Rong-Huei Yi

A novel double-boron-containing multiple resonance paradigm featuring a unique para-B-π-B′/meta-N-π-N molecular pattern is proposed. BNB′-1 achieves an emission at 540 nm with a narrow full width at half-maximum of 24.5 nm/0.098 eV, an impressive photoluminescence quantum yield, and excellent organic solubility, thus affording state-of-the-art solution- and vacuum-processed devices with maximum external quantum efficiencies of 36.2% and 40.3%, respectively.

Abstract

Multiple resonance (MR)-type thermally activated delayed fluorescence (TADF) emitters have promising prospects for high-color-purity organic light-emitting diodes (OLEDs), but they are seldom attempted in the fabrication of solution-processed devices. In addition, another issue with MR-TADF emitters is that their heteroatom patterns are very limited, hampering their diversity. Herein, a novel double boron (B)-containing MR-TADF paradigm that merges an unembedded organoboron unit and a B-embedded π-fused MR framework into one system, furnishing a unique para-B-π-B′/meta-N (nitrogen)-π-N molecular pattern is proposed. Based on this, a proof-of-concept molecule, BNB′-1, is developed, simultaneously achieving a bright sharp emission peaking at 540 nm with a full width at half maximum (FWHM) of only 24.5 nm/98 meV, a nearly unity photoluminescence quantum yield and excellent organic solubility. A solution-processed OLED using BNB′-1 emitter delivers an impressive external quantum efficiency (EQE) as high as 36.2% with an emissive FWHM of only 30.0 nm/0.13 eV at ≈540 nm; both parameters set new records among the ever-reported solution-processed MR-OLEDs. Moreover, BNB′-1 also obtains a superhigh EQE of 40.3% in vacuum-processed OLEDs, surpassing all MR-OLEDs in the similar emission region. This work provides an interesting solution to develop high-performance solution-processable MR-TADF emitters with diverse heteroatom patterns.

To guide the pathway toward the flourishing development of high-performance organic electroluminescence devices, the recent progress of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials is summarized with fast RISC rate constant (> 10⁵ s⁻¹) from the perspective of molecular design, optoelectronic properties, and device performance of organic light-emitting diodes. Furthermore, the challenges and future prospects of MR-TADF materials are discussed comprehensively.

Abstract

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have drawn considerable attention because of their remarkable optoelectronic properties of high emission efficiency and narrow emission profile, and represent an active subject of cutting-edge research in the organic electroluminescence (EL). However, the slow reverse intersystem crossing (RISC) rate of MR-TADF emitter caused by the large energy gap (ΔE _ST) and small spin-orbit coupling (SOC) matrix elements between the singlet and triplet excited states limits their further development in organic EL devices. Currently, innovative molecular design strategies have been developed including heavy atom integration, π-extended MR framework and metal perturbation, and so on to improve the RISC process of MR-TADF emitters for high-performance EL devices. Here, an overview is presented on the recent progress of MR-TADF emitters with fast RISC rate ( > 10⁻⁵ s⁻¹), with particular attention to the molecular design, optoelectronic properties, and device performance of organic light-emitting diodes (OLEDs), which intends to systematize the knowledge in this subject for the thriving development of highly efficient MR-TADF emitters. Finally, the challenges and future prospects of MR-TADF materials are discussed comprehensively.

Novel structured hybrid perovskite/organic tandem white LED (POTWLED) by integrating a 2,8-bis(diphenylphosphoryl)dibenzo[b,d] thiophene passivated bottom blue perovskite light-emitting diode unit and a top organic/(orange + red) organic light-emitting diode unit is developed, which promotes the fabrication of high-performance three-color POTWLEDs with a maximum external quantum efficiency of 23.9% with a corresponding color temperature of 2522 K.

Abstract

Perovskite light-emitting diodes (PeLEDs) have shown great potential for low-cost display and lighting technologies, and all-inorganic blue PeLEDs are recognized as a promising substitute for blue fluorescent/phosphorescent organic light-emitting diodes (OLEDs) owing to their superior color purity and great stability potential. However, confined by the solution fabrication process, depositing multi-layered white PeLEDs remains a challenge. Here, a newly designed hybrid perovskite/organic tandem white LED (POTWLED), integrated with a bottom blue PeLED unit and a top orange/(orange + red) OLED unit, to prevent damage to the underlying perovskite layer caused by the deposition of the top emitting layers, is reported. To optimize the performance of POTWLEDs, a conductive passivator of 2,8-bis(diphenylphosphoryl)dibenzo[b,d] thiophene, with a strong surface binding group of P═O, is introduced to passivate perovskite defects, which promotes a maximum external quantum efficiency (EQE) of 17.3% for blue PeLEDs with an emission peak at 488 nm. As a result, based on the optimized blue PeLED units, a maximum EQE of 23.9% with a low color temperature of 2522 K is obtained for POTWLEDs, which is the highest efficiency for perovskite-based WLEDs, illustrating the great potential of the hybrid tandem device in fabricating high-performance perovskite-based WLEDs.

Herein, an organic small molecule with well-defined molecular structure and strong aggregation-induced emission (AIE) activity is synthesized. This molecule can self-assemble into nanoparticle (NM-7) acting as not only adjuvant but also carrier to capture model antigen ovalbumin to form nanovaccine, which can effectively deliver and chronically release antigens and induce effective antigen cross-presentation in draining lymph nodes. Notably, NM-7/ovalbumin (OVA) cancer nanovaccine induces robust tumor-specific CD8⁺ T-cell responses with greatly reduced cell exhaustion. Accordingly, NM-7/OVA cancer nanovaccine shows potent efficacy in both prevention and therapeutic tumor models, and produces an impressive synergistic therapeutic effect when combined with immune checkpoint blockade therapy.

Abstract

Cancer nanovaccine is a promising therapeutic strategy; however, the complicated composition and ambiguous structure of cancer nanovaccines hinder their clinical application. Thus, developing minimalist nanovaccine with simple structural molecule and potent immunostimulatory function is with great value. Herein, an organic small molecule with well-defined molecular structure and strong aggregation-induced emission (AIE) activity is synthesized. This molecule can self-assemble into nanoparticle (NM-7) acting as not only adjuvant but also carrier to capture model antigen ovalbumin to form nanovaccine, which can effectively deliver and chronically release antigens and induce effective antigen cross-presentation in draining lymph nodes. Additionally, the photophysical property of AIE molecule facilitates the determination of in vivo tissue distribution of NM-7. Notably, NM-7/ovalbumin (OVA) nanovaccine induces robust tumor-specific CD8⁺ T-cell responses with greatly reduced cell exhaustion. Accordingly, NM-7/OVA nanovaccine shows potent efficacy in both prevention and therapeutic tumor models, and produces an impressive synergistic therapeutic effect when combined with immune checkpoint blockade (ICB) therapy. Therefore, AIE nanomaterial NM-7 with simple synthesis, well-defined molecular structure and self-adjuvanted function provides a new reference and general strategy for cancer vaccine development.

The non-doped organic light-emitting diode based on PPITPh exhibits an exceptionally high EQE of 11.83% with a CIE coordinate of (0.15, 0.07). The EQE still maintains 10.17% at the brightness of 1000 cd m^-2, and even at a brightness as high as 10 000 cd m⁻², an EQE of 7.5% is still remained.

Abstract

The pursuit for efficient deep blue material is an ever-increasing issue in organic optoelectronics field. It is a long-standing challenge to achieve high external quantum efficiency (EQE) exceed 10% at brightness of 1000 cd m⁻² with a Commission International de L'Eclairage (CIE_y) <0.08 in non-doped organic light-emitting diodes (OLEDs). Herein, this study reports a deep blue luminogen, PPITPh, by bonding phenanthro[9,10-d]imidazole moiety with m-terphenyl group via benzene bridge. The non-doped OLED based on PPITPh exhibits an exceptionally high EQE of 11.83% with a CIE coordinate of (0.15, 0.07). The EQE still maintains 10.17% at the brightness of 1000 cd m⁻², and even at a brightness as high as 10000 cd m⁻², an EQE of 7.5% is still remained, representing the record-high result among non-doped deep-blue OLEDs at 1000 cd m⁻². The unprecedented device performance is attributed to the reversed intersystem crossing process through hot exciton mechanism. Besides, the maximum EQE of orange phosphorescent OLED with PPITPh as host is 32.02%, and remains 31.17% at the brightness of 1000 cd m⁻². Such minimal efficiency roll-off demonstrates that PPITPh is also an excellent phosphorescent host material. The result offers a new design strategy for the enrichment of high-efficiency deep blue luminogen.

Publication date: 1 September 2023

Source: Chemical Engineering Journal, Volume 471

Author(s): Jiawei He, Yulin Xu, Sai Luo, Jingsheng Miao, Xiaosong Cao, Yang Zou

Publication date: 1 September 2023

Source: Chemical Engineering Journal, Volume 471

Author(s): Lang Qu, Hui Xiao, Bao Zhang, Qingping Yang, Jintong Song, Xiangge Zhou, Zong-Xiang Xu, Haifeng Xiang

A series of imidazole-based thermally activated delayed fluorescent emitters have been synthesized and characterized. The electrochemiluminescence efficiency of such compounds is dictated by the presence of electrochemical reversible redox processes rather than by their photophysical properties in terms of photoluminescence quantum yields and excited-state lifetimes. Moreover, the imidazole moiety can be alkylated enabling the insertion of a derivatizable group.

Abstract

A family of novel thermally activated delayed fluorescence (TADF) emitters has been synthesized by a straightforward and metal-free synthesis, and structurally characterized. In this work we kept the acceptor moiety, 4-(1H-imidazol-1-yl)benzonitrile, fixed and systemically tested different donors to correlate their photophysical and electrochemical properties with their performance in electrochemiluminescence using both benzoyl peroxide as co-reactant and co-reactant free (annihilation) conditions. Some compounds exceeded the efficiency of the standard [Ru(bpy)₃]Cl₂ by up to 28 times with benzoyl peroxide and 38 times in annihilation. Interestingly, we found that the efficiency is mainly dictated by the electrochemical reversibility of the redox processes rather than by the photophysical properties in terms of photoluminescence quantum yields or excited-state lifetime. In addition, the annihilation electrochemiluminescence efficiency strongly depends on the pulse sequence. The imidazole moiety can be conveniently alkylated, thus allowing the insertion of functional groups, such a carboxylic acid, and enabling practical applications.

The freer it goes, the brighter it shines. Rigid structure usually shows a positive effect on the efficiency of TADF emitters. In this work, Ph-TPA with flexible conformation of ancillary groups exhibited higher efficiency than Mc-TPA with conformationally locked ancillary groups. The macrocycle in MC-TPA made a significant contribution to the reorganization energy, leading to a severe non-radiative decay.

Abstract

Robust scaffolds were typically applied in thermally activated delayed fluorescence (TADF) molecules to suppress the non-radiative decay, trigger the fast spin-flipping, and enhance the light out-coupling efficiency. Herein, we disclosed for the first time the positive effect of flexible conformation of ancillary groups on the photophysical properties of TADF emitter. The red TADF emitter Ph-TPA with flexible conformation demonstrated small excited-state structural distortion and low reorganization energy compared to the counterpart Mc-TPA with a rigid macrocycle. Consequently, Ph-TPA showed an excellent photoluminescent quantum yield (PLQY) of 92 % and a state-of-the-art external quantum efficiency (EQE) of 30.6 % at 630 nm. This work could deepen our understanding of structure-property relationships of organic luminophores and help us to rationalize the design of efficient TADF materials.

A series of donor-π-acceptor (D-π-A) emitters are designed by adopting diphenylphosphine and phosphonium as the electron donors and acceptors. The prepared D-π-A fluorophores show intriguing thermally activated delayed fluorescence properties. The photoluminescence quantum yields and emission spectra can be tuned by the integration of metal halide units.

Abstract

Thermally activated delayed fluorescence (TADF) behaviors in metal halide perovskite and perovskite derivatives are rarely reported due to the absence of suitable TADF molecules that can serve as the A-site cations. Herein, a series of novel donor-π-acceptor type of molecules are developed by adopting substituted phosphine and phosphonium as the electron donor and acceptor linked by the polarized π-spacer. The prepared ((diphenylphosphaneyl)phenyl)diphenylphosphonium-X (BzDPP-X, X = counterions: Cl⁻, Br⁻, I⁻, NO₃ ⁻, CH₃COO⁻ etc.) salts show bright emission in the visible range with TADF characteristics due to the strong intramolecular charge transfer (ICT). Benefiting from the spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital, small singlet-triplet energy splitting (ΔE _ST) is obtained, facilitating the reverse intersystem crossing process. It turns out that the emission of BzDPP-X is dependent on the counter anions, and the counterions help to stabilize the ICT state. Intriguingly, the emission can be tuned by integrating metal-halide units into the above phosphonium salt. Remarkably, the zinc-based halide exhibits a higher photoluminescence quantum yield (36.2%) than the pure benzyl(2-(diphenylphosphaneyl)phenyl)diphenylphosphonium bromide (26.9%). This work exemplifies an easy design concept and a facile synthetic method toward ionic luminescent materials.

Au(I)-based thermally activated delayed fluorescence emitters with sterically encumbered π-extended carbene ligands are delivering highly efficient and stable vacuum-deposited organic light-emitting diodes from blue to near-infrared spectral region that realize external quantum efficiency up to 26.2% and operational lifetime (LT₉₅) up to 2082 h at a practical luminance of 1000 cd m⁻².

Abstract

Herein a class of structurally simple and operationally stable Au(I)-TADF (TADF = thermally activated delayed fluorescence) materials, based on a carbene–metal–amide (CMA) molecular scaffold comprised of sterically bulky N-heterocyclic carbene ligands with N-heterocyclic π-annulation, are reported. These CMA(Au) emitters are thermally stable, adopt coplanar or orthogonal geometry between the carbene and amide ligands, and show strong blue to deep red TADF emissions (466–666 nm) from thermally equilibrated singlet ligand-to-ligand-charge-transfer excited states with emission quantum yields of 0.63–0.99 and radiative decay rate constants of 0.68–3.2 × 10⁶ s⁻¹ in thin film samples at room temperature. The effects of increasing π-extension and orthogonal molecular geometry are similarly manifested in the reduction of both singlet–triplet energy gap and S₁ transition dipole moment. The vacuum-deposited Au(I) organic light-emitting diodes (OLEDs) display superior electroluminescence characterized by ultrahigh brightness up to 300 000 cd m⁻² and external quantum efficiencies (EQEs) up to 26.2% with roll-offs down to 2.6% at 1000 cd m⁻² alongside record-setting device lifetimes (LT₉₅) up to 2082 h. Ultrapure-green TADF-sensitized fluorescent OLEDs employing the CMA(Au) emitter as sensitizer and a multiresonance terminal emitter achieve EQEs of up to 25.3%.

An NIR-II-emissive fluorescence probe, namely DCTBT, is rationally constructed by tailoring electron donors of a conjugated molecular skeleton. DCTBT possesses bright NIR-II emission and large two-photon fluorescence action cross section, and thus achieves remarkable imaging depth for in vivo deep-brain fluorescence imaging excited at 1700 nm.

Abstract

The limited tissue penetration depth and spatial resolution are the major bottlenecks for deep-brain imaging. In this study, molecular engineering by tailoring electron donors is conducted to develop for the first time an NIR-II (second near-infrared) emissive fluorescence probe, namely DCTBT, for effective deep-brain two-photon fluorescence imaging. Benefiting from its good biocompatibility, high photostability, bright NIR-II emission as aggregates and large two-photon fluorescence action cross section at the 1700 nm excitation window, DCTBT offers the imaging depths of 2180 and 1135 µm in mouse brain with removed and intact skull, respectively. These results are the record depths for brain imaging, compared to all kinds of fluorescent probes and all modalities of multiphoton microscopy at all demonstrated excitation wavelengths. Moreover, with DCTBT labeling, hemodynamic imaging of blood flow in mouse brain vessels down to a depth of 714 µm with the intact skull is achieved. Multiphoton fluorescence imaging with the NIR-II probe DCTBT excited at the 1700 nm window may readily provide methodology for deep-brain structural and hemodynamic research.

Naphthalene-embedded multi-resonance blue emitters based on N−B−O frameworks with different structural variation for finely tuning the photophysical properties, which enables effcient narrowband emissive organic light emitting diodes have been designed and investigated.

Abstract

Great achievements have been made in the development of organic light-emitting diodes in recent decades. However, achieving high color purity for blue emitters remains a challenge. In this study, we have designed and synthesized three naphthalene (NA)-embedded multi-resonance (MR) emitters, named SNA, SNB and SNB1, based on N−B−O frameworks with isomer variations for finely adjusting the photophysical properties. These emitters show tunable blue emission with emission peaks of 450–470 nm. Small full width of half maximum (FWHM) of 25–29 nm are achieved in these emitters, indicating the well maintaining of molecular rigidity and MR effect with NA extension. Such design also ensures a fast radiative decay. However, no obvious delayed fluorescence is observed in all three emitters due to the relatively large energy differences between the first singlet and triplet excited states. Both SNA and SNB enable high electroluminescent (EL) performance in doped devices with external quantum efficiency (EQE) of 7.2 and 7.9 %, respectively. When applying the sensitized strategy, devices based on SNA and SNB show huge improvement with EQE of 29.3 and 29.1 %. More importantly, SNB with twist geometry enables stable EL spectra with almost unchanged FWHM under different doping concentrations. This work demonstrates the potential of NA extension design in constructing narrowband emissive blue emitters.

Publication date: 1 September 2023

Source: Chemical Engineering Journal, Volume 471

Author(s): Junrong Pu, Xuewei Nie, Denghui Li, Xiaomei Peng, Weidong Qiu, Wei Li, Deli Li, Guanwei Sun, Chenyang Shen, Shaomin Ji, Derong Cao, Shi-Jian Su

Chiral macrocycles composed of dimethyl 2,5-diaminoterephthalate units (n = 2–4) can be synthesised in a simple one-pot reaction. All products exhibit fluorescence in solution and in the solid state that is dependent on the size of the macrocyclic ring—the smaller the macrocycle, the longer the emission wavelength. The macrocycles show strong chiroptical activity, with the trimer showing particularly high dissymmetry factors in ECD and CPL spectra. More information can be found in the Research Article by M. Górecki, M. Grzybowski and co-workers (DOI: 10.1002/chem.202300932).

The cover shows a series of our single-benzene fluorophores. Constructing symmetrical push-pull motifs in combination with restricting bond rotations to suppress molecular motions that cause nonradiative transitions is the key to creating small, yet brightly emitting, fluorophores. The tetrahydrobenzodifuran moiety has proven to be an effective core architecture to realize single-benzene yellow fluorophores. More information can be found in the Research Article by Y. Okada and co-workers (DOI: 10.1002/chem.202301411).

Through-space charge-transfer-featured non-conjugated polymers with largely enhanced thermally activated delayed fluorescence performance are demonstrated, in which a secondary phosphine oxide acceptor is introduced to balance intra- and interchain charge transfer for radiation facilitation and non-radiation suppression, resulting in the state-of-the-art photoluminescence and electroluminescence quantum efficiencies beyond 95% and 30%, respectively.

Abstract

Through-space charge transfer (TSCT) is crucial for developing highly efficient thermally activated delayed fluorescence polymers. The balance of intra- and interchain TSCT can markedly improve performance, but it is still a big challenge. In this work, an effective strategy for “intra- and interchain TSCT balance” is demonstrated by way of a series of non-conjugated copolymers containing a 9,9-dimethylacridine donor and triazine-phosphine oxide (PO)-based acceptors. Steady-state and transient emission spectra indicate that compared to the corresponding blends, the copolymers can indeed achieve balanced intra- and interchain TSCT by accurately optimizing the inductive and steric effects of the acceptors. The DPOT acceptor with the strongest electron-withdrawing ability and the second bigger steric hindrance endows its copolymers with state-of-the-art photoluminescence and electroluminescence quantum efficiencies beyond 95% and 32%, respectively. This demonstrates that, compared to other congeners, the synergistic inductive and steric effects effectively enhance TSCT in DPOT-based copolymers for radiation, and suppress singlet and triplet quenching. The record-high efficiencies of its devices make this kind of copolymers hold the potential for low-cost, large-scale, and high-efficiency applications.

Pyrazine-based far-red to NIR-emissive boron complexes were obtained whose E _g are efficiently narrowed by boron coordination. Para- and ortho-substituted complexes were synthesized to evaluate the effects of substitution patterns. This study demonstrates that para-substitution is more suitable for constructing far-red to NIR emitters than ortho-substitution.

Abstract

We synthesized new binuclear boron complexes based on pyrazine with ortho and para substitution patterns. It was demonstrated that the para-linked complexes possess a significantly narrow energy gap between highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO), leading to their far-red to near-infrared emission properties. Meanwhile, the ortho-substituted complex showed orange emission. Considering the HOMO and LUMO distributions of pyrazine, the boron complexation to the nitrogen atoms would stabilize its LUMO more efficiently than its HOMO because a nodal plane in the HOMO passes through the two nitrogen atoms. The theoretical study suggests that the para-substitution would not significantly perturb such a characteristic HOMO distribution originating from pyrazine in stark contrast to the ortho-substituted one. As a result, the HOMO-LUMO gap of the para-linked complex is dramatically narrower than that of the ortho-linked one.

Owing to the quasi-host-guest system formed by a separated host layer and ultrathin thermally activated delayed fluorescence emission layer, highly efficient doping-free organic light-emitting diodes (OLEDs) are achieved with comparable performance to conventional doped ones. Device optimization could be realized by simple thickness regulation, while the introduction of an interfacial exciplex structure can further boost device efficiency. Such a novel ultrathin emission layer strategy meeting efficiency and cost demands holds great promise for doping-free OLEDs.

Abstract

Doping-free organic light-emitting diodes (OLEDs) are beneficial to reduce manufacturing costs for mass production, which, however, are limited by the ubiquitous aggregation-caused quenching (ACQ) effect, especially for thermally activated delayed fluorescence (TADF) emitters with relatively long exciton lifetimes. Herein, two typical TADF emitters pACRS and pACRSO with different sulfur atom valence states are developed, where pACRS with a thioether unit exhibits suppressed intermolecular interaction, alleviated ACQ effect, and higher efficiency in a conventional doping-free device, in contract to pACRSO with a sulfone unit. It is of interest that comparable efficiencies are achieved for both emitters in doping-free OLEDs with an ultrathin emission layer (UEML), in which the emitter molecules are deposited onto the surface of the underlying organic layer of host material to form an ultrathin quasi-host-guest system with alleviated ACQ effect. Besides, the suppressed trap effect is the key to guarantee the efficiency of UEML-OLEDs, while different intermolecular interactions of emitters that determine the optimized UEML thickness will affect the efficiency roll-off. Furthermore, benefiting from the UEML structure, highly efficient doping-free OLEDs are also successfully achieved for red TADF emitters with stronger intermolecular interactions. Such an UEML strategy meeting efficiency and cost demands holds great promise for doping-free OLEDs.

Exciton dynamics in blue fluorescence organic light emitting diodes based on an aggregation–induced emission molecule with the “hot exciton” property are thorougly investigated, and the possible exciton loss channels in the electroluminescence process are determined.By strategically managing the structures of devices, the resulting device achieves a maximum external quantum efficiency of 12.5% with a long operational lifetime.

Abstract

“Hot exciton” molecules that allow the transition of excitons from a high-lying triplet state (T_n, n≥ 2) to singlet states (S_m, m≥1) by a reverse intersystem crossing (hRISC) process have become an effective strategy to achieve high efficiency fluorescence organic light emitting diodes (OLEDs). However, the understanding of the dynamic behavior of the “hot exciton” process is still very lacking. Herein, the exciton dynamics of an aggregation-induced emission (AIE) molecule TPA-An-mPhCz with the “hot exciton” property are deeply investigated, and the proportion between hRISC and internal inversion (IC) of excitons on T_n is successfully quantified by in situ transient electroluminescent measurements and theoretical calculation. It is found that the IC process increases severe energy loss of T_n excitons. By introducing a triplet–triplet annihilation up-conversion layer in the emissive layer to efficiently recapture the IC excitons and further doping a blue fluorescent emitter in the TPA-An-mPhCz layer to achieve high photoluminescence quantum yield (PLQY), the resulting OLED achieves a maximum external quantum efficiency of 12.5% with negligible efficiency roll-off. More impressively, the operational lifetime LT₇₅ (lifetime to 75% of the initial luminance) of the device with efficient triplets utilization performs a remarkable 116 h under 1000 cd m⁻². This work provides the fundamentals for the design of hot exciton materials with efficient exciton utilization to develop efficient blue fluorescence OLEDs.

Narrowband organic afterglow materials are achieved via a phosphorescence Förster resonance energy transfer process by the combination of the long-lived phosphorescence donor and narrowband emission feature of the fluorescence acceptor. The resulting materials exhibit high color purity and multicolor narrowband afterglow, demonstrating potential in high-resolution afterglow displays and instant information identification.

Abstract

Achieving multicolor organic afterglow materials with narrowband emission and high color purity is important in various optoelectronic fields but remains a great challenge. Here, an efficient strategy is presented to obtain narrowband organic afterglow materials via Förster resonance energy transfer from long-lived phosphorescence donors to narrowband fluorescence acceptors in a polyvinyl alcohol matrix. The resulting materials exhibit narrowband emission with a full width at half maximum (FWHM) as small as 23 nm and the longest lifetime of 721.22 ms. Meanwhile, by pairing the appropriate donors and acceptors, multicolor and high color purity afterglow ranging from green to red with the maximum photoluminescence quantum yield of 67.1% are achieved. Moreover, given their long luminescence lifetime, high color purity, and flexibility, the potential applications are demonstrated in high-resolution afterglow displays and dynamic and quick information identification in low-light conditions. This work provides a facile approach for developing multicolor and narrowband afterglow materials as well as expands the features of organic afterglow.