Multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters have attracted considerable interest due to their superiority in high-resolution organic light-emitting diodes (OLEDs), but suffer from severe aggregation-caused quenching and slow reverse intersystem crossing. Herein, a dynamic pendulum strategy is proposed, in which electron donors are tethered to the classic boron-nitrogen MR core (BCzBN) by employing an oxygen atom as a flexible anchoring point. Benefitting from the distinctive oxygen linkage and dynamic swinging behavior, the resultant MR-TADF emitters can access multiple isomeric conformations, thereby simultaneously achieving blue-shifted emission, preserved narrow full width at half maximum, enhanced quenching resistance, and faster spin flipping compared with BCzBN. As a consequence, the corresponding OLEDs achieve bright blue narrowband electroluminescence in an extremely wide doping window of 1-30 wt%, revealing a record-high external quantum efficiency of 30.4% even at 20 wt%. The results clearly highlight the great potential of the dynamic pendulum strategy for efficient blue MR-TADF emitters.

Donor-acceptor (D-A) conjugated polymers are believed to be a promising skeleton for efficient thermally activated delayed fluorescence (TADF). However, it still remains a big challenge to determine the synergistic tuning between the singlet-triplet energy gap (ΔEST) and the oscillator strength (f). Aiming at this object, a polymerization site regulation has been proposed by selecting the same tetramethyl-substituted triphenylamine as the donor and thioxanthone-10,10-dioxide as the acceptor to construct D-A based TADF polymers. Such a design can preserve a small ΔEST of 40–60 meV for all polymers so as to realize a distinct TADF due to the methyl-induced steric locking, while their emission maxima remain almost unchanged. Most importantly, ongoing from 2,7-polymerization to 3,6-polymerization, the photoluminescence quantum yield is found to grow considerably from 20.0

Three topology-varied light emitters m-CzBP, o-2CzBP and 2o-CzBP were obtained, among which m-CzBP was synthesized by substituting carbazole on the meta position of benzophenone, double substituting carbazole on the ortho positions of benzophenone to produce o-2CzBP and coupling two carbazole ortho-positioned benzophenone to result in diploid 2o-CzBP. With the increases of the water contents in the mixture solvents of tetrahydrofuran and water, the emission spectra of m-CzBP and o-2CzBP shows an obviously increased red-shifted emission with the other decreased while 2o-CzBP showing typical aggregation-induced emission without obvious emission peak change. The molecular aggregates will become larger, and the intermolecular interactions will be strengthened. In addition, m-CzBP, o-2CzBP and 2o-CzBP all have twisted structures, and there is a relatively large dihedral angle between benzophenone and carbazole, which helps to break the whole conjugations, so that the highest occupied molecular orbital and lowest unoccupied molecular orbitals are more dispersed, which is beneficial for the intersystem crossing and reverse intersystem transition process. In virtue of its intramolecular interaction, the solid powder of 2o-CzBP obtains highly efficient green thermally activated delayed fluorescence with a relatively high photoluminescent quantum efficiency of 12.62%. In addition, we have developed a series of OLEDs based on the emitting layers of non-doped and doped compounds using o-2CzBP and 2o-CzBP as active luminescent layers and hosts, and the maximum external quantum efficiency of the green phosphorescent OLED device hosted by o-2CzBP is 22.8%. A series of devices with 2o-CzBP as guest shows a maximum external quantum efficiency of 8.2%.

The development of deep blue thermally activated delayed fluorescence (TADF) emitters still remains a big challenge. In this work, four donor-bridge-acceptor type sulfur-containing TADF emitters are developed with carbazole (Cz) derivatives as the donor unit and triphenyltriazine (Trz) as the acceptor moiety. The sulfur atom was used as the bridge to construct Trz-S-Cz and Trz-S-tBuCz, and the sulfone group was employed to construct Trz-SO2-Cz and Trz-SO2-tBuCz. The sp3 sulfur bridge interrupts the conjugation between Cz and Trz groups, leading to totally separated orbital distribution. The electron-deficient sulfone group deepens the LUMO level and produces the redshifted emitting wavelength compared to the sulfur atom containing emitters. The four emitters show blue emission, excellent thermal stability and small LEST values. The optimized OLEDs based on TrZ-S-Cz and Trz-S-tBuCz realize the highest external quantum efficiencies (EQEs) of 22.0 % and 18.2 %, respectively. The sulfone group containing emitters TrZ-SO2-Cz and TrZ-SO2-tBuCz achieve the maximum EQEs of 20.1 % and 19.6 %, respectively. The efficiency roll-offs are relatively small for all these devices. The device based on TrZ-S-Cz exhibits deep blue electroluminescence spectrum with peak at 456 nm and a CIE coordinate of (0.15, 0.14). These results demonstrate that incorporating the sulfur atom is an effective way to construct efficient TADF emitters.

D-O-A organic phosphors showing strong aggregation-induced room-temperature phosphorescence (RTP) have been successfully demonstrated as the ideal matrix-free sensitizers for MR-TADF OLEDs. However, weak emissive ones still remain unexplored according to a habitual thinking that the best sensitizer should be the best emitter. Herein, a poor RTP emitter named RTP-D3 is newly developed based on carbazole as the donor, triazine as the acceptor and oxygen as the bridge. In spite of the extremely low photoluminescence quantum yield, RTP-D3 can sensitize the terminal MR-TADF molecules effectively and universally because of favored π-π and C-H∙∙∙π intermolecular interactions among triazine moieties and thus a balanced charge transport. Consequently, high performance sky-blue, green, yellow and red narrowband electroluminescence is realized together with a state-of-art external quantum efficiency of 22.2% (49.2 cd/A, 55.2 lm/W), 31.5% (105.1 cd/A, 113.9 lm/W), 32.9% (112.4 cd/A, 133.3 lm/W) and 29.7% (55.4 cd/A, 66.9 lm/W) as well as Commission Internationale de l’Eclairage (CIE) coordinates of (0.12, 0.48), (0.26, 0.70), (0.45, 0.54) and (0.61, 0.39), respectively. The exceptional results break a conventional blind spot about RTP sensitizer, highlighting that the less emissive D-O-A organic phosphors are also suitable for the best matrix-free sensitization in MR-TADF OLEDs.

Donor-acceptor type covalent organic frameworks (D-A COFs) have emerged as a promising class of photocatalytic materials due to their highly porous structures and excellent photo charge separation. However, the role of linkage between donor and acceptor in regulating charge transport and reaction selectivity remains not fully elucidated. Inspired by molecular diodes with similar D-A structure and specific rectification character, we designed and synthesized two molecular diode-based COF isomers (PyAm-PhAl-COF and PyAl-PhAm-COF), and systematically investigated their switchable electron transfer and photocatalytic hydrogen evolution. These isomers exhibit pronounced pH-responsive current rectification during photo-induced electron transfer, with the behavior directly driven by imine bond orientation. Specifically, PyAm-PhAl-COF facilitates efficient electron transfer under alkaline conditions, achieving a hydrogen evolution rate 172 times higher than that under acidic conditions. In contrast, PyAl-PhAm-COF displays an opposite trend, with a 25-fold activity enhancement under acidic vs. alkaline environments. This "acid-base switching effect" originates from protonation/deprotonation-induced reversal of the imine bond dipole: the dipole change dynamically regulates the intramolecular electron transport pathway, thereby governing the selective oxidation of different electron donors. These findings not only deepen the understanding of structure-performance relationships in D-A COFs but also provide a new design strategy for developing adaptive smart photocatalytic systems.

A series of donor-oxygen-acceptor (D-O-A)-type polymers have been newly designed and synthesized, where benzophenone, 1,3-bis(phenylmethanone)-phenylene or 1,4-bis(phenylmethanone)-phenylene is selected as the acceptor combined with the acridine donor through an oxygen linkage. The characteristic geometry endows them with obvious phosphorescence at room temperature for both the neat and doped films. Meanwhile, their emission colors can be finely tuned with increasing electron withdrawing ability of the acceptor. As a consequence, the corresponding polymer light-emitting diodes achieve a bright sky-blue, green and yellow electroluminescence peaking at 482, 502 and 547 nm, respectively. The color modification via acceptor engineering clearly highlights the great universality and potential of the D-O-A design for efficient pure organic room-temperature electrophosphorescent polymers.

Donor-acceptor covalent organic frameworks (D-A-COFs) have emerged as promising materials for photocatalytic water splitting owing to their intrinsic electron transfer mechanism. However, their practical applications are still constrained by inefficient charge separation. Herein, we developed a series of ternary COFs by systematically regulating distinct acceptor components to optimize charge separation and transfer in photocatalysis. By employing a sulfone-based ligand as the donor and modulating the molar ratio of the two acceptor ligands, we successfully synthesized five ternary COFs (DS-OHOMe-COF-1 to DS-OHOMe-COF-5). Remarkably, DS-OHOMe-COF-3 exhibited a photocatalytic hydrogen evolution rate of 141.8 mmol g-1 h-1 under visible light irradiation (>= 420 nm) with 1 wt % platinum loading, up to 13.1 times higher than that of binary systems DS-OMe-COF (10.8 mmol g-1 h-1). In addition, the apparent quantum yield (AQY) of DS-OHOMe-COF-3 increased up to 1.33% at 420 nm. Comprehensive characterizations including electrochemical tests, transient absorption spectroscopy, fluorescence decay curves, etc. revealed that the asymmetric ternary COF system significantly optimized the electronic configuration by introducing multiple monomers, thus promoting spatial charge separation and suppressing electron-hole recombination. Density functional theory calculations further demonstrate that the ternary DS-OHOMe-COF-3 exhibits a distinct D-pi-A electronic structure and the lowest energy barrier for efficient charge separation and hydrogen evolution reaction. This work provides insights into enhancing the photocatalytic hydrogen production activity of COFs through the systematic structural engineering of donor and acceptor components.

ABSTRACT With the rapid advancement of wearable electronics and bioelectronics, the construction of flexible energy‐supplying systems that simultaneously integrate high‐efficiency energy conversion, excellent body‐conformability, and mechanical durability has emerged as a critical challenge urgently requiring breakthroughs in the thermoelectric field. Recently, Lei et al. have developed a robust thermoelectric elastomer that simultaneously exhibits a high thermoelectric figure of merit (ZT value), excellent tensile resilience, and low modulus. This innovation overcomes the long‐standing challenge of balancing the “mechanical‐electrical‐thermal” performance of thermoelectric materials, thereby opening up new avenues for the continuous self‐powering and solid‐state cooling of wearable devices.

The development of universal host materials with balanced bipolar transport properties and appropriate energy level alignment for diverse dopant emitters remains highly challenging for high-performance OLEDs. This study presents two bipolar host materials, 3CN-mCBP and 4CN-mCBP, by introducing cyano (CN) groups at the 3- or 4positions of carbazole rings in the well-known hole-transport host mCBP (3,3 '-di(9H-carbazol-9-yl)-1,1 ' biphenyl). Compared to mCBP, the modified hosts exhibit comparable or slightly reduced triplet energy levels, along with deeper HOMO and LUMO energy levels. Charge transport characterization demonstrates enhanced electron injection/transport in the order of 4CN-mCBP > 3CN-mCBP >> mCBP, with hole transport capabilities following the reversed sequence: mCBP > 4CN-mCBP > 3CN-mCBP. In green phosphorescent OLEDs using (ppy)2Ir(acac), the CN-modified hosts achieve superior efficiencies (21.6 % and 19.9 % EQE) versus mCBP (11.8 %), while blue devices with FIrpic show opposite performance trends. For green TADF emitter 4tCzDOXD, all hosts yield comparable efficiencies (15.3-17.9 %). These results highlight the challenges in developing universal host materials for diverse emitter systems.

The contact between inorganic electrodes and organic layers serves as both a charge-carrier conduit and a crucial topological link in organic optoelectronic devices, significantly impacting carrier injection/extraction efficiency and long-term stability. A barrier-free contact for hole injection with thermodynamic stability at the inorganic electrode/organic interface is essential for efficient devices. However, this has not yet been realized between metal electrodes and organic materials with high ionization energy (IE). Here we demonstrate a quantized electrode with surface charge-transfer states formed by chemisorbed ultrathin organic layer on an aluminum surface. This quantized electrode, featuring a new injection mechanism, forms universal ohmic hole contacts with organic semiconductors possessing high IEs up to 6.1 eV, rendering the conventional rule of ohmic hole contact that the work function of the anode must match the IE of the organic semiconductor invalid. The resultant organic light-emitting diode (OLED) achieves ultrahigh luminance at low voltage and extremely low efficiency roll-off. Moreover, the quantized electrode exhibits excellent thermal stability, with a seventeen-fold increase in operational lifetime compared to the reference device. Quantized electrodes will facilitate the development of OLED microdisplays and have potential applications in other advanced semiconductors requiring ohmic hole contact and robust stability.

Chiral organic phosphors with room-temperature phosphorescence (RTP) show a great potential in high-performance circularly polarized organic light-emitting diodes (CP-OLEDs). As a proof of concept, herein, we report a pair of chiral RTP enantiomers (S/R)-CP-RTP-D1 with acridine as the donor (D), triazine as the acceptor (A), oxygen as the bridge, and (S/R)-2-methylbutane as the chiral alkyl chain. It is found that the effective chiral perturbation can endow (S/R)-CP-RTP-D1 with mirror symmetric chiroptical properties, while maintaining the characteristic RTP emission. Consequently, the corresponding doped and non-doped CP-OLEDs based on (S/R)-CP-RTP-D1 achieve obvious circularly polarized electroluminescence (CPEL) signals, revealing promising external quantum efficiencies of 14.9

Pure organic phosphors capable of room-temperature phosphorescence show a great potential in organic light-emitting diodes, while it is limited by the big challenge to realize efficient electroluminescence under electric excitation. Herein, we develop a class of organic phosphors based on acridine as the electron donor, triazine as the electron acceptor and oxygen as the bridge between them. Benefitting from the characteristic donor-oxygen-acceptor geometry, these compounds are found to behave an exciting aggregation-induced organic room-temperature electrophosphorescence, and achieve a record-high external quantum efficiency of 15.8% for non-doped devices. Furthermore, they can sensitize multi-resonant emitters in the absence of any additional wide bandgap host, leading to an effective narrowband emission with a peak external quantum efficiency of 26.4% and a small full-width at half maximum of 26 nm. The results clearly indicate that donor-oxygen-acceptor geometry is a promising strategy to design organic phosphors suitable for organic light-emitting diodes.

Comprehensive Summary Conjugated fused‐ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited‐state relaxation and non‐radiative decay, and further to enhance the luminance efficiency for emissive materials. Herein, we develop a series of donor‐acceptor type thermally activated delayed fluorescence (TADF) emitters by introducing fused‐ring 5 H ‐benzofuro[3,2‐ c ]carbazole (32BFCz) as electron donating unit. Through optimizing the numbers and structure of donor and acceptor moieties, three compounds named 32BFCzA, m CF 3 BFCzOXD and dCF 3 BFCzOXD are designed, which are composed by mono‐32BFCz/trifluoromethylpicolinonitrile, penta ‐BFCz/3‐(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene and penta ‐32BFCz/3,5‐bis(trifluoromethyl)phenyl)‐1,3,4‐oxadiazol‐2‐yl)benzene as donor/acceptor groups, respectively. They all exhibited green emission with peak value ranging from 532 to 540 nm. Through rationally tuning the donor/acceptor properties to reduce the distance between positive and negative charges, the ground state dipole moments decline from 8.93, 6.18 to 5.30 Debye, which further induced sequentially reduced singlet‐triplet energy splits (Δ E ST s), increased photoluminescence quantum yields (PLQYs), enhanced reverse intersystem crossing rate ( k RISC s) and diminished delayed fluorescence lifetime from 32BFCzA, m CF 3 BFCzOXD to dCF 3 BFCzOXD. Therefore, gradually increased external quantum efficiency (EQE) is accordingly achieved when employing them as emitters for TADF OLEDs. dCF 3 BFCzOXD with the mostly optimized donor/acceptor structures demonstrates the highest efficiency with maximum EQE to 21.4%. Our work provides guidelines on the design of high‐efficiency D‐A type TADF materials.

Different from spiro-blocking, frontier molecular orbital engineering has been proposed to develop AT-spiro-DMACF, which shows interesting aggregation-induced delayed fluorescence (AIDF) for non-doped OLEDs.

Introducing cyano units to improve the molecular polarity of the host material greatly enhances the device efficiency for TADF OLEDs.

Two orange-red TADF emitters, employing dicyanopyrazino phenanthrene as the acceptor and 3,6-disubstituted carbazole as the donor, were developed for use as high-efficiency solution-processed OLEDs with a low efficiency roll-off.

A rigid π-conjugated and electron-deficient moiety, dipyrido[3,2-a:2′,3′-c]phenazine (DPPZ), was employed as the electron acceptor for thermally activated delayed fluorescence (TADF) emitters with a donor–acceptor structure. Two TADF emitters, DCz-DPPZ and DDPhCz-DPPZ, were prepared by adopting carbazole derivatives as the donor and DPPZ as the acceptor. Compared to DCz-DPPZ without substituents at the carbazole group, DDPhCz-DPPZ showed a narrower energy gap, a longer emission wavelength, and a higher photoluminescence quantum efficiency. The TADF organic light-emitting diodes based on DDPhCz-DPPZ exhibited a higher quantum efficiency of 12.4% than 4.6% of devices based on DCz-DPPZ. These results demonstrate that DPPZ is a suitable acceptor for constructing D–A type TADF emitters.

Three novel emitters with dual emitting cores, namely 3,3 & PRIME;,5,5 & PRIME;-tetra(triphenylamine-4-yl)-[1,1 & PRIME;-biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DDTPAIPN), 3,3 & PRIME;-di(triphenylamine-4-yl)-5,5 & PRIME;-di(3,5-(9,9 & PRIME;-dicarbazolyl)phenyl)-[1,1 & PRIME;- biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DTPAmCPIPN), and 3,3 & PRIME;,5,5 & PRIME;-tetra(3,5-(9,9 & PRIME;-dicarbazolyl)phenyl)-[1,1 & PRIME;- biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DDmCPIPN) are designed and synthesized by coupling their respective single core emitters. Compared with their single core counterparts, the three novel compounds exhibit significantly improved thermal stability, absorption coefficients, and photoluminescence efficiencies in neat films. Photophysical measurements show that these three emitters exhibit both aggregation-induced emission and thermally activated delayed fluorescence properties, which is beneficial for non-doped organic light-emitting diodes (OLEDs). The new compounds show relatively balanced charge carrier transport abilities as revealed by unipolar devices. The solution-and evaporation-processed doped and non-doped OLEDs made from these three luminophores achieve excellent electroluminescence (EL) performances. The peak current, power, and external quantum efficiencies of a DTPAmCPIPN-based solution-processed doped device reach 59.2 cd A(-1), 61.3 lm W-1, and 17.2%, respectively, with an emission peak at 548 nm. The evaporation-processed doped device based on DTPAmCPIPN exhibits maximum EL efficiencies of up to 63.7 cd A(-1), 61.1 lm W-1, and 19.2%. Moreover, the non-doped OLEDs also possess superior EL efficiencies with extremely small efficiency roll-offs. The molecular design strategy in this work is demonstrated to be effective in developing new emitters for efficient and stable OLEDs.

Possessing the reverse intersystem crossing (RISC) process, exciplex system has vast potential to enhance the efficiency of the white organic light-emitting diodes (WOLEDs). Nevertheless, general structures of the emitting layer always employ triple-doping in a long range (20?30 nm) which is complicated on fabrication progress. In this paper, based on the interfacial exciplex co-host, a flexible and simplified structure design is proposed to realize both warm and cold phosphorescent WOLEDs. In the two devices, with strategically locating the ultrathin orange phosphorescent emitting layers at two sides of the blue phosphorescent emitting layer (2 nm), respectively, multiple energy transfer channels are created to carry out highly efficient exciton utilization. Owing to the different energy transfer mechanisms, different organic emission ratios are obtained in two WOLEDs. The cold WOLEDs exhibited superior maximum external quantum efficiency (EQE), current efficiency (CE) and power efficiency (PE) of 28.37%, 72.17 cd A-1 and 87.17 lm W- 1, respectively. Also, the warm WOLEDs showed high values as EQE of 23.80%, CE of 67.70 cd A-1 and PE of 81.10 lm W-1. Furthermore, both the devices presented rather stable color output in the luminance range from 2000 cd m- 2 to 10000 cd m.-2