scholarly journals Tunable Luminescent A-SiNxOy Films with High Internal Quantum Efficiency and Fast Radiative Recombination Rates

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2494
Author(s):  
Pengzhan Zhang ◽  
Leng Zhang ◽  
Xuefeng Ge ◽  
Sake Wang
Keyword(s):  
Radiative Recombination ◽  
Light Emission ◽  
Internal Quantum Efficiency ◽  
Silicon Oxynitride ◽  
Quantum Yields ◽  
Planar Geometry ◽  
Defect States ◽  
Recombination Rates ◽  
Time Resolved ◽  
Level Model

In this work, we systematically investigated the Nx bonding defects that induced high photoluminescence internal quantum efficiencies (PL IQEs) and very fast radiative recombination processes in amorphous silicon oxynitride (a-SiNxOy) systems. The luminescent N‒Si‒O bonding-related defect states were checked for the XPS, EPR, and temperature-dependent steady-state PL (TD-SSPL) properties. The PL IQEs were calculated from PL quantum yields through the principle of planar geometry optics, and then confirmed by the TD-SSPL properties. The radiative recombination rates [kr(R)] were determined by combining the PL IQE values and ns-PL lifetimes obtained from time-resolved PL measurements. Both the PL IQE, exceeding 72%, and the fast kr(R) (~108 s−1) are proportional to the concentration of Nx defects, which can be explained by N‒Si‒O bonding states related to the quasi-three-level model, suggesting the possible realization of stimulated light emission in a-SiNxOy systems.

scholarly journals Purely Organic Phosphor Sensitization Based Highly Efficient Electrofluorescence Material

2021 ◽  
Author(s):  
Jiaxuan Wang ◽  
Baoyan Liang ◽  
Jinbei Wei ◽  
Yincai Xu ◽  
Zhiqiang Li ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Light Emission ◽  
Internal Quantum Efficiency ◽  
Energy Levels ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Carrier Injection ◽  
Light Emitting Devices ◽  
Highly Efficient ◽  
New Strategy

Pure organic room temperature phosphorescence (RTP) materials are considered as potential candidates for replacing precious metal-based complexes to fabricate highly efficient organic light emitting devices (OLEDs). However, for reported RTP materials, low photoluminescence quantum yields (PLQYs) in thin film state seriously impede their applications in OLEDs. On the other hand, how using normal organic fluorescence materials to fabricate OLEDs with an internal quantum efficiency (IQE) over 25% remains a great unaddressed issue beyond the thermally activated delayed fluorescence (TADF) sensitization approach. Here, we establish a strategy to construct highly efficient OLEDs based on pure organic RTP material sensitized fluorescence emitter. The key point for our strategy is that benzimidazole-triazine molecules (PIM-TRZ), 2,6-di(phenothiazinyl)naphthalene (β-DPTZN) and 5,6,11,12-tetraphenylnaphthacene (rubrene) were screened as host, phosphor sensitizer and fluorescent emitter, respectively. Detail photophysical characterizations demonstrate that the host material PIMTRZ with unique RTP nature is critical for achieving phosphor sensitizing process. As an organic RTP compound, the singlet and triplet state energy levels of β-DPTZN perfectly match with those of PIMTRZ, resulting in the formation and lasting existence of phosphor’s excitons in emitting layer. The large overlap between the absorption spectrum of rubrene and PL spectrum of PIM-TRZ:10% β-DPTZN film can facilitate the Förster energy transfer from the triplet β-DPTZN to the singlet rubrene and the finally displayed fluorescence is derived from singlet excited states of rubrene. The perfect collocation of host, phosphorescent sensitizer and fluorescent emitter in the emitting layer promise the predominant performance of the devices with external quantum efficiency (EQE) of 15.7%. The PLQY of emitting layer is 60.3%, and therefore about 90% carrier injection induced excitons are harvested for light emission. We present a new strategy to fabricate efficient fluorescent devices by employing ingenious combination of host, phosphorescent sensitizer and fluorescent emitter, which is significant to the development of OLEDs.<br>

scholarly journals Purely Organic Phosphor Sensitization Based Highly Efficient Electrofluorescence Material

2021 ◽  
Author(s):  
Jiaxuan Wang ◽  
Baoyan Liang ◽  
Jinbei Wei ◽  
Yincai Xu ◽  
Zhiqiang Li ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Light Emission ◽  
Internal Quantum Efficiency ◽  
Energy Levels ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Carrier Injection ◽  
Light Emitting Devices ◽  
Highly Efficient ◽  
New Strategy

Pure organic room temperature phosphorescence (RTP) materials are considered as potential candidates for replacing precious metal-based complexes to fabricate highly efficient organic light emitting devices (OLEDs). However, for reported RTP materials, low photoluminescence quantum yields (PLQYs) in thin film state seriously impede their applications in OLEDs. On the other hand, how using normal organic fluorescence materials to fabricate OLEDs with an internal quantum efficiency (IQE) over 25% remains a great unaddressed issue beyond the thermally activated delayed fluorescence (TADF) sensitization approach. Here, we establish a strategy to construct highly efficient OLEDs based on pure organic RTP material sensitized fluorescence emitter. The key point for our strategy is that benzimidazole-triazine molecules (PIM-TRZ), 2,6-di(phenothiazinyl)naphthalene (β-DPTZN) and 5,6,11,12-tetraphenylnaphthacene (rubrene) were screened as host, phosphor sensitizer and fluorescent emitter, respectively. Detail photophysical characterizations demonstrate that the host material PIMTRZ with unique RTP nature is critical for achieving phosphor sensitizing process. As an organic RTP compound, the singlet and triplet state energy levels of β-DPTZN perfectly match with those of PIMTRZ, resulting in the formation and lasting existence of phosphor’s excitons in emitting layer. The large overlap between the absorption spectrum of rubrene and PL spectrum of PIM-TRZ:10% β-DPTZN film can facilitate the Förster energy transfer from the triplet β-DPTZN to the singlet rubrene and the finally displayed fluorescence is derived from singlet excited states of rubrene. The perfect collocation of host, phosphorescent sensitizer and fluorescent emitter in the emitting layer promise the predominant performance of the devices with external quantum efficiency (EQE) of 15.7%. The PLQY of emitting layer is 60.3%, and therefore about 90% carrier injection induced excitons are harvested for light emission. We present a new strategy to fabricate efficient fluorescent devices by employing ingenious combination of host, phosphorescent sensitizer and fluorescent emitter, which is significant to the development of OLEDs.<br>

Enhancement of the Fluorescence Quantum Yield of Thiol-Stabilized CdTe Quantum Dots Through Surface Passivation with Sodium Chloride and Bicarbonate

2018 ◽  
Vol 232 (9-11) ◽  
pp. 1399-1412 ◽  
Author(s):  
Tetiana Dudka ◽  
Stephen V. Kershaw ◽  
Shumin Lin ◽  
Julian Schneider ◽  
Andrey L. Rogach
Keyword(s):  
Quantum Dots ◽  
Quantum Yield ◽  
Radiative Recombination ◽  
Surface Passivation ◽  
Surface Defects ◽  
Fold Increase ◽  
Light Sources ◽  
Recombination Rates ◽  
Time Resolved ◽  
Cdte Qds

Abstract Colloidal quantum dots (QDs) have potential for several applications, e.g. as novel light sources; as photoluminescent probes; and for solar energy conversion devices, but their sensitivity towards their environmental surroundings, and the presence of surface defects may still degrade their emission properties. Herein, we present a post-synthetic treatment of CdTe QDs stabilized by mixed thiol ligands using chloride and bicarbonate ions to achieve near-complete surface passivation, resulting in a two-fold increase of the photoluminescence quantum yield (PL QY) and significant suppression of non-radiative recombination. Time-resolved PL measurements reveal fluorescence lifetime and PL QY trends did not both track identically; in the most favorable cases a suppression of non-radiative recombination and a slight increase in the radiative recombination rates after the salt treatment took place. The optimized conditions demonstrated here are proven to work for different sizes of CdTe QDs, and also show a dependence on the composition of the mixed ligand systems used.

scholarly journals Carrier excitation dynamics in black silicon nano pillar arrays

2020 ◽  
Author(s):  
SEREF KALEM
Keyword(s):  
Time Constant ◽  
Radiative Recombination ◽  
Surface Defects ◽  
Light Emission ◽  
Slow Component ◽  
Green Emission ◽  
Recombination Process ◽  
Black Silicon ◽  
Defect States ◽  
Pillar Arrays

Abstract Black silicon has attracted a great deal of interest for its promising photonic applications and exciting physical properties. Several approaches have been used to demonstrate the possibility of producing black silicon with CW light emission, but the investigation of a detailed radiative dynamical properties of the recombination process is still lacking. Here, we present ultrafast radiative recombination phenomena from black silicon consisting of quantum pillars produced by plasma ion etching. An ultrafast blue luminescence component competing with non-radiative recombination at surface defects was identified as no-phonon recombination process. This component involves two decay processes with a peak energy at around 480 nm, which have the fast component of about 10 ps followed by a component of around 50 ps decay time constant. The emission exhibits slow component in red spectral region with time constant ranging from 1.5 to 2.5 ns. When the surface of nano pillars is smoothed, the slow component at around 600 nm is enhanced to the detriment of blue-green emission, increasing the lifetime of carriers within the Si core of the quantum pillars. This process results in a slower sates assuming a 3-component exponential decay as measured by Streak camera. The ultrafast PL decay leads to a transfer of carriers to long-lived defect states as evidenced by a red emission at around 2 eV. The results are interpreted through the presence of quantum confinement at the tip regions of the pillars and surface defects originating from the oxide environment surrounding the nanometer size pillars.

Exciton dynamics in thick GaN MOVPE epilayers deposited on sapphire.

1997 ◽  
Vol 2 ◽  
Author(s):  
J. Allègre ◽  
P. Lefebvre ◽  
J. Camassel ◽  
B. Beaumont ◽  
Pierre Gibart
Keyword(s):  
Layer Thickness ◽  
Buffer Layers ◽  
Rate Equations ◽  
Time Resolved ◽  
Versus Layer ◽  
Level Model ◽  
Shallow Impurities ◽  
Aln Buffer ◽  
Time Resolved Photoluminescence

Time-resolved photoluminescence spectra have been recorded on three GaN epitaxial layers of thickness 2.5 μm, 7 μm and 16 μm, at various temperatures ranging from 8K to 300K. The layers were deposited by MOVPE on (0001) sapphire substrates with standard AlN buffer layers. To achieve good homogeneities, the growth was in-situ monitored by laser reflectometry. All GaN layers showed sharp excitonic peaks in cw PL and three excitonic contributions were seen by reflectivity. The recombination dynamics of excitons depends strongly upon the layer thickness. For the thinnest layer, exponential decays with τ ~ 35 ps have been measured for both XA and XB free excitons. For the thickest layer, the decay becomes biexponential with τ1 ~ 80 ps and τ2 ~ 250 ps. These values are preserved up to room temperature. By solving coupled rate equations in a four-level model, this evolution is interpreted in terms of the reduction of density of both shallow impurities and deep traps, versus layer thickness, roughly following a L−1 law.

Analysis of 0.13 μm CMOS Technology Using Time Resolved Light Emission

2004 ◽  
Author(s):  
Peter Ouimet ◽  
Jason Goertz ◽  
Olivier Rinaudo ◽  
Lousinda Long ◽  
Simon Yeung
Keyword(s):  
Light Emission ◽  
Cmos Technology ◽  
Case Histories ◽  
Time Resolved ◽  
Scan Chain

Abstract This paper describes case histories of 0.13 um bulk CMOS technology analyses using Time Resolved Light Emission (TRLEM). Using this technique, scan chain, timing, and logic failures are shown to be quickly and decisively identified thereby meeting the need for rapid feedback on 1st silicon failures and process excursions.

scholarly journals Perspectives on UVC LED: Its Progress and Application

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 196
Author(s):  
Tsung-Chi Hsu ◽  
Yu-Tsai Teng ◽  
Yen-Wei Yeh ◽  
Xiaotong Fan ◽  
Kuo-Hsiung Chu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Flip Chip ◽  
Layer Structure ◽  
Light Emitting Diode ◽  
Internal Quantum Efficiency ◽  
Reverse Current ◽  
Light Extraction ◽  
Epitaxial Layers ◽  
High Electron ◽  
Recombination Rates

High-quality epitaxial layers are directly related to internal quantum efficiency. The methods used to design such epitaxial layers are reviewed in this article. The ultraviolet C (UVC) light-emitting diode (LED) epitaxial layer structure exhibits electron leakage; therefore, many research groups have proposed the design of blocking layers and carrier transportation to generate high electron–hole recombination rates. This also aids in increasing the internal quantum efficiency. The cap layer, p-GaN, exhibits high absorption in deep UV radiation; thus, a small thickness is usually chosen. Flip chip design is more popular for such devices in the UV band, and the main factors for consideration are light extraction and heat transportation. However, the choice of encapsulation materials is important, because unsuitable encapsulation materials will be degraded by ultraviolet light irradiation. A suitable package design can account for light extraction and heat transportation. Finally, an atomic layer deposition Al2O3 film has been proposed as a mesa passivation layer. It can provide a low reverse current leakage. Moreover, it can help increase the quantum efficiency, enhance the moisture resistance, and improve reliability. UVC LED applications can be used in sterilization, water purification, air purification, and medical and military fields.

Quantum Light Emission from Coupled Defect States in DNA-Functionalized Carbon Nanotubes

ACS Nano ◽  
2021 ◽  
Author(s):  
Yu Zheng ◽  
Younghee Kim ◽  
Andrew C. Jones ◽  
Gabrielle Olinger ◽  
Eric R. Bittner ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Light Emission ◽  
Defect States ◽  
Functionalized Carbon Nanotubes

Photodissociation of ClONO2:  2. Time-Resolved Absorption Studies of Product Quantum Yields

1997 ◽  
Vol 101 (36) ◽  
pp. 6667-6678 ◽  
Author(s):  
R. J. Yokelson ◽  
James B. Burkholder ◽  
R. W. Fox ◽  
A. R. Ravishankara
Keyword(s):  
Quantum Yields ◽  
Time Resolved ◽  
Absorption Studies

Direct measurement of the recombination rates in bulk InSb by time‐resolved photoluminescence

1992 ◽  
Vol 71 (10) ◽  
pp. 5140-5145 ◽  
Author(s):  
Robert D. Grober ◽  
H. Dennis Drew ◽  
Geoffrey L. Burdge ◽  
Brian S. Bennett
Keyword(s):  
Direct Measurement ◽  
Recombination Rates ◽  
Time Resolved ◽  
Time Resolved Photoluminescence
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