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In this work, we propose pure hydrocarbon materials as universal hosts for high-efficiency red, green and blue phosphorescent organic light-emitting diodes.

Metal halide perovskite semiconductors have demonstrated remarkable potentials in solution‐processed blue light‐emitting diodes (LEDs). However, the unsatisfied efficiency and spectral stability responsible for trap‐mediated non‐radiative losses and halide phase segregation remain the primary unsolved challenges for blue perovskite LEDs. In this study, it is reported that a fluorene‐based π‐conjugated cationic polymer can be blended with the perovskite semiconductor to control film formation and optoelectronic properties. As a result, sky‐blue and true‐blue perovskite LEDs with Commission Internationale de l'Eclairage coordinates of (0.08, 0.22) and (0.12, 0.13) at the record external quantum efficiencies of 11.2% and 8.0% were achieved. In addition, the mixed halide perovskites with the conjugated cationic polymer exhibit excellent spectral stability under external bias. This result illustrates that π‐conjugated cationic polymers have a great potential to realize efficient blue mixed‐halide perovskite LEDs with stable electroluminescence.

Multi-layer p-stacked emitters based on spatially confined donor/acceptor/donor (D/A/D) patterns have been developed to achieve high-efficiency thermally activated delayed fluorescence (TADF). In this case, dual donor moieties and a single acceptor moiety are introduced to form two threedimensional (3D) emitters, DM-BD1 and DM-BD2, which rely on spatial charge transfer (CT). Owing to the enforced face-to-face D/A/D pattern, effective CT interactions are realized, which lead to high photoluminescence quantum yields (PLQYs) of 94.2 % and 92.8 % for the two molecules, respectively. The resulting emitters exhibit small singlet-triplet energy splitting (DE ST) and fast reverse intersystem crossing (RISC) processes. Maximum external quantum efficiencies (EQEs) of 28.0 % and 26.6 % were realized for devices based on DM-BD1 and DM-BD2, respectively, which are higher than those of their D/A-type analogues.

Organic semiconductors can be designed and constructed in π‐stacked structures instead of the conventional π‐conjugated structures. Through‐space interaction (TSI) occurs in π‐stacked optoelectronic materials. Thus, unlike electronic coupling along the conjugated chain, the functional groups can stack closely to facilitate spatial electron communication. Using π‐stacked motifs, chemists and materials scientists can find new ways for constructing materials with aggregation‐induced emission (AIE), thermally activated delayed fluorescence (TADF), circularly polarized luminescence (CPL), and room‐temperature phosphorescence (RTP), as well as enhanced molecular conductance. Organic optoelectronic devices based on π‐stacked molecules have exhibited very promising performance, with some of them exceeding π‐conjugated analogues. Recently, reports on various organic π‐stacked structures have grown rapidly, prompting this review. Representative molecular scaffolds and newly developed π‐stacked systems could stimulate more attention on through‐space charge transfer the well‐known through‐bond charge transfer. Finally, the opportunities and challenges for utilizing and improving particular materials are discussed. The previous achievements and upcoming prospects may provide new insights into the theory, materials, and devices in the field of organic semiconductors.

Harvesting the narrow bandgap excitons of charge‐transfer (CT) complexes for the achievement of near‐infrared (NIR) emission has attracted intensive attention for its fundamental importance and practical application. Herein, the triphenylene (TP)‐2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) CT organic complex is designed and fabricated via the supramolecular self‐assembly process, which demonstrates the NIR emission with a maximum peak of 770 nm and a photoluminescence quantum yield (PLQY) of 5.4%. The segregated stacking mode of TP‐F4TCNQ CT complex based on the multiple types of intermolecular interaction has a low CT degree of 0.00103 and a small counter pitch angle of 40° between F4TCNQ and TP molecules, which breaks the forbidden electronic transitions of CT state, resulting in the effective NIR emission. Acting as the promising candidates for the active optical waveguide in the NIR region beyond 760 nm, the self‐assembled TP‐F4TCNQ single‐crystalline organic microwires display an ultralow optical‐loss coefficient of 0.060 dB µm−1. This work holds considerable insights for the exploration of novel NIR‐emissive organic materials via an universal “cocrystal engineering” strategy.

A multiple resonance thermally activated delayed fluorescence (MR‐TADF) molecule with a fused, planar architecture tends to aggregate at high doping ratios, resulting in broad full width at half maximum (FWHM), redshifting electroluminescence peaks, and low device efficiency. Herein, we propose a mono‐substituted design strategy by introducing spiro‐9,9′‐bifluorene (SBF) units with different substituted sites into the MR‐TADF system for the first time. As a classic steric group, SBF can hinder interchromophore interactions, leading to high device efficiency (32.2–35.9 %) and narrow‐band emission (≈27 nm). Particularly, the shield‐like molecule, SF1BN, seldom exhibits a broadened FWHM as the doping ratio rises, which differs from the C3‐substituted isomer and unhindered parent emitter. These results manifest an effective method for constructing highly efficient MR‐TADF emitters through a spiro strategy and elucidate the feasibility for steric modulation of the spiro structure in π‐framework.