A multilayered graphene hydrogel (MGH) membrane is used as an excellent barrier membrane for guided bone regeneration. The unique multilayered nanostructure of the MGH membrane results in improved material properties, which benefits protein adsorption, cell adhesion, and apatite deposition, and allows higher quality and fast bone regeneration.
Developing red thermally activated delayed fluorescence (TADF) emitters,a ttainable for both high-efficient red organic light-emitting diodes (OLEDs) and non-doped deep red/near-infrared (NIR) OLEDs,ischallenging. Now,two red emitters,B PPZ-PXZ and mDPBPZ-PXZ, with twisted donor-acceptor structures were designed and synthesized to study molecular design strategies of high-efficiency red TADF emitters.B PPZ-PXZ employs the strictest molecular restrictions to suppress energy loss and realizes red emission with aphotoluminescence quantum yield (F PL )of100 AE 0.8 %and external quantum efficiency (EQE) of 25.2 %i nadoped OLED.Its non-doped OLED has an EQE of 2.5 %owingto unavoidable intermolecular p-p interactions.mDPBPZ-PXZ releases two pyridine substituents from its fused acceptor moiety.A lthough mDPBPZ-PXZ realizes al ower EQE of 21.7 %i nt he doped OLED,i ts non-doped device shows asuperior EQE of 5.2 %with adeep red/NIR emission at peak of 680 nm.
Two
novel thermally activated delayed fluorescence (TADF) emitters, 3-phenylquinolino[3,2,1-de]acridine-5,9-dione (3-PhQAD) and 7-phenylquinolino[3,2,1-de]acridine-5,9-dione (7-PhQAD), were designed and synthesized
based on a rigid quinolino[3,2,1-de]acridine-5,9-dione
(QAD) framework. With the effective superimposed resonance effect
from electron-deficient carbonyls and electron-rich nitrogen atom,
both emitters realize significant TADF characteristics with small
ΔE
STs of 0.18 and 0.19 eV, respectively.
And, molecular relaxations were dramatically suppressed for both emitters
because of their conjugated structure. In the devices, 3-PhQAD realizes
superior performance with a maximum external quantum efficiency (EQE)
of 19.1% and a narrow full width at half-maximum (FWHM) of 44 nm,
whereas a maximum EQE of 18.7% and an extremely narrow FWHM of 34
nm are realized for 7-PhQAD. These superior results reveal that apart
from nitrogen and boron-aromatic systems, QAD framework can also act
as a TADF matrix with effective resonance effect, and QAD derivatives
are ideal candidates to develop TADF emitters with narrow FWHMs for
practical applications.
Highly
twisted electron donor (D)–electron acceptor (A)-type
thermally activated delayed fluorescence (TADF) emitters can achieve
high efficiency while suffering from serious structural relaxations
and broad emissions. Multiple resonance (MR)-type TADF emitters can
realize narrow emission. However, until now, only a few efficient
MR-emitting cores are reported and custom tunning of their emission
color remains a major challenge in their wider applications. In this
work, by combining the conventional TADF and MR-TADF designs, we demonstrate
that color tuning and narrowing the spectral width of conventional
TADF emission can be easily achieved simultaneously. We select a prototypical
carbonyl (CO)/N-based MR core as a backbone and attach it
with D segments of different electron-donating abilities and numbers
to obtain three different TADF emitters with emissions from sky blue
to green and orange-red while maintaining the narrow emission of the
original MR core. The corresponding sky blue, green, and orange-red
organic light-emitting diodes achieve maximum external quantum efficiencies
of 20.3, 27.3, and 26.3%, respectively, and narrow full widths at
half-maximum all below 0.28 eV. These results provide a new molecular
design strategy for developing narrowband TADF emitters with easily
tunable emissions covering the full visible range.
Nondoped organic light-emitting diodes (OLEDs) have drawn immense attention due to their merits of process simplicity, reduced fabrication cost, etc. To realize high-performance nondoped OLEDs, all electrogenerated excitons should be...
Developing red thermally activated delayed fluorescence (TADF) emitters for high‐performance OLEDs is still facing great challenge. Herein, three red TADF emitters, pDBBPZ‐DPXZ, pDTBPZ‐DPXZ, and oDTBPZ‐DPXZ, are designed and synthesized with same donor–acceptor (D‐A) backbone with different peripheral groups attaching on the A moieties. Their lowest triplet states change from locally excited to charge transfer character leading to significantly enhance reverse intersystem crossing process. In particular, oDTBPZ‐DPXZ exhibits efficient TADF feature and exciton utilization. It not only achieves an external quantum efficiency (EQE) of 20.1 % in red vacuum‐processed OLED, but also realize a high EQE of 18.5 % in a solution‐processed OLED, which is among the best results in solution‐processed red TADF OLEDs. This work provides an effective strategy for designing red TADF molecules by managing energy level alignments to facilitate the up‐conversion process and thus enhance exciton harvesting.
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