Dongdong Zhang

Organic scintillators have experienced notable advancements in performance, garnering considerable attention and demonstrating promising potential for diverse applications. However, an ideal scintillator requires efficient radiation absorption, rapid radiative decay, excellent stability, and a high light yield; it still remains challenging to simultaneously fulfill these criteria for a single organic material. Here, we propose to fabricate energy transfer cascade organic scintillators based on the TADF‐sensitized fluorescence (TSF) mechanism, in which the functions of x‐ray energy absorption, triplet exciton up‐conversion, and singlet exciton radiative transition are decoupled by three components cooperating to break through intrinsic shackles. As a result, a highlight output of 28.90 times that of anthracene crystal, a record detection limit as low as 17.69 nGy _air s ⁻¹ , and an imaging resolution of 23.3 lp mm ⁻¹ were achieved. This work validates the universality and potential of the TSF mechanism to boost the performance of organic scintillators and is expected to advance the rapid development of organic scintillators.

Organic scintillators have experienced notable advancements in performance, garnering considerable attention and demonstrating promising potential for diverse applications. However, an ideal scintillator requires efficient radiation absorption, rapid radiative decay, excellent stability, and a high light yield; it still remains challenging to simultaneously fulfill these criteria for a single organic material. Here, we propose to fabricate energy transfer cascade organic scintillators based on the TADF‐sensitized fluorescence (TSF) mechanism, in which the functions of x‐ray energy absorption, triplet exciton up‐conversion, and singlet exciton radiative transition are decoupled by three components cooperating to break through intrinsic shackles. As a result, a highlight output of 28.90 times that of anthracene crystal, a record detection limit as low as 17.69 nGy _air s ⁻¹ , and an imaging resolution of 23.3 lp mm ⁻¹ were achieved. This work validates the universality and potential of the TSF mechanism to boost the performance of organic scintillators and is expected to advance the rapid development of organic scintillators.

The strategic integration of thermally activated delayed fluorescence (TADF) sensitizers has emerged as a critical approach for triplet recycling in organic light‐emitting diodes (OLEDs) with multiple resonance (MR) emitters. However, conventional single‐sensitizer systems are frequently limited by slow exciton utilization and thus severe efficiency roll‐off. This study develops a multi‐sensitization strategy through the integrated design of a novel sensitizing host and parallel energy‐transfer pathways to accelerate exciton utilization. The novel D‐ meta ‐π‐A host exhibits a reverse intersystem crossing rate of 3.18 × 10 ⁶ s ⁻¹ and a radiative decay rate of 1.94 × 10 ⁷ s ⁻¹ , together with balanced charge transport and blue‐shifted photoluminescence in the neat film. Its photophysical behavior is consistent with contributions from both intra‐ and intermolecular charge‐transfer (CT) states. The optimized device demonstrates remarkable electroluminescence performance with a maximum external quantum efficiency (EQE) of 37.1%, a record‐high EQE of 32.4% at 5,000 cd m ⁻² , a turn‐on voltage (at 1 cd m ⁻² ) of 2.4 V, and a maximum power efficiency (PE) of 58.0 lm W ⁻¹ , exhibiting deep‐blue emission, ultra‐low power consumption, and suppressed efficiency roll‐off. This work provides a viable design paradigm for high‐performance MR‐OLEDs through synergistic exciton management and sensitizer engineering.

The strategic integration of thermally activated delayed fluorescence (TADF) sensitizers has emerged as a critical approach for triplet recycling in organic light‐emitting diodes (OLEDs) with multiple resonance (MR) emitters. However, conventional single‐sensitizer systems are frequently limited by slow exciton utilization and thus severe efficiency roll‐off. This study develops a multi‐sensitization strategy through the integrated design of a novel sensitizing host and parallel energy‐transfer pathways to accelerate exciton utilization. The novel D‐ meta ‐π‐A host exhibits a reverse intersystem crossing rate of 3.18 × 10 ⁶ s ⁻¹ and a radiative decay rate of 1.94 × 10 ⁷ s ⁻¹ , together with balanced charge transport and blue‐shifted photoluminescence in the neat film. Its photophysical behavior is consistent with contributions from both intra‐ and intermolecular charge‐transfer (CT) states. The optimized device demonstrates remarkable electroluminescence performance with a maximum external quantum efficiency (EQE) of 37.1%, a record‐high EQE of 32.4% at 5,000 cd m ⁻² , a turn‐on voltage (at 1 cd m ⁻² ) of 2.4 V, and a maximum power efficiency (PE) of 58.0 lm W ⁻¹ , exhibiting deep‐blue emission, ultra‐low power consumption, and suppressed efficiency roll‐off. This work provides a viable design paradigm for high‐performance MR‐OLEDs through synergistic exciton management and sensitizer engineering.

In this study, we report a spatial planarization strategy for asymmetric Ir(III) complexes that simultaneously improves exciton stability and optical outcoupling in blue OLEDs. By incorporating bulky tert ‐butylcarbazole (tBuCz) units into tridentate N‐heterocyclic carbene ligands, the molecular geometry is sterically confined into a more coplanar and anisotropic configuration. This structural planarization increases exciton binding energy and shortens the radiative lifetime, thereby stabilizing bound excitons against thermally activated dissociation while accelerating radiative exciton consumption. At the same time, the enhanced geometric anisotropy induces a highly horizontal emitting dipole orientation (EDO) of approximately 95%, enabling efficient intrinsic light extraction. Beyond its role as an emitter, the planarized Ir(III) complex further has a cooperative alignment effect in hyper‐OLED architectures. This structural and electrostatic templating effect transfers molecular alignment to the terminal multiple‐resonance TADF emitter v ‐DABNA, leading to secondary dipole ordering with an EDO of 98%. As a result, the optimized blue hyper‐OLED achieves ultra‐narrow emission at 470 nm with a full width at half maximum of 22 nm, a maximum external quantum efficiency of 36.9%, and an operational lifetime (LT ₅₀ , time to 50% initial luminance) of 446 h at 1000 cd m ⁻² . These results establish spatial planarization as a powerful molecular design principle for coupling exciton stabilization, dipole orientation control, and interfacial alignment transfer, providing a general strategy for efficient and stable blue OLEDs.

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters are a research focus for organic light‐emitting diodes (OLEDs) targeting ultra‐high‐definition displays. Expanding the multi‐resonance plane through multi‐boron structures enables emission color tuning and spectral narrowing, which rigid indolocarbazole moieties could further reinforce. However, excessive expansion of conjugated aromatic planes leads to severe aggregation‐caused quenching (ACQ). Herein, we combined the spirofluorene‐based multi‐resonance skeleton with indolocarbazoles as the bridging unit to construct a double‐boron architecture, aiming to utilize the three‐dimensional spatial rigidity of spirofluorene while suppressing intermolecular interactions in aggregated states. Three isomeric emitters were thereby obtained, with emission maxima at 524–565 nm. All emitters exhibit full widths at half‐maximum below 20 nm, with the narrowest being 17 nm, and these emitters maintain narrow‐band emission even at a high doping concentration of 6 wt%, where film spectral broadening is limited to within 3 nm. OLEDs based on these emitters display narrow bandwidths of 22–26 nm, the highest maximum EQE of 36.2%, and low efficiency roll‐off, corresponding to a high EQE of up to 30.2% even under ultra‐high luminance of 5 × 10 ⁴ cd m ⁻² . This work confirms the feasibility of spirofluorene‐modified multi‐boron large‐plane multi‐resonance emitters and provides a reliable molecular design strategy for narrowband OLEDs.

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters are a research focus for organic light‐emitting diodes (OLEDs) targeting ultra‐high‐definition displays. Expanding the multi‐resonance plane through multi‐boron structures enables emission color tuning and spectral narrowing, which rigid indolocarbazole moieties could further reinforce. However, excessive expansion of conjugated aromatic planes leads to severe aggregation‐caused quenching (ACQ). Herein, we combined the spirofluorene‐based multi‐resonance skeleton with indolocarbazoles as the bridging unit to construct a double‐boron architecture, aiming to utilize the three‐dimensional spatial rigidity of spirofluorene while suppressing intermolecular interactions in aggregated states. Three isomeric emitters were thereby obtained, with emission maxima at 524–565 nm. All emitters exhibit full widths at half‐maximum below 20 nm, with the narrowest being 17 nm, and these emitters maintain narrow‐band emission even at a high doping concentration of 6 wt%, where film spectral broadening is limited to within 3 nm. OLEDs based on these emitters display narrow bandwidths of 22–26 nm, the highest maximum EQE of 36.2%, and low efficiency roll‐off, corresponding to a high EQE of up to 30.2% even under ultra‐high luminance of 5 × 10 ⁴ cd m ⁻² . This work confirms the feasibility of spirofluorene‐modified multi‐boron large‐plane multi‐resonance emitters and provides a reliable molecular design strategy for narrowband OLEDs.

Indolocarbazole‐bridged double‐boron multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials enable precise modulation of emission colors while retaining ultra‐narrowband characteristics in organic light‐emitting diodes (OLEDs). Herein, we first introduce indolo[2,3‐c]carbazole (23cIC) into the design of MR‐TADF emitters and develop an electronically and sterically controlled multi‐site borylation strategy. This strategy affords the electronically favored exo‐configuration for Tbu‐exo, which exhibits narrowband green emission at 524 nm with a full‐width at half‐maximum (FWHM) of 20 nm, while yielding the steric hindrance‐guided endo‐configuration for Ad‐tph‐endo exhibiting by yellow emission at 566 nm with a FWHM of 25 nm. Notably, the endo‐configuration gives rise to ( P / M )‐Ad‐tph‐endo, which exhibits significant chiral luminescence properties. Vacuum‐deposited OLEDs based on Tbu‐exo and Ad‐tph‐endo exhibit emission peaks at 530 nm (FWHM = 27 nm) and 568 nm (FWHM = 33 nm), respectively, both achieving external quantum efficiencies (EQE) exceeding 30%. Furthermore, we fabricated solution‐processed top‐emitting OLEDs based on Tbu‐exo for the first time, which realize ultra‐narrow pure‐green emission with CIE coordinates of (0.21, 0.75)—closely approaching the BT.2020 green standard—and a record‐high current efficiency of 200.9 cd A ⁻¹ .