Ping Lu

Multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with superior color purity and high photoluminescence quantum yields (PLQYs) hold great promise for organic light‐emitting diodes (OLEDs). Nevertheless, the rigid planar structures and intrinsically slow reverse intersystem crossing rates ( k _RISC ) of these materials lead to pronounced aggregation‐caused quenching and significant efficiency roll‐off. Here, we propose a sterically shielded heavy‐atom strategy that simultaneously suppresses detrimental π–π stacking, accelerates k _RISC , and reinforces the rigidity of the conjugated framework to retain narrowband emission. The proof‐of‐concept emitters BN‐FLS, BN‐FLSe, and BN‐FLSSe show the green emission at 508–517 nm with the narrow full width at half maximums (FWHMs) of 25–26 nm in solution. Notably, BN‐FLSSe achieves rapid k _RISC of 4.2 × 10 ⁶ s ⁻¹ , maintains high PLQYs above 95%, and stable emission profiles over 1–30 wt% broad doping range. Non‐sensitized OLEDs based on BN‐FLS, BN‐FLSe, and BN‐FLSSe show pure‐green electroluminescence with CIE _y coordinates exceeding 0.70, high maximum external quantum efficiencies (EQE _max s) of 41.7%, 41.1%, and 38.5%, and well‐suppressed efficiency roll‐offs, maintaining EQEs of 21.9%, 30.9%, and 32.7% at 1000 cd m ⁻² , respectively. Impressively, even at high doping concentration of 30 wt%, these devices retain high EQE _max s of 30.7%–33.1% with virtually unchanged emission spectra.

Multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with superior color purity and high photoluminescence quantum yields (PLQYs) hold great promise for organic light‐emitting diodes (OLEDs). Nevertheless, the rigid planar structures and intrinsically slow reverse intersystem crossing rates ( k _RISC ) of these materials lead to pronounced aggregation‐caused quenching and significant efficiency roll‐off. Here, we propose a sterically shielded heavy‐atom strategy that simultaneously suppresses detrimental π–π stacking, accelerates k _RISC , and reinforces the rigidity of the conjugated framework to retain narrowband emission. The proof‐of‐concept emitters BN‐FLS, BN‐FLSe, and BN‐FLSSe show the green emission at 508–517 nm with the narrow full width at half maximums (FWHMs) of 25–26 nm in solution. Notably, BN‐FLSSe achieves rapid k _RISC of 4.2 × 10 ⁶ s ⁻¹ , maintains high PLQYs above 95%, and stable emission profiles over 1–30 wt% broad doping range. Non‐sensitized OLEDs based on BN‐FLS, BN‐FLSe, and BN‐FLSSe show pure‐green electroluminescence with CIE _y coordinates exceeding 0.70, high maximum external quantum efficiencies (EQE _max s) of 41.7%, 41.1%, and 38.5%, and well‐suppressed efficiency roll‐offs, maintaining EQEs of 21.9%, 30.9%, and 32.7% at 1000 cd m ⁻² , respectively. Impressively, even at high doping concentration of 30 wt%, these devices retain high EQE _max s of 30.7%–33.1% with virtually unchanged emission spectra.

Organic light‐emitting diodes (OLEDs) have made great progress and occupy an important position in flat‐panel display market in the past years. Organic emitters have been developed from the first generation of fluorescent materials to the second generation of phosphorescent materials, and to the new generation of luminogens with the ability to harvest non‐emissive triplets, including triplet–triplet annihilation (TTA) materials, thermally activated delayed fluorescence materials, hot exciton materials, and doublet radical materials. The development of fluorescent materials that emit shortwavelength blue light is especially essential for the future use of OLED displays. Hot exciton material mainly harvests the triplet excitation through high‐lying reverse intersystem crossing (hRISC) process from T _n ( n ≥ 2) to S _m ( m ≥ 1). The fast hRISC process has proved to result in the shortened lifetime of triplet exciton at nanoseconds level and greatly avoid the gathering of triplet excitons. In this respect, hot exciton materials show high potential in solving the equilibrium problem of blue emission, efficient excitation utilization, and low efficiency roll‐off at high brightness. This review systematically summarizes recent advances in hot exciton OLEDs. The fundamental principles regarding molecular design are discussed, and representative reported hot exciton luminogens are summarized and analyzed, along with their structure–property relationships and OLED applications. The review aims to provide valuable insights for the future development of high‐performance and stable blue OLEDs based on this innovative mechanism.

The circularly polarized organic light‐emitting diodes (CP‐OLEDs) are of great significance in advanced optoelectronic applications, as they can directly emit circularly polarized electroluminescence (CPEL). Although various CPEL systems have been realized using special chiral emitters, their practical application is often hindered by complex synthesis and tedious enantiomer separation. Therefore, generating CPEL directly from readily available achiral luminescent materials is highly desirable. Herein, two pairs of chiral materials, ( R / S )‐ mCP‐CN and ( R / S )‐ tmCP‐CN , with excellent thermal stability, high singlet/triplet energy levels, obvious CPL properties, and bipolar carrier transport features are designed and synthesized. By employing them as hosts and achiral multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitter as the guest, the corresponding CP‐OLEDs achieve good electroluminescence dissymmetry factors (g _EL ) of 1.37–2.37 × 10 ⁻³ , small full‐width at half‐maximums of 29–31 nm, and high external quantum efficiencies (EQE) of 34.8%–36.7% with ultra‐low roll‐off (EQEs of 25.1%–25.8% at 5000 cd m ⁻² ). Furthermore, the CP‐OLEDs fabricated with commercially available achiral phosphorescence and conventional donor‐acceptor (D‐A) TADF materials also generate intense g _EL values on the order of 10 ⁻³ , along with outstanding EQEs of 22.8%–38.9%, demonstrating a simple and universal strategy for achieving CPEL using available achiral emitters and significantly extending the scope of CP‐OLEDs.

Sensitizing fluorescent materials enables fast and efficient exciton utilization, providing an effective approach to improving the performance of organic light‐emitting diodes (OLEDs) beyond new material design. However, conventional OLEDs usually adopt amorphous structures, which limit efficient photon output under low driving voltages. In this work, two fabrication methods for sensitization‐based fluorescent OLEDs using crystalline host matrix (CHM) are proposed. By leveraging the high carrier mobility of CHM and the efficient exciton collection of the hot exciton material PyPO, two sensitized crystalline organic light‐emitting diodes (via hot exciton sensitizer type and exciton nanoaggregates type) exhibit excellent electroluminescence, with maximum external quantum efficiencies of 9.12% and 7.03%, respectively. Both OLEDs exhibit fast turn‐on behavior, with rapid increases in luminance and current density under the same driving voltage. This leads to improved photon output and reduced Joule heat loss ratio from series resistance. Integrating sensitization strategies into crystalline materials provides a novel pathway toward low‐power, high‐brightness OLEDs.

Targeted deuterated donor integration boosts PLQY and efficiency, enabling BN-pCzPhD with Φ _PL = 98% and 37.6% EQE in OLEDs.

Wide band gap organic molecule with ultralong room‐temperature phosphorescence (RTP) remains a big challenge in optoelectronic field due to the intrinsic large Stokes shift of phosphorescence relative to fluorescence, and complexity of filling and stabilizing high‐energy triplet excited states. In this work, three organic small molecules, MSPA , BSPA , and TSPA , based on succinimide and triphenylamine groups are designed and synthesized, and deep‐blue RTP with reversible photoactivation properties is successfully realized by physically doping them into polyvinyl alcohol (PVA) matrix. Notably, MSPA ‐doped film exhibits RTP at 440 nm with ultralong lifetime of 1403 ms and phosphorescence quantum yield as high as 14.32%. Theoretical calculations reveal that the efficient intersystem crossing and strong intermolecular hydrogen‐bonding interactions leads to the ultralong RTP in MSPA /PVA doping system. Taking advantages of the wide band gaps, tunable organic afterglow, and reversible photoactivation behaviors of MSPA , BSPA , and TSPA , the amorphous and flexible films are prepared and show potential applications in photoactivated information encryption, advanced anti‐counterfeiting, and multicolored displays through triplet‐to‐singlet Förster energy transfer. This work provides a reliable strategy to realize high‐performance wide band gap RTP materials and further broadening practical applications in organic optoelectronic information.

Wide band gap organic molecule with ultralong room‐temperature phosphorescence (RTP) remains a big challenge in optoelectronic field due to the intrinsic large Stokes shift of phosphorescence relative to fluorescence, and complexity of filling and stabilizing high‐energy triplet excited states. In this work, three organic small molecules, MSPA , BSPA , and TSPA , based on succinimide and triphenylamine groups are designed and synthesized, and deep‐blue RTP with reversible photoactivation properties is successfully realized by physically doping them into polyvinyl alcohol (PVA) matrix. Notably, MSPA ‐doped film exhibits RTP at 440 nm with ultralong lifetime of 1403 ms and phosphorescence quantum yield as high as 14.32%. Theoretical calculations reveal that the efficient intersystem crossing and strong intermolecular hydrogen‐bonding interactions leads to the ultralong RTP in MSPA /PVA doping system. Taking advantages of the wide band gaps, tunable organic afterglow, and reversible photoactivation behaviors of MSPA , BSPA , and TSPA , the amorphous and flexible films are prepared and show potential applications in photoactivated information encryption, advanced anti‐counterfeiting, and multicolored displays through triplet‐to‐singlet Förster energy transfer. This work provides a reliable strategy to realize high‐performance wide band gap RTP materials and further broadening practical applications in organic optoelectronic information.

High-efficiency organic emitters that meet the increasing demand of BT. 2020 for vivid color reproduction are of significant importance for organic light-emitting diodes (OLEDs).

Multiresonance thermally activated delayed fluorescence (MR-TADF) materials, characterized by narrowband emission and high exciton utilization efficiency, have emerged as promising gain media for organic semiconductor lasers. However, achieving low-threshold lasing...