Spin-Dependent Recombination Effects in a-SI:H Pin Solar Cell Devices: A New Characterization Technique

1995 ◽  
Vol 377 ◽  
Author(s):  
Klaus Lips
Keyword(s):  
Solar Cell ◽  
Defect Density ◽  
Internal Field ◽  
Operating Conditions ◽  
Recombination Rates ◽  
Resonant Enhancement ◽  
Forward Current ◽  
Standard Operating ◽  
Electrically Detected Magnetic Resonance ◽  
Dependent Processes

ABSTRACTElectrically detected magnetic resonance (EDMR) - also often referred to as spin-dependent photoconductivity - is a particularly attractive technique for the investigation of the electronic properties of semiconductor devices. This method detects the paramagnetic states involved in transport and recombination by recording changes of the sample current induced by a resonant enhancement of the recombination rates. This is in contrast to ESR which monitors the resonant enhancement of microwave absorption. Therefore, EDMR is more sensitive by many orders of magnitude than conventional ESR and can be used to investigate a-Si:H solar cell devices under standard operating conditions.In this report we review the EDMR technique and discuss, in detail, the spin-dependent processes controlling dark and photocurrent of standard a-Si:H pin solar cells. In particular, we show that EDMR is sensitive to changes in the internal field of the i layer. We compare the experimental results to numerical calculations of the potential profiles and of EDMR-related quantities. We arrive at the conclusion that degradation by both high forward current and illumination increases the defect density mainly in the i layer, rather than at the pi interface.

Elecrically Detected Magnetic Resonance in A-SI:H Pin Cells

1993 ◽  
Vol 297 ◽  
Author(s):  
Klaus Lips ◽  
Walther Fuhs
Keyword(s):  
Solar Cells ◽  
Magnetic Resonance ◽  
Dark Current ◽  
Defect Density ◽  
Light Exposure ◽  
Forward Bias ◽  
Internal Field ◽  
Exciting Light ◽  
Applied Bias ◽  
Forward Current

We report on a detailed study of EDMR in pin-type solar cells. Like in films the signals are dominated by the contribution of the e-db resonance. It is found that the spectra depend on the applied bias and photon energy of the exciting light. The data suggest that the dark current is controlled by recombination in the bulk of the i-layer. The sign of the signal depends sensitively on the sign of the internal field. At high forward bias and illumination recombination at the pi-interface plays an important role. Degradation by both light exposure and high forward current results predominantly from an increase of the bulk defect density.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

scholarly journals Designs of InGaN Micro-LED Structure for Improving Quantum Efficiency at Low Current Density

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Shiqiang Lu ◽  
Jinchai Li ◽  
Kai Huang ◽  
Guozhen Liu ◽  
Yinghui Zhou ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Current Density ◽  
Carrier Transport ◽  
Defect Density ◽  
Numerical Study ◽  
Structure Design ◽  
Operating Conditions ◽  
Hole Injection ◽  
Electron Blocking Layer ◽  
Recombination Processes

AbstractHere we report a comprehensive numerical study for the operating behavior and physical mechanism of nitride micro-light-emitting-diode (micro-LED) at low current density. Analysis for the polarization effect shows that micro-LED suffers a severer quantum-confined Stark effect at low current density, which poses challenges for improving efficiency and realizing stable full-color emission. Carrier transport and matching are analyzed to determine the best operating conditions and optimize the structure design of micro-LED at low current density. It is shown that less quantum well number in the active region enhances carrier matching and radiative recombination rate, leading to higher quantum efficiency and output power. Effectiveness of the electron blocking layer (EBL) for micro-LED is discussed. By removing the EBL, the electron confinement and hole injection are found to be improved simultaneously, hence the emission of micro-LED is enhanced significantly at low current density. The recombination processes regarding Auger and Shockley–Read–Hall are investigated, and the sensitivity to defect is highlighted for micro-LED at low current density.Synopsis: The polarization-induced QCSE, the carrier transport and matching, and recombination processes of InGaN micro-LEDs operating at low current density are numerically investigated. Based on the understanding of these device behaviors and mechanisms, specifically designed epitaxial structures including two QWs, highly doped or without EBL and p-GaN with high hole concentration for the efficient micro-LED emissive display are proposed. The sensitivity to defect density is also highlighted for micro-LED.

Characterization of the defect density states in MoOx for c-Si solar cell applications

2021 ◽  
pp. 108135
Author(s):  
D. Scirè ◽  
R. Macaluso ◽  
M. Mosca ◽  
S. Mirabella ◽  
A. Gulino ◽  
...  
Keyword(s):  
Solar Cell ◽  
Defect Density ◽  
Si Solar Cell

Comparison of Current and Light Induced Defects in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A. Street ◽  
W.B. Jackson ◽  
M. Hack
Keyword(s):  
Numerical Modelling ◽  
Reverse Bias ◽  
Defect Density ◽  
Reverse Current ◽  
Bias Current ◽  
Spatial Profile ◽  
Forward Current ◽  
Defect Creation ◽  
Induced Defects ◽  
Metastable Defect

Metastable defect creation by illumination and by a forward current in p-i-n devices are compared using CPM and reverse current measurements of the defect density. The data show that the same defects are formed by the two mechanisms, but with different spatial profiles. Numerical modelling shows how the spatial profile influences the reverse bias current.

Studies of Degradation in Nichia AlGaN/InGaN/GaN Blue Light Emitting Diodes Under Close to Normal Operating Conditions

1996 ◽  
Vol 421 ◽  
Author(s):  
M. Osiński ◽  
D. L. Barton ◽  
C. J. Helms ◽  
P. Perlin ◽  
N. H. Berg ◽  
...  
Keyword(s):  
Blue Light ◽  
Light Emitting Diodes ◽  
Defect Density ◽  
Degradation Process ◽  
Operating Conditions ◽  
Similar Amount ◽  
Life Testing ◽  
Light Emitting ◽  
High Pulsed Current ◽  
The Impact

AbstractThe reliability of devices fabricated in GaN and related alloys, especially under high current densities as would be found in lasers, has yet to be fully characterized. Our previous work [1] investigated the degradation of GaN-based blue light emitting diodes (LEDs) under high pulsed current stress. This work indicated a possible correlation between the high crystal defect density and failures caused by metal migration along these defect tubes. To assess the impact of this data on devices under more normal conditions, several LEDs from both older and more recent production lots were placed in a controlled temperature and current environment for several thousand hours. The test started with a constant 20 mA current for the first 1000 hours and continued for another 1650 hours at various currents up to 70 mA, all at a temperature of 23 °C. During this test, one of the older generation LED's output degraded by more than 50%. Subsequent failure analysis showed that this was caused by a crack which isolated part of the active region from the p-contact. The remaining LEDs were returned to life testing where the temperature was subsequently increased by 5 °C after each 500 hours of testing. The output from one of the newer LEDs dreiven at 70 mA degraded to 55% of its original value after 3600 hours and a second newer LED degraded by a similar amount after 4400 hours. The first failure, LED #16, did not exhibit a significant change in its I-V characteristics indicating that a change in the package transparency was a likely cause for the observed degradation. The second failure, LED #17, did show a noticeable change in its I-V characteristics. This device was subsequently returned to life testing where the degradation process will be monitored for further changes.

Annealing Kinetics of Amorphous Silicon Alloy Solar Cells Made at Various Deposition Rates

2001 ◽  
Vol 664 ◽  
Author(s):  
Baojie Yana ◽  
Jeffrey Yanga ◽  
Kenneth Lord ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
High Frequency ◽  
Room Temperature ◽  
Defect Density ◽  
Very High Frequency ◽  
Solar Cell Performance ◽  
Kinetics Of ◽  
Very High

ABSTRACTA systematic study has been made of the annealing kinetics of amorphous silicon (a-Si) alloy solar cells. The cells were deposited at various rates using H2 dilution with radio frequency (RF) and modified very high frequency (MVHF) glow discharge. In order to minimize the effect of annealing during light soaking, the solar cells were degraded under 30 suns at room temperature to quickly reach their saturated states. The samples were then annealed at an elevated temperature. The J-V characteristics were recorded as a function of annealing time. The correlation of solar cell performance and defect density in the intrinsic layer was obtained by computer simulation. Finally, the annealing activation energy distribution (Ea) was deduced by fitting the experimental data to a theoretical model. The results show that the RF low rate solar cell with high H2 dilution has the lowest Ea and the narrowest distribution, while the RF cell with no H2 dilution has the highest Ea and the broadest distribution. The MVHF cell made at 8Å/s withhigh H2 dilution shows a lower Ea and a narrower distribution than the RF cell made at 3 Å/s, despite the higher rate. We conclude that different annealing kinetics plays an important role in determining the stabilized performance of a-Si alloy solar cells.

Hydrogenated Amorphous Silicon Germanium Alloy for Stable Solar Cells

1994 ◽  
Vol 336 ◽  
Author(s):  
A. Terakawa ◽  
M. Shima ◽  
K. Sayama ◽  
H. Tarui ◽  
H. Nishiwaki ◽  
...  
Keyword(s):  
Solar Cell ◽  
Conversion Efficiency ◽  
Silicon Germanium ◽  
Defect Density ◽  
Characteristic Energy ◽  
Solar Cell Performance ◽  
Germanium Content ◽  
Junction Solar Cell ◽  
Degradation Ratio ◽  
Double Junction

ABSTRACTThe film properties and solar cell performance of a-SiGe:H samples with the same optical gap and different combinations of hydrogen content (CH) and germanium content (CGe) have been compared. The optimum composition for the initial properties, such as the tail characteristic energy, defect density and conversion efficiency of the solar cell, was determined, and the differences could be explained by the difference in H bonding configuration. The degradation ratio of the conversion efficiency becomes larger in higher CH samples. This suggests that hydrogen or Si-H2 participates in light-induced degradation. As a result, the optimum CH for an efficient solar cell is believed to shift to the lower CH region after light soaking. Based on these findings, the stabilized conversion efficiency of 3.3% under red light (γ>650nm) for an a-SiGe:H single-junction solar cell (1cm2) and 10.6% under lsun light for an a-Si/a-SiGe double-junction stacked solar cell (1cm2) have been achieved. The degradation ratio is only 8.6% for the double-junction solar cell.

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