π-Conjugated, narrow band gap copolymers containing pyridal[2,1,3]thiadiazole (PT) were synthesized via starting materials that prevent random incorporation of the PT heterocycles relative to the backbone vector. Two regioregular structures could be obtained: in one the PTs are oriented in the same direction, and in the other the orientation of the PTs alternates every other repeat unit. Compared to their regiorandom counterparts, the regioregular polymers exhibit a 2 orders of magnitude increase of the hole mobilites, from 0.005 to 0.6 cm(2) V(-1) s(-1), as determined by field-effect transistor measurements.

Most thermally activated delayed fluorescence (TADF) emitters have to be doped in the host for fabricating efficient organic light-emitting diodes (OLEDs) and always suffer from quick efficiency roll-off at high brightness, which severely affect their commercial application in display and lighting fields. In the work, a series of the polymers are synthesized by copolymerization of two carbazole monomers and one acridine derivative monomer containing benzophenone acceptor group. The obtained polymers therefore possess a conjugated backbone with carbazole/acridine moieties and benzophenone pendant to form the twisted donor/acceptor structure. Consequently, the TADF features inherited from the acridine derivative are maintained and improved by managing the content of acridine derivative monomer in the polymers. Solution-processed OLEDs obtained from using neat polymer films exhibit comparable performance with organic TADF small molecules, achieving a maximum external quantum efficiency (EQE) of 18.1% and a very slow roll-off with EQE of 17.8% at the luminance of 1000 cd m −2 .

Scheme 1. Polymer Structures a a LKey: (a) General D-A type conjugated polymers, in which donors and acceptors are connected to each other in the backbone, resulting in large overlap between the HOMO and LUMO. (b) Designed conjugated polymers in which only donors are fixed in the backbone and acceptors are grafted in the side-chain. The HOMO and LUMO are sufficiently spatially separated to obtain a small ΔE ST . (c) Polymer structures of PAPCC and PAPTC. Note pubs.acs.org/Macromolecules

Emission thermal quenching is commonly observed in quasi-2D perovskite emitters, which causes the severe drop in luminescence efficiency for the quasi-2D perovskite light-emitting diodes (PeLEDs) during practical operations. However, this issue is often neglected and rarely studied, and the root cause of the thermal quenching has not been completely revealed now. Here, we develop a passivation strategy via the 2,7-dibromo-9,9-bis (3′-diethoxylphosphorylpropyl)-fluorene to investigate and suppress the thermal quenching. The agent can effectively passivate coordination-unsaturated Pb2+ defects of both surface and bulk of the film without affecting the perovskite crystallization, which helps to more truly demonstrate the important role of defects in thermal quenching. And our results reveal the root cause that the quenching will be strengthened by the defect-promoted exciton-phonon coupling. Ultimately, the PeLEDs with defect passivation achieve an improved external quantum efficiency (EQE) over 22% and doubled operation lifetime at room temperature, and can maintain about 85% of the initial EQE at 85 °C, much higher than 17% of the control device. These findings provide an important basis for fabricating practical PeLEDs for lighting and displays.

Three new solution-processable platinum(II) polyyne polymers containing zinc(II) porphyrinate chromophores P1, P2, and P3 and their corresponding dinuclear model complexes were synthesized via the CuI-catalyzed dehydrohalogenation reaction of the platinum(II) chloride precursor and each of the respective bis(ethynyl)-zinc(porphyrin) metalloligands. The thermal, photophysical (absorption, excitation and emission spectra), electrochemical, and photovoltaic properties of P1–P3 were investigated. These results are also correlated by time-dependent density functional theory (TDDFT) calculations. The computations corroborate the presence of moderate conjugation in the π-systems, somewhat more accentuated for P3 where more favorable dihedral angles between the porphyrin and thiophene rings are noted. Moreover, the computed excited states are predicted to be π–π* in nature with some charge transfer components from the trans-[−CCPt(L)2CC−] n unit to the porphyrin rings. The optical bandgaps range from 1.93 to 2.02 eV for P1–P3. Intense π–π*-localized fluorescence emissions typical of the Q-bands of the polymers were observed. The effect of thiophene ring along the polymer chain on the extent of π-conjugation, luminescent and photovoltaic properties of these metalated materials was also examined. Bulk heterojunction solar cells using these metallopolymers as an electron donor blended with a methanofullerene electron acceptor were studied. In one case, the metallopolymer P3 showed a power conversion efficiency of 1.04% with the open-circuit voltage of 0.77 V, short-circuit current density of 3.42 mA cm–2 and fill factor of 0.39 under illumination of an AM 1.5 solar cell simulator.

Efficient white and orange emissions have been achieved in doped OLEDs using TADF conjugated polymers with a backbone-donor/pendant-acceptor architecture.

Polymerization could be a feasible method to overcome the rigid structure induced self-quenching effect in conventional thermally activated delayed fluorescence (TADF) emitters. Despite steady progress in TADF polymer research, developing an efficient red TADF polymer still remains a great challenge because of the large non-radiative internal conversion rate governed by the energy gap law. Herein, a novel strategy for constructing a red TADF conjugated polymer is presented by means of embedding quinoxaline-6,7-dicarbonitrile (QC) as an acceptor into a polycarbazole (PCz) backbone and attaching donor 9,10-dihydroacridine (A) as a pendant. The obtained polymers PCzAQCx with the appropriate molar content of the AQC unit (x ≥ 0.5) exhibit efficient TADF features with a dominant emissive peak at 627−661 nm and a photoluminescence quantum yield of up to 76% in neat film. The non-doped electroluminescent devices with the poly mers produce red emissions with a maximum external quantum efficiency (EQE) of up to 12.5% and the emission peak at 620 nm, which represents state-of-the-art performance for solution-processed devices based on red TADF polymers. Furthermore, combined with a blue TADF emitter, the bright white devices with tunable spectra cover the whole visible-near infrared range from 400 to 900 nm and a record-high EQE of up to 22.4% is achievable.

Non-doped OLEDs employing TADF conjugated polymers exhibit excellent electroluminescent performances.