Midgap Defects in a-SiGe:H Devices from Capacitance Measurements

1989 ◽  
Vol 149 ◽  
Author(s):  
Steven S. Hegedus ◽  
Theodore X. Zhou
Keyword(s):  
Solar Cells ◽  
Fermi Level ◽  
Density Of States ◽  
Capacitance Measurements

ABSTRACTWe have measured the capacitance of a-SiGe:H p-i-n solar cells as functions of temperature, frequency and bias. The density of states at the Fermi level g(EF) has been determined from two methods. We find that g(EF) increases from 1–2×1016 to 5–10×1017/(cm3eV) as the Ge content increases from 0 to 63%.

Polymorphous Silicon: Transport Properties and Solar Cell Applications

1999 ◽  
Vol 557 ◽  
Author(s):  
C. Longeaud ◽  
J. P. Kleider ◽  
M. Gauthier ◽  
R. Brtiggemann ◽  
Y. Poissant ◽  
...  
Keyword(s):  
Fermi Level ◽  
Transport Properties ◽  
Density Of States ◽  
Diffusion Length ◽  
Hydrogenated Amorphous Silicon ◽  
Capacitance Measurements ◽  
New Material ◽  
Hydrogenated Amorphous ◽  
Minority Carriers ◽  
Excellent Stability

AbstractTransport properties of hydrogenated polymorphous silicon layers (pm-Si:H) deposited at 150°C under various pressures in the range 80-293 Pa in sandwich (Schottky and p-i-n diodes) and coplanar structures have been compared to those of hydrogenated amorphous silicon (a-Si:H) samples deposited at the same temperature in standard conditions. The layers have been studied as-deposited, annealed and after light-soaking. With increasing pressure up to 240 Pa: i) the density of states above the Fermi level decreases as determined by means of the modulated photocurrent technique, ii) the mobility-lifetime products of electrons and holes measured by means of steady-state photoconductivity and photocarrier grating techniques both increase. The highest values for the diffusion length of minority carriers exceed 200 nm. Capacitance measurements as a function of frequency and temperature show that the density of states at the Fermi level is lower in the pm-Si:H than in the a-Si:H films. After light-soaking the diffusion length of minority carriers in a-Si:H is reduced by a factor oftwo whereas it is less reduced or not affected in the pm-Si:H layers. Solar cells including this new material present an excellent stability.

scholarly journals Investigation of single-domain Au silicide nanowires on Si(110) formed for Au coverages in the monolayer regime

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stephan Appelfeller
Keyword(s):  
Fermi Level ◽  
Surface Structure ◽  
Density Of States ◽  
The Self ◽  
Single Domain ◽  
Photoemission Spectroscopy ◽  
Annealing Temperatures ◽  
Self Organized ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy

AbstractThe self-organized formation of single domain Au silicide nanowires is observed on Si(110). These nanowires are analysed using scanning tunnelling microscopy (STM) and spectroscopy (STS) as well as photoemission spectroscopy (PES). Core-level PES is utilised to confirm the formation of Au silicide and establish its presence as the top most surface structure, i.e., the nanowires. The growth of the Au silicide nanowires and their dimensions are studied by STM. They form for Au coverages of about 1 monolayer and are characterized by widths of about 2 to 3 nm and heights below 1 nm while reaching lengths exceeding 500 nm when choosing appropriate annealing temperatures. Valence band PES and STS indicate a small but finite density of states at the Fermi level typical for compound metals.

scholarly journals On the Relation between the Open‐Circuit Voltage and Quasi‐Fermi Level Splitting in Efficient Perovskite Solar Cells

2019 ◽  
Vol 9 (33) ◽  
pp. 1901631 ◽  
Author(s):  
Pietro Caprioglio ◽  
Martin Stolterfoht ◽  
Christian M. Wolff ◽  
Thomas Unold ◽  
Bernd Rech ◽  
...  
Keyword(s):  
Solar Cells ◽  
Fermi Level ◽  
Open Circuit Voltage ◽  
Perovskite Solar Cells ◽  
Open Circuit ◽  
Quasi Fermi Level ◽  
Level Splitting

scholarly journals Ion Movement Explains Huge V OC Increase despite Almost Unchanged Internal Quasi‐Fermi‐Level Splitting in Planar Perovskite Solar Cells

2021 ◽  
pp. 2001104
Author(s):  
Jan Herterich ◽  
Moritz Unmüssig ◽  
Georgios Loukeris ◽  
Markus Kohlstädt ◽  
Uli Würfel
Keyword(s):  
Solar Cells ◽  
Fermi Level ◽  
Perovskite Solar Cells ◽  
Ion Movement ◽  
Quasi Fermi Level ◽  
Level Splitting

Photosensitive tunneling in superconductivity

1970 ◽  
Vol 48 (5) ◽  
pp. 630-631 ◽  
Author(s):  
V. Radhakrishnan
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Tunneling Current ◽  
Theoretical Treatment ◽  
Photoconductive Property

Theoretical treatment of the model proposed by Giaever for his experiment on the photosensitive tunneling in superconductors is examined. New relations are derived which connect the photoconductive property of the barrier and the tunneling current. These relations are helpful to check the model and to determine the density of states for the trapped holes at the hole Fermi level.

scholarly journals An ab-initio study on structural, elastic, electronic, bonding, thermal, and optical properties of topological Weyl semimetal TaX (X = P, As)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. I. Naher ◽  
S. H. Naqib
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Electronic Band Structure ◽  
Optical Parameters ◽  
Electronic Density ◽  
Electronic Band ◽  
Wide Range ◽  
Weyl Semimetals

AbstractIn recent days, study of topological Weyl semimetals have become an active branch of physics and materials science because they led to realization of the Weyl fermions and exhibited protected Fermi arc surface states. Therefore, topological Weyl semimetals TaX (X = P, As) are important electronic systems to investigate both from the point of view of fundamental physics and potential applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with quasi-linear energy dispersions in certain sections of the Brillouin zone near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As).The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations.

Uphill and downhill charge generation from charge transfer to charge separated states in organic solar cells

2021 ◽  
Author(s):  
Shahidul Alam ◽  
Vojtech Nádaždy ◽  
Tomáš Váry ◽  
Christian Friebe ◽  
Rico Meitzner ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Solar Cells ◽  
Charge Transfer ◽  
Energy Level ◽  
Density Of States ◽  
Organic Solar Cells ◽  
Joint Density ◽  
Charge Generation ◽  
Donor Acceptor

Energy level alignments at the organic donor–acceptor interface cannot be predicted from cyclic voltammetry. Onsets for joint density of states and charge generation, reveal cases of energy uphill and – newly observed – downhill charge generation.

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