly known and understood for a-Si:H based cells. We have developed a technique based on electroabsorption measurements for obtaining quantitative estimates of the built-in potential in aSi:H based heterostructure solar cells incorporating microcrystalline or a-SiC:H p layers. This heterostructure problem has been a major limitation in application of the electroabsorption technique. The new technique only utilizes measurements from a particular solar cell, and is thus a significant improvement on earlier techniques requiring measurements on auxiliary films.• Using this new electroabsorption technique, we confirmed previous estimates of V bi ≈ 1.0 V in a-Si:H solar cells with "conventional" intrinsic layers and either microcrystalline or a-SiC:H p layers. Interestingly, our measurements on high V oc cells grown with "high hydrogen dilution" intrinsic layers yield a much larger value for V bi ≈ 1.3 V. We speculate that these results are evidence for a 2 significant interface dipole at the p/i heterostructure interface. Although we believe that i...

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Description of Charge Transport in Amorphous Semiconductors

Baranovski

Rubel

2006

Charge Transport in Disordered Solids With Applications in Electronics

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2.1 Introduction 2.2 General Remarks on Charge Transport in Disordered Materials 2.3 Hopping Charge Transport in Disordered Materials via Localized States 2.3.1 Nearest-neighbor hopping 2.3.2 Variable-range hopping 2.4 Description of Charge-carrier Energy Relaxation and Hopping Conduction in Inorganic Noncrystalline Materials 2.4.1 Dispersive transport in disordered materials 2.4.2 The concept of the transport energy 2.5 Einstein's Relationship for Hopping Electrons 2.5.1 Nonequilibrium charge carriers 2.5.2 Equilibrium charge carriers 2.6 Steady-state Photoconductivity 2.6.1 Low-temperature photoconductivity 2.6.2 Temperature dependence of the photoconductivity 2.7 Thermally Stimulated Currents-a Tool to Determine DOS? 2.8 Dark Conductivity in Amorphous Semiconductors 2.9 Nonlinear Field Effects 2.10 Concluding Remarks References

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Non-Gaussian Transport Measurements and the Einstein Relation in Amorphous Silicon

Cited by 179 publications

References 14 publications

Carrier drift-mobilities and solar cell models for amorphous and nanocrystalline silicon

Carrier drift-mobilities and solar cell models for amorphous and nanocrystalline silicon

Research on High-Bandgap Materials and Amorphous Silicon-Based Solar Cells, Final Technical Report, 15 May 1994-15 January 1998

Description of Charge Transport in Amorphous Semiconductors

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