Enhancing performance for blue TADF emitters by introducing intramolecular CH⋯N hydrogen bonding between donor and acceptor

Use of Pyrimidine and Pyrazine Bridges as a Design Strategy To Improve the Performance of Thermally Activated Delayed Fluorescence Organic Light Emitting Diodes

“…We hypothesize that the intramolecular hydrogen bonding within the investigated emitters contributes to improvements in both the EQE max and efficiency roll-off as compared to our previously reported pyridine analogues with observations in line with those found in the literature. 31,32 On the other hand, the pDTCz-3DPyS:DPEPO and pDTCz-2DPyS:DPEPO devices show sharp blue EL spectra. While device D1 shows a slightly redshifted λ EL of 461 nm compared to pDTCz-3DPyS:DPEPO (λ EL = 452 nm) and a similar EL maximum to pDTCz-2DPyS:DPEPO (λ EL = 466 nm), its spectrum is broader, reflected by the larger full width at half maximum (FWHM).…”

Intramolecular Hydrogen Bonding in Thermally Activated Delayed Fluorescence Emitters: Is There Evidence Beyond Reasonable Doubt?

“…In other similar reports DFT is often used in a similar capacity as X-ray structures, with short N···H distances used to support the assertion of intramolecular H-bonding. 38 , 45 , 47 , 48 , 50 − 54 , 57 , 63 As noted above though, attractive interactions are not the only molecular feature that can cause short N···H interatomic distances, and so their presence in calculations does not immediately confirm an H-bonding interaction.…”

“…Incorporation of heteroatoms to induce attractive intramolecular interactions, most commonly N···H hydrogen bonds, is also now frequently reported (see Supporting Information section 2 for selected relevant examples). 37 − 57 , 63 …”

Theoretical studies on the excited-state properties of thermally activated delayed fluorescence molecules with aggregation induced emission

“…41 As mentioned above, the intramolecular hydrogen bond can increase the planarity, this could further increase the overlap between the HOMO and the LUMO with increased photoluminescence quantum yield and energy gap (Δ E ST ) between S 1 and T 1 . 42,43 Based on the characteristics of studied D1–A–D2 type molecules, there is almost no distribution for the HOMO on D1. Although intramolecular hydrogen bond (C–H⋯N), as mentioned in Section 4.1.2, is determined between the D1 and A, it has no influence on the distributions of the HOMO and LUMO.…”

“…41 As mentioned above, the intramolecular hydrogen bond can increase the planarity, this could further increase the overlap between the HOMO and the LUMO with increased photoluminescence quantum yield and energy gap (DE ST ) between S 1 and T 1 . 42,43 Based on the characteristics of studied D1-A-D2 type molecules, there is almost no distribution for the HOMO on D1.…”