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Recent Advances in Conjugated TADF Polymer Featuring in Backbone-Donor/Pendant-Acceptor Structure: Material and Device Perspectives
摘要： Along with the persistent research interest in organic light-emitting diode (OLED) display and lighting technology, a new studying topic is now focused on developing thermally activated delayed fluorescence (TADF) polymer emitters, with the purpose to achieve high-performance cost-effective, solution-processed OLEDs (s-OLEDs) purely from fluorescent-type materials. However, research in this topic is in its infancy about the designing rules of polymer structures, photophysical mechanisms and the correlated devices. In this Personal Account, mainly from our personal experience we will shortly introduce the historical developments, status and perspectives about one representative kinds of TADF polymers, i. e. the conjugated TADF polymers featuring in backbone-donor/pendant-acceptor (BDPA) structure scaffold, which shows very promising electroluminescent (EL) performance even using simple s-OLED structure. Special attention is focused on illustrate the molecular designing & synthesis motivation, chemistry & device tactics towards solving the limiting factors about the quantum yields and aggregation-quenching tendency in solid states. Further challenges and strategies towards optimizing their overall EL performance, e. g. simultaneous achieving extremely high external quantum efficiency, power efficiency and low roll-off rate, are also discussed.
关键词： thermally activated delayed fluorescence,exciplex,solution-processed,polymer,organic light-emitting diodes
更新于2025-09-10 09:29:36
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Highly efficient thermally activated delayed fluorescence with slow reverse intersystem crossing
摘要： We report an efficient luminescent molecule exhibiting thermally activated delayed fluorescence with a long-delayed fluorescence lifetime of 0.8 ms. Although the reverse intersystem crossing rate constant is small at 2.1 × 103 s?1, the molecule shows a high photoluminescence quantum yield of 89±2%, indicating the suppression of nonradiative decay from the triplet state.
关键词： Long triplet lifetime,Thermally activated delayed fluorescence (TADF),Reverse intersystem crossing (RISC)
更新于2025-09-10 09:29:36
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Kinetic Modelling of Transient Photoluminescence from Thermally Activated Delayed Fluorescence
摘要： A simplified state model and associated rate equations are used to extract the reverse intersystem crossing and other key rate constants from transient photoluminescence measurements of two high performance thermally activated delayed fluorescence materials. The values of the reverse intersystem crossing rate constant are in close agreement with established methods, but do not require a priori assumption of exponential decay kinetics, nor any additional steady state measurements. The model is also applied to measurements at different temperatures and found to reproduce previously reported thermal activation energies for the thermally activated delayed fluorescence process. Transient absorption measurements provide independent confirmation that triplet decay channels (neglected here) have no adverse effect on the fitting.
关键词： Thermally Activated Delayed Fluorescence,Transient Photoluminescence,Reverse Intersystem Crossing,Kinetic Modelling
更新于2025-09-10 09:29:36
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Heteroleptic Copper(I) Complexes Prepared from Phenanthroline and Bis-Phosphine Ligands: Rationalization of the Photophysical and Electrochemical Properties
摘要： The electronic and structural properties of ten heteroleptic [Cu(NN)(PP)]+ complexes have been investigated. NN indicates 1,10-phenanthroline (phen) or 4,7-diphenyl-1,10-phenanthroline (Bphen); each of these ligands is combined with five PP bis-phosphine chelators, i.e., bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)benzene (dppb), and bis[(2-diphenylphosphino)phenyl] ether (POP). All complexes are mononuclear, apart from those based on dppm, which are dinuclear. Experimental data—also taken from the literature and including electrochemical properties, X-ray crystal structures, UV?vis absorption spectra in CH2Cl2, luminescence spectra and lifetimes in solution, in PMMA, and as powders—have been rationalized with the support of density functional theory calculations. Temperature dependent studies (78?358 K) have been performed for selected complexes to assess thermally activated delayed fluorescence. The main findings are (i) dependence of the ground-state geometry on the crystallization conditions, with the same complex often yielding different crystal structures; (ii) simple model compounds with imposed C2v symmetry ([Cu(phen)(PX3)2]+; X = H or CH3) are capable of modeling structural parameters as a function of the P?Cu?P bite angle, which plays a key role in dictating the overall structure of [Cu(NN)(PP)]+ complexes; (iii) as the P?Cu?P angle increases, the energy of the metal-to-ligand charge transfer absorption bands linearly increases; (iv) the former correlation does not hold for emission spectra, which are red-shifted for the weaker luminophores; (v) the larger the number of intramolecular π-interactions within the complex in the ground state, the higher the luminescence quantum yield, underpinning a geometry locking effect that limits the structural flattening of the excited state. This work provides a general framework to rationalize the structure?property relationships of [Cu(NN)(PP)]+, a class of compounds of increasing relevance for electroluminescent devices, photoredox catalysis, and solar-to-fuels conversion, which so far have been investigated in an unsystematic fashion, eluding a comprehensive understanding.
关键词： electrochemical properties,bis-phosphine ligands,photophysical properties,phenanthroline,thermally activated delayed fluorescence,density functional theory,heteroleptic copper(I) complexes
更新于2025-09-09 09:28:46
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Photo-Physical Properties of Thermally Activated Delayed Fluorescent Materials upon Distortion of Central Axis of Donor Moiety
摘要： In this study, we showed the distortion of central axis of donor moiety can switch critically the rate of reverse intersystem crossing (kRISC) process, which is the trigger point to modulate the lifetime of delayed fluorescence. To achieve kRISC what we desired (105 to 106 s-1) in a series of donor-acceptor-donor (D-A-D) type thermally activated delayed fluorescence (TADF) materials, the donor groups (phenoxazine and phenothiazine) was selectively introduced. Maintaining the near orthogonality between donor and acceptor (benzonitrile) moiety, the occurrence of the distortion of central axis of donor moiety could make the effect of locally excited triplet state (3LE). In other words, the interaction between 3LE and the charge transfer counterparts (i.e., 1CT and 3CT) contributes an opposite propensity of kRISC for each target TADF materials when those are dissolved in solution and condensed in solid-state. Herein, we have theoretically and experimentally shown the photo-physical behavior of common D-A-D type TADF upon the different system.
关键词： Reverse Intersystem Crossing,Thermally Activated Delayed Fluorescence,Benzonitrile,Phenoxazine,Donor-Acceptor-Donor,Phenothiazine
更新于2025-09-09 09:28:46
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Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes
摘要： A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.
关键词： ambipolar,Donor-Acceptor,Thermally Activated Delayed Fluorescence,exciplex,Organic Electronics,patterning,thermal evaporation,Issue 141,OLED,Engineering
更新于2025-09-09 09:28:46
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Mechanical Insights into Aggregation-Induced Delayed Fluorescence Materials with Anti-Kasha Behavior
摘要： Organic materials with aggregation-induced delayed fluorescence (AIDF) have exhibited impressive merits for improving electroluminescence efficiency and decreasing efficiency roll-off of nondoped organic light-emitting diodes (OLEDs). However, the lack of comprehensive insights into the underlying mechanism may impede further development and application of AIDF materials. Herein, AIDF materials consisting of benzoyl serving as an electron acceptor, and phenoxazine and fluorene derivatives as electron donors are reported. They display greatly enhanced fluorescence with increased delayed component upon aggregate formation. Experimental and theoretical investigations reveal that this AIDF phenomenon can be rationally ascribed to the suppression of internal conversion and the promotion of intersystem crossing in solid. Moreover, the theoretical calculations disclose that the efficient solid-state delayed fluorescence originates from the higher energy electronic excited state (e.g., S2) rather than the lowest energy-excited state (S1), demonstrating an anti-Kasha behavior. The excellent AIDF property allows high exciton utilization and thus superb performance of OLEDs using these new materials as light-emitting layers.
关键词： aggregation-induced delayed fluorescence,anti-Kasha emission,intersystem crossing,internal conversion,organic light-emitting diodes
更新于2025-09-09 09:28:46
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Insights into the Efficient Intersystem Crossing of Bodipy-Anthracene Compact Dyads with Steady State and Time-Resolved Optical/Magnetic Spectroscopies and Observation of the Delayed Fluorescence
摘要： Spin-orbit charge transfer induced intersystem crossing (SOCT-ISC) is of particular interest for preparation of heavy atom-free triplet photosensitizers. Up to now examples for SOCT-ISC dyads are limited and electron donor/acceptor SOCT-ISC dyads showing strong visible light-harvesting are rare. Herein we studied the photophysics of a series of Bodipy-anthracene (BDP-An) compact dyads, especially the triplet state electron spin dynamics with the time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The electronic coupling matrix elements (VDA*) between the 1CT (charge transfer) state and 1LE (locally excited) state are in the range 773 cm?1 – 1545 cm?1. For one dyad, we observed three triplet states simultaneously with TREPR, i.e. the triplet states confined on the anthracene (3An) and the Bodipy (3BDP) moieties, as well as a 3CT state. Based on the electron spin polarization (ESP) of these three triplet states and the optical experiments, the SOCT-ISC mechanism is confirmed and the RP-ISC mechanism as the main ISC channel was excluded. Triplet-triplet annihilation (TTA) induced delayed fluorescence was observed for the dyads, which is rare for Bodipy fluorophores.
关键词： intersystem crossing,Bodipy-anthracene dyads,Spin-orbit charge transfer,time-resolved electron paramagnetic resonance,delayed fluorescence,triplet states
更新于2025-09-09 09:28:46
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Importance of Chromophore Rigidity on the Efficiency of Blue Thermally Activated Delayed Fluorescence Emitters
摘要： Four new symmetrical donor?acceptor?donor (D?A?D)-type molecules are reported with diphenylamine (DPA) or 10,11-dihydro-5H-dibenz[b,f ]azepine (Az) as electron donors and 9,9-dimethylthioxanthene-S,S-dioxide (TXO2) as the electron acceptor. The donors are attached at different positions on the acceptor core: either para or meta to the sulfone unit. This series provides new insights into the effects of chromophore rigidity/flexibility on the efficiency of thermally activated delayed fluorescence (TADF). The molecules have been characterized by X-ray crystallography, by in-depth photophysical studies, and by theoretical calculations. The clear differences observed in the photophysical properties when using DPA or Az as a donor are shown to originate from different geometries of the donor unit which, in turn, influence the geometry of the nitrogen lone pair and the donating strength of the corresponding fragment. Thus, a para-substituted Az derivative demonstrated blue TADF in polar media, while the compounds with more flexible DPA units did not show delayed fluorescence. To obtain deep-blue emitters, weaker donating units are needed. A more flexible donor unit leads to increased local excited state (donor) LE emission and reduced TADF. However, a certain amount of flexibility has to be present to ensure deep-blue TADF.
关键词： chromophore rigidity,blue emitters,donor-acceptor-donor,photophysical properties,thermally activated delayed fluorescence
更新于2025-09-04 15:30:14
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Synthesis of linear and V‐shaped carbazolyl‐substituted pyridine‐3,5‐dicarbonitriles exhibiting efficient bipolar charge transport and E‐type fluorescence
摘要： Aiming to develop all-organic bipolar semiconductors with high charge mobility and efficient E-type fluorescence (so-called TADF) as environmentally-friendly light-emitting materials for optoelectronic applications, four noble metals-free dyes with linear and V-shapes were designed using accepting pyridine-3,5-dicarbonitrile and donating carbazole units. Exploiting donor-acceptor design strategy and using moieties with different donating and accepting abilities, TADF emitters with wide variety of molecular weights were synthesized for getting optimum combination of charge-transporting and fluorescent properties in one TADF molecule. Depending on molecule structures, different TADF emitters capable of emitting in the range from 453 to 550 nm with photoluminescence quantum yields up to 98% for the solutions in oxygen-free toluene were obtained. All compounds showed bipolar charge-transport. Hole mobility of 2.8×10-3 cm2/Vs at 7×105 V/cm was observed for the compound containing two di-tert-butyl-substituted carbazole moieties. The compounds were tested in both non-doped and doped organic light-emitting diodes using different hosts. It was shown that the developed TADF emitters are suitable for different colour devices with electroluminescence ranging from blue to yellow and with brightness, maximum current and external quantum efficiencies exceeding 10000 cd/m2, 15 cd/A, and 7%.
关键词： electroluminescence,substituent,delayed fluorescence,OLED
更新于2025-09-04 15:30:14