Purely organic molecules with thermally activated delayed fluorescence (TADF) hold an advantage of high exciton utilization in organic light-emitting diodes (OLEDs). However, robust TADF materials with emission peaks over 600 nm are still insufficient due to strong non-radiative decay according to energy-gap law. Herein, tailor-made red TADF molecules comprised of an electron-withdrawing pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile core and various electron-donating triarylamines are developed. These molecules can form intramolecular hydrogen-bonding, which is conducive to improving emission efficiency and promoting horizontal orientation by increasing molecular rigidity and planarity. They show near infrared (NIR) emissions (692–710 nm) in neat films and red delayed fluorescence (606–630 nm) with high photoluminescence quantum yields (73–90%) in doped films, and prefer horizontal orientation with large horizontal dipole ratios in films, rendering high optical out-coupling factors (0.39–0.41). Their non-doped OLEDs exhibit NIR lights (716–748 nm) with maximum external quantum efficiencies ( η ext,max s) of 1.0–1.9%. And their doped OLEDs radiate red lights (606–648 nm) and achieve outstanding η ext,max s of up to 31.5%, which is the highest value for TADF materials emitting over 600 nm ever reported. These red TADF materials should have great potentials in displays and lighting devices.
https://ift.tt/3DwoA3t
π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton, exhibiting through-space charge transfer emission and thermally activated delayed fluorescence effect for white electroluminescence with state-of-the-art power efficiency of 58.9 lm W−1 by solution process.
Abstract
π-Stacked dendrimers consisting of cofacially aligned donors and acceptors are developed by introducing three dendritic teracridan donors with orthogonal configuration and three triazine acceptors in periphery of hexaphenylbenzene skeleton. The dendritic structure and orthogonal configuration of teracridan not only make their outer acridan segments approaching to acceptor in close distance, but also fix donor and acceptor in face-to-face alignment, leading to through-space charge transfer emission with thermally activated delayed fluorescence (TADF) effect. By regulating charge transfer strength via substituent effect of acceptor, emission color of the dendrimers can be tuned from blue to yellow/red region. Solution-processed two-color white organic light-emitting diodes (OLEDs) based on blue and yellow π-stacked donor–acceptor dendrimers exhibit the maximum external quantum efficiency of 20.6 % and maximum power efficiency of 58.9 lm W−1, representing the state-of-the-art efficiency for all-TADF white OLEDs by solution process.
https://ift.tt/2SMTd21
Multiple‐resonance (MR) organic emitters bearing small full‐width at half‐maximums (FWHMs) are of general interest in organic light‐emitting diodes. Indolo[3,2,1‐ jk ]carbazole (ICz) embedded MR‐fluorophors have demonstrated extremely small FWHMs, yet in the violet region with low electroluminescence efficiency. Herein, a strategic implementation of ICz subunits into MR fluorophors is proposed by taking advantage of the synergetic effect of para ‐positioned nitrogen atoms to enhance electronic coupling to decrease emitting energy gap. Deep blue emitters peaking at 441 and 447 nm with FWHMs of only 18 and 21 nm are thereof obtained respectively, accompanied by ~90% photo‐luminance quantum yields. With the assistance of a thermally activated delayed fluorescence sensitizer to recycle excitons, the corresponding narrowband electroluminescent devices show unprecedent high maximum external quantum efficiencies of 32.0% and 34.7% with CIE y of 0.10 and 0.085, respectively.
https://ift.tt/2ND9CDP
Pure green emitters are essential for realizing an ultrawide color gamut in next‐generation displays. Herein, by fusing the difficult‐to‐access aza‐aromatics onto B (boron)‐N (nitrogen) skeleton, a novel hybridized multi‐resonance and charge transfer (HMCT) molecule AZA‐BN was successfully synthesized through an effective one‐shot multiple cyclization method. AZA‐BN shows pure green fluorescence with photo‐luminance quantum yield of almost unity (99.7%). The corresponding green device exhibits a maximum external quantum efficiency and power efficiency of 28.2% and 121.7 lm W ‐1 , respectively, with a full width half maximum (FWHM) of merely 30 nm and Commission Internationale de l’Eclairage (CIE) coordinate y of 0.69: representing the purest green bottom‐emitting organic light‐emitting diode.
https://ift.tt/38q4xos
The design and synthesis of organic materials with narrowband emission feature in longer wavelength region beyond 510 nm remain a great challenge. For constructing narrowband green emitters, we propose a unique molecular design strategy based on frontier molecular orbital engineering ( FMOE ), which can ingeniously integrate the advantages of twisted donor–acceptor (D–A) structure and multiple resonance (MR) delayed fluorescence skeleton. By attaching an auxiliary donor to a MR skeleton, a novel molecule with twisted D–A and MR structure characteristics is formed. Importantly, remarkable red‐shift of emission maximum and narrowband spectrum are simultaneously achieved. The target molecule is employed as emitter to fabricate green organic light‐emitting devices (OLEDs) with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.23, 0.69) and maximum external quantum efficiency (EQE) of 27.0%.
https://ift.tt/2zsuUNg
For example a substance that is coated on an electrode glows green when a current is applied to the electrode.
Is it valid for me to say that the reason the substance glows is because energy from the current excites the electrons in the substance to a higher energy state? Once the electrons relax to ground state they will release energy in the form of photons.
If the wavelengths of these photons are within the visible range on the electromagnetic spectrum, we will see light.
Do all types of luminescence use the same principle of atomic absorption and emission?
Derivatives based on anthryleno[1,2‐b]pyrazine‐2,3‐dicarbonitrile ( DCPA) are used as luminescent materials, to realize near‐infrared (NIR) electroluminescence. By functionalizing DCPA with aromatic amine donors, two emitters named DCPA‐TPA and DCPA‐BBPA are designed and synthesized. Both molecules have large dipole moments due to the strong intramolecular charge transfer interactions between the amine donors and the DCPA acceptor. Thus, compared with doped films, the emission of neat films of DCPA‐TPA and DCPA‐BBPA can fully fall into the NIR region (>700 nm) with increasing surrounding polarity by increasing doping ratio. Moreover, the non‐doped devices based on DCPA‐TPA and DCPA‐BBPA provide NIR emission with peaks at 838 and 916 nm, respectively. A maximum radiannce of 20707 mW Sr ‐1 m ‐2 was realized for the further optimized device based on DCPA‐TPA . This work provides a simple and efficient strategy of molecular design for developing NIR emitting materials.
https://ift.tt/3a8RnNu
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c10081
Minlang Yang, In Seob Park, and Takuma Yasuda
https://ift.tt/32fwFbG
Are there any homebrew ways to check solar panels ? I know that there are commercial contractors who can do electroluminescence string tests. What they do - they connect a power source to string or one panel and it start emitting near IR, then they capture this with camera and perform image processing finding black holes. So for small amount of panels image processing can be skipped, camera can be a 4k security cam without IR cut filter but power source confuses me - if I want to check whole string I need to have ~600V power source with regulated I, not a cheap thing. Any other ideas ? Goal is to control panels degradation and periodic control after hail
https://preview.redd.it/ksn5gy4cdhh41.jpg?width=1296&format=pjpg&auto=webp&s=904ae6e825750c66920702877db0aca2b0b39897
Let′s twist again: Axially chiral molecules with thermally activated delayed fluorescence and circularly polarized electroluminescence (CPEL) are presented. CP‐OLEDs based on these molecules display high efficiencies and blue CPEL with large gEL values.
Abstract
The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is proposed. A pair of chiral stable enantiomers, (−)‐(S)‐Cz‐Ax‐CN and (+)‐(R)‐Cz‐Ax‐CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π‐conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (ΔEST) of 0.029 eV and mirror‐image circularly polarized luminescence (CPL) activities with large glum values. Notably, CP‐OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with gEL values of −1.2×10−2 and +1.4×10−2, respectively. These are the first CP‐OLEDs based on TADF‐active enantiomers with efficient blue CPEL.
https://ift.tt/3988yNY
Hi all,
Recently I was going through a bunch of electronic "junk" and recovered a small EL panel from a Ritetemp digital thermostat (digital; no mercury..my mercury theromostat has been recycled as a temp-sensitive switch).
I have no clue what exactly I'm going to do with it; but my first concern is how to power it. I did some generic research and found they all use 120VAC with a high(er) frequency.
Is that pretty typical of EL panels? I've seen a ton of designs for the supplies and I have no problem with understanding what I'm doing there; I just want to verify that the "120VAC at around 400hz" is "standard" for these devices. I'm seeing that all over the place; so it leads me to think it is. I've just never worked with them.
It doesn't have any identifying maarks on it other than what I suspect is a part number, SEC04043BBY; and 04110130 in a faux-seven-segment font that I'm sure is a lot/date information.
Edit: after several failed 555 based circuits; I got flawless operation using a very simple blocking oscillator and transformer.
A strategic implementation of indolo[3,2,1‐jk]carbazole units into polycyclic heteroaromatics is proposed, making use of not only the multi‐resonance for narrowband emission but also the enhanced electronic coupling of para‐positioned nitrogen atoms to narrow energy gaps. The corresponding emitters show narrowband deep‐blue electroluminance and high efficiencies when assisted by a sensitizer with thermally activated delayed fluorescence.
Abstract
Multiple‐resonance (MR) organic emitters bearing small full‐width at half‐maximum (FWHMs) are of general interest in organic light‐emitting diodes. Indolo[3,2,1‐jk]carbazole (ICz) embedded MR‐fluorophors have demonstrated extremely small FWHMs, yet in the violet region with low electroluminescence efficiency. Herein, a strategic implementation of ICz subunits into MR fluorophors is proposed by taking advantage of the synergetic effect of para‐positioned nitrogen atoms to enhance electronic coupling to decrease emitting energy gap. Deep blue emitters peaking at 441 and 447 nm with FWHMs of only 18 and 21 nm are thereof obtained, respectively, accompanied by ≈90 % photo‐luminance quantum yields. With the assistance of a thermally activated delayed fluorescence sensitizer to recycle excitons, the corresponding narrowband electroluminescent devices show unprecedent high maximum external quantum efficiencies of 32.0 % and 34.7 % with CIEy of 0.10 and 0.085, respectively.
https://ift.tt/2ND9CDP
By fusing aza‐aromatics onto a B−N skeleton, a hybridized multi‐resonance charge‐transfer molecule AZA‐BN was synthesized. The AZA‐BN device exhibits narrow‐band green electroluminescence with a maximum external quantum efficiency/CIE coordinate y of 28.2 %/0.69, representing the purest green bottom‐emitting organic light‐emitting diode.
Abstract
Pure green emitters are essential for realizing an ultrawide color gamut in next‐generation displays. Herein, by fusing the difficult‐to‐access aza‐aromatics onto B (boron)–N (nitrogen) skeleton, a hybridized multi‐resonance and charge transfer (HMCT) molecule AZA‐BN was successfully synthesized through an effective one‐shot multiple cyclization method. AZA‐BN shows pure green fluorescence with photoluminance quantum yield of 99.7 %. The corresponding green device exhibits a maximum external quantum efficiency and power efficiency of 28.2 % and 121.7 lm W−1, respectively, with a full width half maximum (FWHM) of merely 30 nm and Commission Internationale de l'Eclairage (CIE) coordinate y of 0.69, representing the purest green bottom‐emitting organic light‐emitting diode.
https://ift.tt/38q4xos
By fusing aza‐aromatics onto a B−N skeleton, a hybridized multi‐resonance charge‐transfer molecule AZA‐BN was synthesized. The AZA‐BN device exhibits narrow‐band green electroluminescence with maximum external quantum efficiency/CIE coordinate y of 28.2 %/0.69, representing the purest green bottom‐emitting organic light‐emitting diode.
Abstract
Pure green emitters are essential for realizing an ultrawide color gamut in next‐generation displays. Herein, by fusing the difficult‐to‐access aza‐aromatics onto B (boron)–N (nitrogen) skeleton, a hybridized multi‐resonance and charge transfer (HMCT) molecule AZA‐BN was successfully synthesized through an effective one‐shot multiple cyclization method. AZA‐BN shows pure green fluorescence with photoluminance quantum yield of 99.7 %. The corresponding green device exhibits a maximum external quantum efficiency and power efficiency of 28.2 % and 121.7 lm W−1, respectively, with a full width half maximum (FWHM) of merely 30 nm and Commission Internationale de l'Eclairage (CIE) coordinate y of 0.69, representing the purest green bottom‐emitting organic light‐emitting diode.
https://ift.tt/38q4xos
A molecular design strategy based on frontier molecular orbital engineering (FMOE) has been developed for constructing narrowband green emitters. Combining the advantages of twisted donor–acceptor structure and multiple resonance skeleton has led to an OLED that exhibits a strong narrowband green emission with CIE of (0.23, 0.69) and a maximum external quantum efficiency of 27.0 %.
Abstract
The design and synthesis of organic materials with a narrow emission band in the longer wavelength region beyond 510 nm remain a great challenge. For constructing narrowband green emitters, we propose a unique molecular design strategy based on frontier molecular orbital engineering (FMOE), which can integrate the advantages of a twisted donor–acceptor (D‐A) structure and a multiple resonance (MR) delayed fluorescence skeleton. Attaching an auxiliary donor to a MR skeleton leads to a novel molecule with twisted D‐A and MR structure characteristics. Importantly, a remarkable red‐shift of the emission maximum and a narrowband spectrum are achieved simultaneously. The target molecule has been employed as an emitter to fabricate green organic light‐emitting diodes (OLEDs) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.69) and a maximum external quantum efficiency (EQE) of 27.0 %.
https://ift.tt/2zsuUNg
