Browse
Submit Data
Databases
API
Help

Dataset Information

23 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Regiochemistry of Donor Dendrons Controls the Performance of Thermally Activated Delayed Fluorescence Dendrimer Emitters for High Efficiency Solution-Processed Organic Light-Emitting Diodes.

ABSTRACT: The potential of dendrimers exhibiting thermally activated delayed fluorescence (TADF) as emitters in solution-processed organic light-emitting diodes (OLEDs) has to date not yet been realized. This in part is due to a poor understanding of the structure-property relationship in dendrimers where reports of detailed photophysical characterization and mechanism studies are lacking. In this report, using absorption and solvatochromic photoluminescence studies in solution, the origin and character of the lowest excited electronic states in dendrimers with multiple dendritic electron-donating moieties connected to a central electron-withdrawing core via a para- or a meta-phenylene bridge is probed. Characterization of host-free OLEDs reveals the superiority of meta-linked dendrimers as compared to the already reported para-analogue. Comparative temperature-dependent time-resolved solid-state photoluminescence measurements and quantum chemical studies explore the effect of the substitution mode on the TADF properties and the reverse intersystem crossing (RISC) mechanism, respectively. For TADF dendrimers with similarly small ∆E_ST , it is observed that RISC can be enhanced by the regiochemistry of the donor dendrons due to control of the reorganization energies, which is a heretofore unexploited strategy that is distinct from the involvement of intermediate triplet states through a nonadiabatic (vibronic) coupling with the lowest singlet charge transfer state.

SUBMITTER: Sun D

PROVIDER: S-EPMC9284163 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Isomeric thermally activated delayed fluorescence emitters for highly efficient organic light-emitting diodes.

Project description:The isomeric strategy is an important design concept in molecular design that has a non-negligible influence on molecular properties. Herein, two isomeric thermally activated delayed fluorescence (TADF) emitters (NTPZ and TNPZ) are constructed with the same skeleton consisting of an electron donor and electron acceptor but different connection sites. Systematic investigations show that NTPZ exhibits a small energy gap, large up-conversion efficiency, low non-radiative decay, and high photoluminescence quantum yield. Further theoretical simulations reveal that the excited molecular vibrations play a key role in regulating the non-radiative decays of the isomers. Therefore, an NTPZ based OLED achieves better electroluminescence performances, such as a higher external quantum efficiency of 27.5% compared to a TNPZ based OLED (18.3%). This isomeric strategy not only provides an opportunity to deeply understand the relationship between substituent locations and molecular properties, but also affords a simple and effective strategy to enrich TADF materials.

| S-EPMC9906651 | biostudies-literature

Highly effective organic light-emitting diodes containing thermally activated delayed fluorescence emitters with horizontal molecular orientation.

Project description:In this study, we report new thermally activated delayed fluorescence (TADF) emitters, AcPYM (10,10'-(pyrimidine-2,5-diylbis(4,1-phenylene))bis(9,9-dimethyl-9,10-dihydroacridine)) and PxPYM (10,10'-(pyrimidine-2,5-diylbis(4,1-phenylene))bis(10H-phenoxazine)), by employing donor units at the 2,5-positions of the pyrimidine acceptor unit. The donor-acceptor-donor (D-A-D) units combined in the linear molecular structure of AcPYM or PxPYM enhanced the horizontally oriented alignment, and the horizontal transition dipole moments were realized by up to 87% in the host matrix. Organic light-emitting diodes (OLEDs) containing AcPYM and PxPYM emitters realized external quantum efficiencies (η ext) of 16.8% for blue and green emissions.

| S-EPMC9058249 | biostudies-literature

Blue organic light-emitting diodes realizing external quantum efficiency over 25% using thermally activated delayed fluorescence emitters.

Project description:Improving the performance of blue organic light-emitting diodes (OLEDs) is needed for full-colour flat-panel displays and solid-state lighting sources. The use of thermally activated delayed fluorescence (TADF) is a promising approach to efficient blue electroluminescence. However, the difficulty of developing efficient blue TADF emitters lies in finding a molecular structure that simultaneously incorporates (i) a small energy difference between the lowest excited singlet state (S1) and the lowest triplet state (T1), ΔE ST, (ii) a large oscillator strength, f, between S1 and the ground state (S0), and (iii) S1 energy sufficiently high for blue emission. In this study, we develop TADF emitters named CCX-I and CCX-II satisfying the above requirements. They show blue photoluminescence and high triplet-to-singlet up-conversion yield. In addition, their transition dipole moments are horizontally oriented, resulting in further increase of their electroluminescence efficiency. Using CCX-II as an emitting dopant, we achieve a blue OLED showing a high external quantum efficiency of 25.9%, which is one of the highest EQEs in blue OLEDs reported previously.

| S-EPMC5428273 | biostudies-literature

Highly Efficient Green and Red Narrowband Emissive Organic Light-Emitting Diodes Employing Multi-Resonant Thermally Activated Delayed Fluorescence Emitters.

Project description:Herein, we demonstrate how judicious selection of the donor decorating a central multi-resonant thermally activated delayed fluorescence (MR-TADF) core based on DiKTa can lead to very high-performance OLEDs. By decorating the DiKTa core with triphenylamine (TPA) and diphenylamine (DPA), 3TPA-DiKTa and 3DPA-DiKTa exhibit bright, narrowband green and red emission in doped films, respectively. The OLEDs based on these emitters showed record-high performance for this family of emitters with maximum external quantum efficiencies (EQEmax ) of 30.8 % for 3TPA-DiKTa at λEL of 551 nm and 16.7 % for 3DPA-DiKTa at λEL =613 nm. The efficiency roll-off in the OLEDs was improved significantly by using 4CzIPN as an assistant dopant in hyperfluorescence (HF) devices. The outstanding device performance has been attributed to preferential horizontal orientation of the transition dipole moments of 3TPA-DiKTa and 3DPA-DiKTa.

| S-EPMC10100094 | biostudies-literature

Mulifunctional Dendritic Emitter: Aggregation-Induced Emission Enhanced, Thermally Activated Delayed Fluorescent Material for Solution-Processed Multilayered Organic Light-Emitting Diodes.

Project description:Thermally activated delayed fluorescence (TADF) materials emerged as promising light sources in third generation organic light-emitting diodes (OLED). Much effort has been invested for the development of small molecular TADF materials and vacuum process-based efficient TADF-OLEDs. In contrast, a limited number of solution processable high-molecular weight TADF materials toward low cost, large area, and scalable manufacturing of solution processed TADF-OLEDs have been reported so far. In this context, we report benzophenone-core carbazole dendrimers (GnB, n = generation) showing TADF and aggregation-induced emission enhancement (AIEE) properties along with alcohol resistance enabling further solution-based lamination of organic materials. The dendritic structure was found to play an important role for both TADF and AIEE activities in the neat films. By using these multifunctional dendritic emitters as non-doped emissive layers, OLED devices with fully solution processed organic multilayers were successfully fabricated and achieved maximum external quantum efficiency of 5.7%.

| S-EPMC5282576 | biostudies-literature

Design of efficient thermally activated delayed fluorescence blue host for high performance solution-processed hybrid white organic light emitting diodes.

Project description:Developing a solution-processible blue thermally activated delayed fluorescence (TADF) emitter for hybrid white organic light emitting diodes (WOLEDs) is still a challenge. In this work, two TADF blue emitters are designed and synthesized to explore a common strategy to qualify the small molecular TADF material as a solution-processible blue host. Systematic studies find that the molecular encapsulation by introducing unconjugated carbazoles as steric shields not only keeps the intrinsic TADF feature unchanged, but also effectively suppress the intermolecular interaction induced exciton quenching, which makes the material more efficient for solution-processing. The optimized solution-processed hybrid WOLEDs based on the encapsulated TADF blue host realized a highly efficient device performance with a maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 45.6 cd A-1, 40.9 lm W-1 and 17.0%, respectively, which are three times higher in device efficiency and twenty times higher in device lifetime than the corresponding device with an unencapsulated TADF blue host. Furthermore, the obtained device exhibits a high electroluminescence (EL) above 20 000 cd m-2 and a stable EL spectrum with nearly unchanged Commission International de L'Eclairage (CIE) coordinate at a wide range of applied voltages. These results clearly demonstrate that the molecular encapsulation of the TADF blue host is a superior and promising strategy to achieve high performance and color stable solution-processed hybrid WOLEDs.

| S-EPMC6428138 | biostudies-literature

Operando ESR observation in thermally activated delayed fluorescent organic light-emitting diodes.

Project description:Organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) materials have advantages over OLEDs using conventional fluorescent materials or high-cost phosphorescent materials, including higher efficiency and lower cost. To attain further high device performance, clarifying internal charge states in OLEDs at a microscopic viewpoint is crucial; however, only a few such studies have been performed. Here, we report a microscopic investigation into internal charge states in OLEDs with a TADF material by electron spin resonance (ESR) at a molecular level. We observed operando ESR signals of the OLEDs and identified their origins due to a hole-transport material PEDOT:PSS, gap states at an electron-injection layer, and a host material CBP in the light-emitting layer by performing density functional theory calculation and studying thin films used in the OLEDs. The ESR intensity varied with increasing applied bias before and after the light emission. We find leakage electrons in the OLED at a molecular level, which is suppressed by a further electron-blocking layer MoO3 between the PEDOT:PSS and light-emitting layer, resulting in the enhancement of luminance with a low-voltage drive. Such microscopic information and applying our method to other OLEDs will further improve the OLED performance from the microscopic viewpoint.

| S-EPMC10333204 | biostudies-literature

Thermally Activated Delayed Fluorescence Host for High Performance Organic Light-Emitting Diodes.

Project description:Thermally activated delayed florescence (TADF) materials can be an efficient host in organic LED (OLED). It is because it is possible to couple energetically the emission energy level of a dopant to the energy levels in the TADF material. In this work fluorescent emitters 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5 H,11H-10-(2-benzothiazolyl)quinolizino-9,9a,1gh coumarin (c545t) and 5,6,11,12-tetraphenyltetracene (rubrene) were used as dopants in a blended TADF host; tris(4-carbazoyl-9-ylphenyl)amine (TCTA) with 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine (Tm3PyBPZ). The blended TADF host has an energy difference between the singlet and triplet excited states (ΔEST) around 27 meV with the yield of reverse intersystem crossing (ФRISC) nearly 100%. This high ФRISC yield enhances the OLED performance with the c545t doped OLED having 11.9% external quantum efficiency and 10% for the rubrene doped OLED.

| S-EPMC5995865 | biostudies-literature

Excited-State Modulation in Donor-Substituted Multiresonant Thermally Activated Delayed Fluorescence Emitters.

Project description:Strategies to tune the emission of multiresonant thermally activated delayed fluorescence (MR-TADF) emitters remain rare. Here, we explore the effect of donor substitution about a MR-TADF core on the emission energy and the nature of the excited state. We decorate different numbers and types of electron-donors about a central MR-TADF core, DiKTa. Depending on the identity and number of donor groups, the excited state either remains short-range charge transfer (SRCT) and thus characteristic of an MR-TADF emitter or becomes a long-range charge transfer (LRCT) that is typically observed in donor-acceptor TADF emitters. The impact is that in three examples that emit from a SRCT state, Cz-DiKTa, Cz-Ph-DiKTa, and 3Cz-DiKTa, the emission remains narrow, while in four examples that emit via a LRCT state, TMCz-DiKTa, DMAC-DiKTa, 3TMCz-DiKTa, and 3DMAC-DiKTa, the emission broadens significantly. Through this strategy, the organic light-emitting diodes fabricated with the three MR-TADF emitters show maximum electroluminescence emission wavelengths, λEL, of 511, 492, and 547 nm with moderate full width at half-maxima (fwhm) of 62, 61, and 54 nm, respectively. Importantly, each of these devices show high maximum external quantum efficiencies (EQEmax) of 24.4, 23.0, and 24.4%, which are among the highest reported with ketone-based MR-TADF emitters. OLEDs with D-A type emitters, DMAC-DiKTa and TMCz-DiKTa, also show high efficiencies, with EQEmax of 23.8 and 20.2%, but accompanied by broad emission at λEL of 549 and 527 nm, respectively. Notably, the DMAC-DiKTa-based OLED shows very small efficiency roll-off, and its EQE remains 18.5% at 1000 cd m-2. Therefore, this work demonstrates that manipulating the nature and numbers of donor groups decorating a central MR-TADF core is a promising strategy for both red-shifting the emission and improving the performance of the OLEDs.

| S-EPMC9121343 | biostudies-literature

Highly Efficient and Stable Blue Organic Light-Emitting Diodes based on Thermally Activated Delayed Fluorophor with Donor-Void-Acceptor Motif.

Project description:Thermally activated delayed fluorophores (TADF) with donor-acceptor (D-A) structures always face strong conjugation between donor and acceptor segments, rendering delocalized new molecular orbitals that go against blue emission. Developing TADF emitters with blue colors, high efficiencies, and long lifetimes simultaneously is therefore challenging. Here, a D-void-A structure with D and A moieties connected at the void-position where the frontier orbital from donor and acceptor cannot be distributed, resulting in nonoverlap of the orbitals is proposed. A proof-of-the-concept TADF emitter with 3,6-diphenyl-9H-carbazole (D) connected at the 3'3-positions of 9H-xanthen-9-one (A), the void carbon-atom with no distribution of the highest occupied molecular orbital (HOMO) of A-segment, realizes more efficient and blue-shifted emission compared with the contrast D-A isomers. The deeper HOMO-2 of A is found to participate into conjugation rather than HOMO, providing a wider-energy-gap. The corresponding blue device exhibits a y color coordinate (CIEy ) of 0.252 and a maximum external quantum efficiency of 27.5%. The stability of this compound is further evaluated as a sensitizer for a multiple resonance fluorophore, realizing a long lifetime of ≈650 h at an initial luminance of 100 cd m-2 with a CIEy of 0.195 and a narrowband emission with a full-width-at-half-maxima of 21 nm.

| S-EPMC9036013 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data