Efficient perovskite light-emitting diodes by film annealing temperature control

RSC Advances ◽  
2016 ◽  
Vol 6 (75) ◽  
pp. 71070-71075 ◽  
Author(s):  
Junqing Liang ◽  
Yongqiang Zhang ◽  
Xiaoyang Guo ◽  
Zhihong Gan ◽  
Jie Lin ◽  
...  
Keyword(s):  
Temperature Control ◽  
Annealing Temperature ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
Film Annealing

A bright perovskite light-emitting diode has been fabricated through film annealing temperature control.

scholarly journals Unravelling the electron injection/transport mechanism in organic light-emitting diodes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tsubasa Sasaki ◽  
Munehiro Hasegawa ◽  
Kaito Inagaki ◽  
Hirokazu Ito ◽  
Kazuma Suzuki ◽  
...  
Keyword(s):  
Work Function ◽  
Transport Mechanism ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Electron Injection ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light ◽  
Materials Used

AbstractAlthough significant progress has been made in the development of light-emitting materials for organic light-emitting diodes along with the elucidation of emission mechanisms, the electron injection/transport mechanism remains unclear, and the materials used for electron injection/transport have been basically unchanged for more than 20 years. Here, we unravelled the electron injection/transport mechanism by tuning the work function near the cathode to about 2.0 eV using a superbase. This extremely low-work function cathode allows direct electron injection into various materials, and it was found that organic materials can transport electrons independently of their molecular structure. On the basis of these findings, we have realised a simply structured blue organic light-emitting diode with an operational lifetime of more than 1,000,000 hours. Unravelling the electron injection/transport mechanism, as reported in this paper, not only greatly increases the choice of materials to be used for devices, but also allows simple device structures.

Electrically driven single microribbon based near-infrared exciton-polariton light-emitting diode

CrystEngComm ◽  
2021 ◽  
Author(s):  
Mingming Jiang ◽  
Fupeng Zhang ◽  
Kai Tang ◽  
Peng Wan ◽  
Caixia Kan
Keyword(s):  
High Performance ◽  
Near Infrared ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Light Sources ◽  
Coherent Light ◽  
Light Emitting ◽  
Exciton Polaritons ◽  
Laser Devices

Achieving electrically-driven exciton-polaritons has drawn substantial attention toward developing ultralow-threshold coherent light sources, containing polariton laser devices and high-performance light-emitting diodes (LEDs). In this work, we demonstrate an electrically driven...

scholarly journals The Optical Properties of InGaN/GaN Nanorods Fabricated on (-201) β-Ga2O3 Substrate for Vertical Light Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 42
Author(s):  
Jie Zhao ◽  
Weijiang Li ◽  
Lulu Wang ◽  
Xuecheng Wei ◽  
Junxi Wang ◽  
...  
Keyword(s):  
Stark Effect ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Strain Relaxation ◽  
Blue Shift ◽  
Peak Position ◽  
Excitation Power ◽  
Light Extraction Efficiency ◽  
Excitation Power Density ◽  
Light Emitting

We fabricated InGaN/GaN nanorod light emitting diode (LED) on (-201) β-Ga2O3 substrate via the SiO2 nanosphere lithography and dry-etching techniques. The InGaN/GaN nanorod LED grown on β-Ga2O3 can effectively suppress quantum confined Stark effect (QCSE) compared to planar LED on account of the strain relaxation. With the enhancement of excitation power density, the photoluminescence (PL) peak shows a large blue-shift for the planar LED, while for the nanorod LED, the peak position shift is small. Furthermore, the simulations also show that the light extraction efficiency (LEE) of the nanorod LED is approximately seven times as high as that of the planar LED. Obviously, the InGaN/GaN/β-Ga2O3 nanorod LED is conducive to improving the optical performance relative to planar LED, and the present work may lay the groundwork for future development of the GaN-based vertical light emitting diodes (VLEDs) on β-Ga2O3 substrate.

All-solution processed inverted green quantum dot light-emitting diodes with concurrent high efficiency and long lifetime

2019 ◽  
Vol 6 (10) ◽  
pp. 2009-2015 ◽  
Author(s):  
Zhiwen Yang ◽  
Qianqian Wu ◽  
Gongli Lin ◽  
Xiaochuan Zhou ◽  
Weijie Wu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Shell Growth ◽  
Solution Processed ◽  
Light Emitting ◽  
Long Lifetime

An all-solution processed inverted green quantum dot-based light-emitting diode with concurrent high efficiency and long lifetime is obtained by precisely controlled double shell growth of quantum dots.

Light-emitting diodes as light sources for spectroscopy: Sensitivity to temperature

2017 ◽  
Vol 25 (6) ◽  
pp. 416-422 ◽  
Author(s):  
Clinton J Hayes ◽  
Kerry B Walsh ◽  
Colin V Greensill
Keyword(s):  
Ambient Temperature ◽  
Near Infrared ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Junction Temperature ◽  
Effect Of Temperature ◽  
Light Sources ◽  
Spectral Variation ◽  
Light Emitting ◽  
Full Intensity

Understanding of light-emitting diode lamp behaviour is essential to support the use of these devices as illumination sources in near infrared spectroscopy. Spectral variation in light-emitting diode peak output (680, 700, 720, 735, 760, 780, 850, 880 and 940 nm) was assessed over time from power up and with variation in environmental temperature. Initial light-emitting diode power up to full intensity occurred within a measurement cycle (12 ms), then intensity decreased exponentially over approximately 6 min, a result ascribed to an increase in junction temperature as current is passed through the light-emitting diode. Some light-emitting diodes displayed start-up output characteristics on their first use, indicating the need for a short light-emitting diode ‘burn in’ period, which was less than 24 h in all cases. Increasing the ambient temperature produced a logarithmic decrease in overall intensity of the light-emitting diodes and a linear shift to longer wavelength of the peak emission. This behaviour is consistent with the observed decrease in the IAD Index (absorbance difference between 670 nm and 720 nm, A670–A720) with increased ambient temperature, as measured by an instrument utilising light-emitting diode illumination (DA Meter). Instruments using light-emitting diodes should be designed to avoid or accommodate the effect of temperature. If accommodating temperature, as light-emitting diode manufacturer specifications are broad, characterisation is recommended.

Experimental investigation and empirical modelling of thermal and drive current effect on optical performance of commercial LEDs

2020 ◽  
pp. 147715352097693
Author(s):  
AN Padmasali ◽  
SG Kini
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Operating Conditions ◽  
Junction Temperature ◽  
Optimum Operating ◽  
Current Effect ◽  
Drive Current ◽  
Light Emitting ◽  
Empirical Modelling ◽  
Output Performance

Light-emitting diode is the most dominant lighting technology, and lumen output performance is dependent on junction temperature and operating drive current. An experimental analysis is performed to study the thermal and drive current effect on lumen output, and an empirical model is developed to determine the optimum operating conditions of temperature and drive current so as to obtain a maximum lumen output profile. Three commercially available light-emitting diode down-lighter’s light-emitting diodes are chosen for the study. The investigation reveals that there exists an optimum drive current at which lumen output is maximum, and it has a linear relation with junction temperature. Pulse-soak testing was performed to study the deviations of pulsed and continuous operation of drive current to understand the performance of light-emitting diodes. The work helps light-emitting diode luminaire manufacturers to design a controlled power electronic circuit so as to maximize the lumen output effectively and accurately.

High efficiency above 20% in polymeric thermally activated delayed fluorescent organic light-emitting diodes by a host embedded backbone structure

2019 ◽  
Vol 10 (35) ◽  
pp. 4872-4878 ◽  
Author(s):  
Yun Hwan Park ◽  
Ho Jin Jang ◽  
Jun Yeob Lee
Keyword(s):  
High Efficiency ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Thermally Activated ◽  
Highly Efficient ◽  
Organic Light ◽  
Backbone Structure

A highly efficient polymeric thermally activated delayed fluorescent (TADF) organic light-emitting diode was developed by synthesizing a copolymer with 9-vinylcarbazole (VCz) and TADF repeating units.

Colour-enhanced light emitting diode light with high gamut area for retail lighting

2015 ◽  
Vol 49 (3) ◽  
pp. 329-342 ◽  
Author(s):  
XF Feng ◽  
W Xu ◽  
QY Han ◽  
SD Zhang
Keyword(s):  
Light Source ◽  
Light Emitting Diodes ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Broad Band ◽  
Area Index ◽  
Light Emitting ◽  
High Preference ◽  
Colour Rendering ◽  
Colour Appearance

Light emitting diodes with high colour quality were investigated to enhance colour appearance and improve observers' preference for the illuminated objects. The spectral power distributions of the light emitting diodes were optimised by changing the ratios of the narrow band red, green and blue light emitting diodes, and the phosphor-converted broad-band light emitting diode to get the desired colour rendering index and high gamut area index. The influence of the light emitting diode light on different coloured fabrics was investigated. The experimental results and the statistical analysis show that by optimising the red, green, blue components the light emitting diode light can affect the colour appearance of the illuminated fabrics positively and make the fabrics appear more vivid and saturated due to the high gamut area index. Observers indicate a high preference for the colours whose saturations are enhanced. The results reveal that the colour-enhanced light emitting diode light source can better highlight products and improve visual impression over the ceramic metal halide lamp and the phosphor-converted light emitting diode light source.

Temperature Regulation for LED Lamps Using Fans

2013 ◽  
Vol 753-755 ◽  
pp. 1931-1938
Author(s):  
Hyeung Sik Choi ◽  
Hee Young Shin ◽  
Ji Youn Oh ◽  
Tae Woo Lim ◽  
Yun Hae Kim
Keyword(s):  
Temperature Control ◽  
Temperature Regulation ◽  
Light Emitting Diode ◽  
Operation Time ◽  
Heat Sinks ◽  
Optimal Size ◽  
Light Emitting ◽  
Regulation Scheme ◽  
Cooling Fan ◽  
Relationship Of

A temperature regulation control for LED(Light Emitting Diode) lamp using a cooling fan was studied. An efficient temperature regulation scheme using fan wind at the lowest sound noise was studied. For the study, after measurement of the minimum sound noise of the fan and related temperature of the LED lamp through tests, experiments on temperature control of the LED lamp using the fan with various size of heat sinks was performed. Also, characteristics and relationship of heat sinks and fans are studied through experiments. To reduce the fan sound noise, a method of reducing the operation time with optimal size of the heat sink was studied.

Electroluminescence Spectral Imaging in Polymer Blend Light Emitting Diodes

2005 ◽  
Vol 871 ◽  
Author(s):  
Noriyuki Takada ◽  
Kiyohiko Tsutsumi ◽  
Toshihide Kamata
Keyword(s):  
Polymer Blend ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Spectral Imaging ◽  
Two Dimensional ◽  
Light Emitting ◽  
Spectroscopy System

AbstractThe spectral imaging for electroluminescence (EL) characterization in the light emitting diode (LED) based on blends of poly[2,7-(9,9-di-n-octylfluorene)] (PFO) and poly[2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)amino)-1,4-phenylene) ] (TFB) was performed using the two dimensional imaging micro-spectroscopy system. We found that EL spectral images varied with increasing applied voltages. The origin for such variation of EL spectral images will be discussed in this report.

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