scholarly journals Manifestations of triplet electronic excitations migration in π-electron containing polymers

2019 ◽  
pp. 242-245
Author(s):  
V. M. Yashchuk ◽  
I. V. Lebedyeva ◽  
O. M. Navozenko
Keyword(s):  
Boundary Conditions ◽  
Excitation Intensity ◽  
Spectral Studies ◽  
Electronic Excitations ◽  
Trip Length ◽  
Deep Traps ◽  
Shallow Traps ◽  
Phosphorescence Spectra ◽  
Triplet Excitons

The results of spectral studies of polymers with aromatic side groups are considered and analyzed. In particular, the phosphorescence spectra of polyvinylcarbazole (PVCa) polyvinyl-7-benzocarbazole (PV7BK) polypropylcarbazole (PEPC) are presented and analyzed. The phosphorescence of these polymers has been shown to be related to the migration of triplet excitons in macromolecules. The phosphorescence of PVC is determined at 77by deep traps (oxides), at 4.2 -shallow traps (monomer units of PVCa). The spreading length of triplet excitons in PVCa macromolecules is 600 A – that corresponds to the average distances between adjacent traps in the macromolecule. There are no such traps in PV7BK macromolecules. The boundary conditions for triplet excitons in macromolecules of PV7BCa were used for evaluation the excitons spreading length. With this aim the dependence of phosphorescence spectra on molecular weihgt were studied The effect of changing of spectral positions of phosphorescence bands when exciton rich the end macromolecular cell was used. The average trip length of triplet excitons is approximately 1000 A. This distance is in fact limited by the probability of the meeting of triplet excitons in the macromolecule and their annihilation at a given excitation intensity.

scholarly journals The Dependencies of X-Ray Conductivity and X-Ray Luminescence of ZnSe Crystals on the Excitation Intensity

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
V. Ya. Degoda ◽  
M. Alizadeh ◽  
N. O. Kovalenko ◽  
N. Yu. Pavlova
Keyword(s):  
Theoretical Analysis ◽  
Single Crystals ◽  
Radiation Intensity ◽  
Excitation Intensity ◽  
Semiconductor Material ◽  
X Ray ◽  
Temperature Range ◽  
Deep Traps ◽  
Shallow Traps

This work studies the conductivity and luminescence of ZnSe single crystals under X-ray irradiation. The experimentally derived lux-ampere characteristics of the X-ray conductivity for ZnSe crystals have a sublinear behavior within the temperature range from 8 to 420 K. The theoretical analysis of the conductivity kinetics at X-ray excitation showed that the value of maximum accumulated lightsum at deep traps does not depend on radiation intensity. However, regarding shallow and phosphorescent traps, the strength of accumulated lightsum depends on the intensity of exciting irradiation. Specifically, these shallow traps and phosphorescent traps cause the sublinear behavior of lux-ampere characteristics in the semiconductor material.

scholarly journals Optische Spektren und Wanderungsmechanismen von Triplettexcitonen in reinen Naphthalinkristallen/Optical Spectra and Transport Mechanism of Triplet Excitons in Pure Naphthalene Crystals

1975 ◽  
Vol 30 (10) ◽  
pp. 1290-1301 ◽  
Author(s):  
H. Port ◽  
H. C. Wolf
Keyword(s):  
Line Width ◽  
Transport Mechanism ◽  
Energy Transfer Mechanism ◽  
Phonon Density ◽  
Characteristic Parameters ◽  
Lorentzian Line ◽  
Increasing Temperature ◽  
Naphthalene Crystal ◽  
Phosphorescence Spectra ◽  
Triplet Excitons

Abstract Phosphorescence spectra of pure naphthalene and perdeutero-naphthalene crystals have been investigated between 4.2 and 300 K. Free-triplet exciton emission can be observed above 40 K only. The temperature dependence of phosphorescence line-width and line-shape has been studied between 60 and 300 K. With increasing temperature the lines are strongly broadened and become asymmetric. Above 150 K they show a red-shift (60 cm-1 at 300 K). The analysis is based on the decomposition of the lines into two components: an unshifted Lorentzian part resulting from coupled coherent and incoherent exciton motion and a sideband contribution built up with the phonon density of states of the naphthalene crystal. The Lorentzian line width is proportional to temperature. The degree of incoherence of exciton motion and characteristic parameters for the energy transfer mechanism are evaluated.

The Effect of Light Soaking on the Photoconductivity Response in A-SI:H

1986 ◽  
Vol 70 ◽  
Author(s):  
Qiu Changhua ◽  
Wu Wenhao ◽  
Zhao Shifu ◽  
Han Daxing
Keyword(s):  
Steady State ◽  
Response Time ◽  
Fermi Level ◽  
Low Temperatures ◽  
Deep Traps ◽  
Temperature Dependences ◽  
The Difference ◽  
Shallow Traps ◽  
Photoconductivity Response ◽  
Effect Of Light

ABSTRACTThe temperature dependences of response time tr and steady state photoconductivity (PC) were used to deduce the DOS at energies above the dark Fermi level. The tr and PC of annealled state A and light soaked state B were measured from 115K to 300K. Light soaking causes degradation of PC. Compared with state A, the PC response of state B is faster at low temperatures, but is slower at high temperatures. The difference between state A and state B was interpreted by a decrease of shallow traps and an increase of deep traps.

scholarly journals Improvement of Dielectric Breakdown Performance by Surface Modification in Polyethylene/TiO2 Nanocomposites

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3346 ◽  
Author(s):  
Weiwang Wang ◽  
Shengtao Li
Keyword(s):  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Interface Region ◽  
Insulation System ◽  
Polar Groups ◽  
Deep Traps ◽  
Relaxation Polarization ◽  
Surface Modified ◽  
Shallow Traps ◽  
Surface Chemical Modification

Dielectric breakdown is a significant property for the insulation system in high voltage power equipment. This paper is dedicated to the improvement of dielectric breakdown by surface-functionalized nanoparticles in low-density polyethylene (LDPE). Prior to the preparation of LDPE/TiO2 nanocomposites, the nanoparticles were surface modified by the silane coupling followed by the chemical reaction process. Results of Fourier transform infrared spectroscopy (FTIR) indicated that some polar groups and chemical bonding were introduced on the surface of TiO2 nanoparticles. A reduction of dielectric permittivity was observed at low nanoparticle loading (<2 wt%) samples, which responded to the restriction of the molecular chain in the interface region. High nanoparticle loadings (2 wt%, 5 wt%, 10 wt%) introduced an obvious relaxation polarization. The trap parameters detected by the thermally stimulated current (TSC) method indicated that the deep traps were introduced by small amounts of nanoparticles (≤2 wt%), while more shallow traps occurred in high loading (5 wt%, 10 wt%) samples. Meanwhile, the increase of breakdown strength at low loading samples were closely related to the deep traps, which was ascribed to the interface region by surface chemical modification.

Luminescence of ZnMoO4 Crystals Developed for the LUMINEU Double Beta Decay Experiment

2015 ◽  
Vol 230 ◽  
pp. 184-192 ◽  
Author(s):  
V.Ya. Degoda ◽  
F.A. Danevich ◽  
N. Coron ◽  
I.M. Ivanov ◽  
Ya.P. Kogut ◽  
...  
Keyword(s):  
Beta Decay ◽  
Emission Spectra ◽  
Double Beta Decay ◽  
Thermally Stimulated Luminescence ◽  
Recombination Luminescence ◽  
Deep Traps ◽  
Scintillation Efficiency ◽  
Shallow Traps ◽  
Double Beta Decay Experiment ◽  
Different Doses

Scintillation efficiency of ZnMoO4 crystals is one of the main characteristics for application in cryogenic double beta decay experiments. Luminescence of ZnMoO4 crystals developed from deeply purified molybdenum under X-ray irradiation of different doses was studied in the temperature interval from 1.4 K to 295 K. Emission spectra, dependence of luminescence intensity on dose and temperature, phosphorescence and thermally stimulated luminescence were investigated. Two emission bands were identified: recombination luminescence at ~ 600 nm and exciton luminescence at ~ 500 nm. We have found that concentration of shallow traps in the material is much greater than the concentration of deep traps. Furthermore only shallow traps absorb a small part of the luminescence and cause the low scintillation efficiency of the sample.

scholarly journals Nonlinear Photocarrier Dynamics and the Role of Shallow Traps in Mixed-Halide Mixed-Cation Hybrid Perovskites

2021 ◽  
Author(s):  
David A. Valverde-Chávez ◽  
Esteban Rojas-Gatjens ◽  
Jacob Williamson ◽  
Sarthak Jariwala ◽  
Yangwei Shi ◽  
...  
Keyword(s):  
Surface Passivation ◽  
Excitation Density ◽  
Shallow Trap ◽  
Time Resolved ◽  
Carrier Trapping ◽  
Carrier Lifetimes ◽  
Deep Traps ◽  
The Impact ◽  
Shallow Traps

<p>We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy. We find that carrier trapping occurs on subnanosecond timescales in both control (unpassivated) and passivated samples, which is consistent within a shallow-trap model. However, the impact of passivation has a direct effect on both shallow and deep traps. Our results reveal that the effect of passivation of deep traps is responsible for the increase of the carrier lifetimes, while the passivation of shallow traps reduces the excitation density required for shallow-trap saturation. Our work demonstrates how ECPL provides details about the passivation of shallow traps beyond those available via conventional time-resolved photoluminescence techniques.</p>

scholarly journals Nonlinear Photocarrier Dynamics and the Role of Shallow Traps in Mixed-Halide Mixed-Cation Hybrid Perovskites

2021 ◽  
Author(s):  
David A. Valverde-Chávez ◽  
Esteban Rojas-Gatjens ◽  
Jacob Williamson ◽  
Sarthak Jariwala ◽  
Yangwei Shi ◽  
...  
Keyword(s):  
Surface Passivation ◽  
Excitation Density ◽  
Shallow Trap ◽  
Time Resolved ◽  
Carrier Trapping ◽  
Carrier Lifetimes ◽  
Deep Traps ◽  
The Impact ◽  
Shallow Traps

<p>We examine the role of surface passivation on carrier trapping and nonlinear recombination dynamics in hybrid metal-halide perovskites by means of excitation correlation photoluminescence (ECPL) spectroscopy. We find that carrier trapping occurs on subnanosecond timescales in both control (unpassivated) and passivated samples, which is consistent within a shallow-trap model. However, the impact of passivation has a direct effect on both shallow and deep traps. Our results reveal that the effect of passivation of deep traps is responsible for the increase of the carrier lifetimes, while the passivation of shallow traps reduces the excitation density required for shallow-trap saturation. Our work demonstrates how ECPL provides details about the passivation of shallow traps beyond those available via conventional time-resolved photoluminescence techniques.</p>

scholarly journals Electron immigration from shallow traps to deep traps by tunnel mechanism on Seydişehir aluminas

2011 ◽  
Vol 131 (12) ◽  
pp. 2625-2629 ◽  
Author(s):  
Erdem Uzun ◽  
Yasemin Yarar ◽  
A. Necmeddin Yazici
Keyword(s):  
Tunnel Mechanism ◽  
Deep Traps ◽  
Shallow Traps

scholarly journals Short-Term Non-Decaying Mechanoluminescence in Li2MgGeO4:Mn2+

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1410
Author(s):  
Yi-Fei Zhu ◽  
Tong Jiang ◽  
Lei Li ◽  
Long-Xiang Cheng ◽  
Jun-Cheng Zhang
Keyword(s):  
Stress Distribution ◽  
Mechanical Stimulation ◽  
Light Sources ◽  
Short Term ◽  
Deep Traps ◽  
Shallow Traps

Trap-controlled mechanoluminescent (ML) materials characterized by reproducible mechanoluminescence (ML) after irradiation recharging have shown attractive prospects in applications including stress distribution visualization, stress-driven light sources, and anti-counterfeiting. However, these materials generally suffer from the difficulty of achieving non-decaying ML when subjected to continuous mechanical stimulation. Herein, we develop a trap-controlled reproducible ML material, Li2MgGeO4:Mn2+, and report its short-term non-decaying ML behavior. Investigation of trap properties suggests that the unique non-decaying ML behavior should arise from the deep traps existing in Li2MgGeO4:Mn2+, which provide electron replenishment for shallow traps that release small numbers of electrons during short-term cyclic friction. Our results are expected to provide a reference for the ultimate achievement of long-term non-decaying ML in such materials.

Research on the Effects of Ultraviolet Aging of Polyethylene Trap Distribution

2014 ◽  
Vol 981 ◽  
pp. 899-902
Author(s):  
Li Juan He ◽  
Chao Zhu ◽  
Huai Chong Huang ◽  
Shan Wang ◽  
Hai Ping Xie ◽  
...  
Keyword(s):  
Electric Field ◽  
Aging Time ◽  
The Body ◽  
Oxidation Products ◽  
Space Charges ◽  
Deep Traps ◽  
Field Distortion ◽  
Before And After ◽  
Shallow Traps ◽  
Ultraviolet Aging

The photo-stimulating discharge (PSD) and ultraviolet-visible spectrometry were used to characterize the polyethylene (PE) and nano-hybrid PE trap before and after ultraviolet aging. In PE with the increasing of ultraviolet aging time, shallow traps reduce gradually and deep traps increase gradually, but for the nano-hybrid PE, shallow traps increase gradually and deep traps reduce gradually. Experiments show that: in the process of aging PE produces oxidation products such as carbonyl, hydroxyl etc. The incorporation of impurities can inhibit the injection of space charges, so as to achieve the purpose of improving electric field distortion in the body of the PE.

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