Highly efficient organic light-emitting diodes from delayed fluorescence
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Citations
Luminescence in Crystalline Organic Materials: From Molecules to Molecular Solids
4CzIPN-tBu-Catalyzed Proton-Coupled Electron Transfer for Photosynthesis of Phosphorylated N-Heteroaromatics.
Mechanically triggered fluorescence/phosphorescence switching in the excimers of planar trinuclear copper(I) pyrazolate complexes.
Unicolored phosphor-sensitized fluorescence for efficient and stable blue OLEDs
The Role of Reverse Intersystem Crossing Using a TADF-Type Acceptor Molecule on the Device Stability of Exciplex-Based Organic Light-Emitting Diodes.
References
The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals
Toward reliable density functional methods without adjustable parameters: The PBE0 model
The influence of polarization functions on molecular orbital hydrogenation energies
Very high-efficiency green organic light-emitting devices based on electrophosphorescence
Nearly 100% internal phosphorescence efficiency in an organic light emitting device
Related Papers (5)
Frequently Asked Questions (15)
Q2. What is the critical point of the molecular design?
11 The critical point of the molecular design is the compatibility of a small EST ~ 0 eV and a reasonable radiative decay rate of over 10 6 /s that overcomes competitive non-radiative decay paths, leading to highly luminescent TADF materials.
Q3. What is the effect of the EL design on the fluorescence efficiency of organic materials?
With proper molecular design, the energy gap between the two excited states, i.e., singlet (S1) and triplet (T1) excited states, are minimized, promoting very efficient spin up-conversion from T1 to S1 states (reverse intersystem crossing (ISC)) while maintaining a rather high radiative decay rate of >10 6 /s, leading to a high fluorescence efficiency of >90%.
Q4. What is the simplest way to obtain a CDCB?
The aromatic nucleophilic substitution reaction (SNAr) of an anion of carbazole, generated by treatment with NaH and dicyanobenzene at room temperature, yielded CDCBs.
Q5. What is the cost advantage of CDCBs?
CDCBs were synthesized through a one-step-only reaction from commerciallyavailable starting materials without the addition of palladium or other rare metal catalysts, indicating that CDCBs also have cost advantages.
Q6. What is the effect of the inhibition of large geometry change on CDCBs?
The change in the geometry of CDCBs between S0 and S1 states occurs not all over the molecule but only in the central dicyanobenzene unit, and the inhibition of large geometry change leads to a high quantum efficiency.
Q7. What is the effect of iridium phenylpyridine on EL?
In 1999, Forrest and Thompson’s group first demonstrated efficient electrophosphorescence using iridium phenylpyridine complexes that promote an efficient radiative decay rate of ~10 6 /s by taking advantage of a heavy metal effect, strong spin-orbital coupling 8 .
Q8. What is the PL spectra of CDCBs in toluene?
In addition, the authors note that while the oscillator strength for the ground states of CDCBs estimated by TD-DFT is a rather small value of less than 0.1, the peculiar geometric characteristics discussed in this paragraph are consistent with the suppression of the non-radiative decay, leading to the high PLQY.
Q9. What is the reason for the small geometry relaxation of 4CzIPN?
The lack of the quinoid-type deformation accounts for the small geometry relaxation of 4CzIPN compared with those of 4CzTPN and 4CzPN.
Q10. What is the effect of the reverse ISC process on the delayed component?
On the other hand, the delayed component monotonically decreases with a decrease in temperature, since the reverse ISC process becomes the rate-determining step, similar to the temperature dependence of tin(IV) fluoride-porphyrin complexes, which are typical TADF emitters 10 .
Q11. What is the kRISC of the orange and sky-blue OLEDs?
In addition, the orange and sky-blue OLEDs show higher external EL quantum efficiency of 11.2±1% and 8.0±1%, respectively, compared to those of conventional fluorescence-based OLEDs.
Q12. What was the reaction reaction of a carbazolyl anion and a dicyan?
CDCBs were synthesized by reaction of a carbazolyl anion and a fluorinated dicyanobenzene at room temperature for 10 h under a nitrogen atmosphere.
Q13. What is the simplest way to achieve a high PL efficiency?
Since very small orbital overlapping generally results in virtually no emission as is shown in benzophenone derivatives, one assumes that high PL efficiency could never be obtained with molecules having small EST; however, the authors have overcome this issue.
Q14. How much efficiency can be achieved with a high-efficiency phosphorescent OLED?
Using these unique molecules, the authors realized a very3high external EL efficiency of over 19% that is comparable with those of high-efficiency phosphorescence-based OLEDs.
Q15. Why is the first-order mixing coefficient inversely proportional to the EST?
This is because the first-order mixing coefficient between singlet and triplet states () is inversely proportional to the EST as described by 18 :STSOEH (2)where HSO is the spin-orbital interaction.