High Exciton Research Articles

Enhancing photocatalytic performance of covalent organic frameworks via ionic polarization.

Covalent organic frameworks have emerged as a thriving family in the realm of photocatalysis recently, yet with concerns about their high exciton dissociation energy and sluggish charge transfer. Herein, a strategy to enhance the built-in electric field of series β-keto-enamine-based covalent organic frameworks by ionic polarization method is proposed. The ionic polarization is achieved through a distinctive post-synthetic quaternization reaction which can endow the covalent organic frameworks with separated charge centers comprising cationic skeleton and iodide counter-anions. The stronger built-in electric field generated between their cationic framework and iodide anions promotes charge transfer and exciton dissociation efficiency. Moreover, the introduced iodide anions not only serve as reaction centers with lowered H* formation energy barrier, but also act as electron extractant suppressing the recombination of electron-hole pairs. Therefore, the photocatalytic performance of the covalent organic frameworks shows notable improvement, among which the CH3I-TpPa-1 can deliver an high H2 production rate up to 9.21 mmol g-1 h-1 without any co-catalysts, representing a 42-fold increase compared to TpPa-1, being comparable to or possibly exceeding the current covalent organic framework photocatalysts with the addition of Pt co-catalysts.

Grain size control in quasi-two-dimensional perovskite thin film via intermediate phase engineering for efficient bound exciton generation

AbstractQuasi-two dimensional (2D) perovskites have emerged as a promising class of materials due to their remarkable photoluminescence efficiency, which stems from their exceptionally high exciton binding energies. The spatial confinement of excitons within smaller grain sizes could enhance the formation of biexcitons leading to higher radiative recombination efficiency. However, the synthesis of high-quality quasi-2D perovskite thin films with controllable grain sizes remains a challenging task. In this study, we present a facile method for achieving quasi-2D perovskite thin films with controllable grain sizes ranging from 500 to 900 nm. This is accomplished by intermediate phase engineering during the film fabrication process. Our results demonstrate that quasi-2D perovskite films with smaller grain sizes exhibit more efficient bound exciton generation and a reduced stimulated emission threshold down to 15.89 µJ cm−2. Furthermore, femtosecond transient absorption measurements reveal that the decay time of bound excitons is shorter in quasi-2D perovskites with smaller grain sizes compared to that of those with larger grains at the same pump density, which is 230.5 ps. This observation suggests a more efficient exciton recombination process in the smaller grain size regime. Our findings would offer a promising approach for the development of efficient bound exciton lasers.

Pure room temperature phosphorescence emission in nondoped OLEDs: adjustable oxidation states and excited-state modulation.

Purely organic room temperature phosphorescence (RTP) materials are a new kind of triplet emitter, which can harvest both singlet and triplet excitons in theory, thus showing great application potential for organic light-emitting diodes (OLEDs). However, nondoped OLEDs based on RTP emitters have been rarely explored owing to challenges in realizing efficient phosphorescence in single-component systems. Herein, three donor-acceptor-type luminogens were designed and synthesized in which phenothiazine, with different oxidation degrees, acted as the electron donor and acetophenone as the acceptor. The adjustable oxidation states of phenothiazine enabled the modulation of excited states, facilitating the transition from dual RTP and thermally activated delayed fluorescence emissions to pure RTP. A nondoped OLED device was then fabricated based on the pure RTP emitter, achieving a high exciton utilization efficiency of 86%, clearly demonstrating the enhancement of electroluminescence performance through RTP properties.

Charge transfer between layers of polymeric carbon nitride driven by surface grafting phosphotungstic polyanions toward efficient photocatalytic hydrogen evolution

It is a challenging issue to achieve efficient charge transfer between layers for the layered polymer photocatalysts, because the photogenerated carriers would prefer random migration within layers and thus have high reverse recombination rate due to their inherent anisotropy and high exciton binding energy. Herein, an innovative surface grafting strategy is developed to modify the layered polymeric carbon nitride (PCN) making use of phosphotungstic (PWO) polyanions. The surface coupling effect of PWO on PCN effectively improves reduction ability and utility rate of luminous energy through shifting the conduction band (CB) upward and broadening light absorption range to cover near infrared region up to 1000 nm, respectively. In especial, the strong electron-withdrawing effect of surface PWO moieties can reduce layer spacing to shorten electron transfer path and attract the photogenerated electrons transfer from PCN matrix to surface, thus conquering the charge transfer restriction between layers to improve the carrier separation efficiency. As a result, the photocatalytic hydrogen evolution (PHE) performance is dramatically enhanced. The optimal PWO-PCN-1% sample achieves an average PHE rate of 9.6 times that of PCN, stable operation for a total of 28 h on 7 cycles, and an AQY up to 22.3% at 400 nm. This contribution affords a viable modification avenue to overcome the limitation of charge transfer between layers for layered polymer photocatalysts.

Flexible Hybrid Membrane with Synergistic Exciton Dynamics for Excessive 280 h of Durably Piezo-Photocatalytic H2O-to-H2 Conversion.

Solar-driven H2O-to-H2 conversion is a feasible artificial photoconversion technology for clean energy production. However, low photon utilization efficiency has become a major obstacle limiting the practical application of this technology. Herein, a metal atomic replacement (Sb→Ni) is conducted to disintegrate bulk Sb2S3 nanorods and synchronously grow the NiS nanolayers, and a flower-like Sb2S3-NiS nanocomposite with high BET specific surface area and synergistic exciton dynamics is constructed for simulated solar (SSL)-driven H2O-to-H2 conversion. The optimal Sb2S3-NiS nanocomposite is compounded with polyvinylidene fluoride (PVDF) to prepare a flexible PVDF/Sb2S3-NiS (PSN) hybrid membrane with stable structure and excellent recyclability via an electrospinning method. Due to the synergistically interacted organic-inorganic interface and high porosity, it is conducive to the exposure of effective active sites, exciton conduction and mass transfer and exchange, thereby an outstanding alkaline (Ph=13.0) H2O-to-H2 conversion activity with a 0.06% of solar-to-hydrogen efficiency and over 280 h (70 cycles) of durable recycling is achieved under the collaborative drives of SSL and weak ultrasound (40 Hz). This study raises a state-of-the-art membrane material for solar-driven panel reaction technology.

Monolayer MoS2 and WS2 for Vertical Circular‐ Polarized‐Light‐Emitting Diode: from Fundamental Understanding to Device Architecture

AbstractLight‐emitting diodes (LEDs) have revolutionized lighting and displays due to their numerous advantages over conventional lighting mechanisms. Moreover, the directional nature of luminescent materials has spurred significant advancements in the development of circularly polarized LEDs, which hold transformative potential for applications in biomedical imaging, liquid crystal displays, spintronics, and valleytronics. The performance of circularly polarized LEDs mainly depends on the emitter material, which is this study's focus. In particular, semiconducting‐phase 2D monolayer MoS2 and WS2 are attractive emitter‐material candidates owing to their bandgap versatility, high carrier mobility, high exciton binding energy, polarized‐light‐emission properties, and unique spin–valley coupling. Several works have examined the fundamental light‐emission properties of monolayer MoS2 and WS2 from the perspectives of optoelectronic concepts, material fabrication, and device construction. This paper presents approaches to control, tune, and enhance these properties of monolayer MoS2 and WS2. Possible guidelines for monolayer‐material synthesis (top‐down and bottom‐up approaches) and device engineering of vertically stacked MoS2 and WS2 are presented. Finally, the review considers the material topological characteristics, outlines the challenges and potential of monolayer MoS2 and WS2 for developing high‐performance commercial circularly polarized LED devices, and proposes a technological roadmap for leveraging other monolayer transition metal dichalcogenide systems in optoelectronic devices.

Self-powered Schottky barrier photodetectors based on P3HT:PC61BM bulk heterojunction films

By employing the classic system poly(3-hexylthiophene-2,5-diyl): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM), organic bulk heterojunction films were applied on an indium tin oxide substrate using a one-step spin-coating method, without requiring any complex manufacturing processes, to obtain self-powered photodetectors (PDs) with a simple preparation process. The fullerene material was introduced to create a bulk heterojunction film with proper phase separation and greatly enrich the donor/acceptor dissociation interface, thus improving the high exciton binding energy and short exciton diffusion distance. The built-in electric field formed by the Schottky junction at the interface between the active layer and electrode can enhance the separation of excitons and the transport of charge carriers, realizing optical detection without external energy sources. Moreover, femtosecond transient absorption was employed to investigate the exciton dynamics in organic films and analyze the working mechanism of self-powered detection performance. The long-lived behavior of carriers and the formation of charge transfer states were further verified, which contributed to the enhanced performance of the device. As a result, the self-powered PD-based Schottky bulk heterojunction presents a high light on/off ratio of over 104 (0 V) and fast response speed with rise and decay times of 33 and 36 µs, respectively, under a 532 nm light illumination. These results provide theoretical and experimental verification of this technique for the development of self-powered PDs in the field of organic materials.

A Perspective on 2D Fused-Ring Quad-Rotor-Shaped Nonfullerene Acceptors with an Anthracene Core.

Previous studies have demonstrated the remarkable properties of quad-rotor-shaped two-dimensional nonfullerene acceptors (2D NFAs), which encompass exceptional electron affinity, robust sunlight absorption, effective exciton separation, and accelerated electron transfer capabilities. Naphthalene has been demonstrated to be a significant 2D fused core to construct high-performance 2D NFAs. However, synthesizing such materials through existing synthetic pathways poses a significant challenge. In this work, we designed four 2D NFAs (TEA-SIC, TEA-SIC-8F, TEA-SIC-OH, and TEA-SIC-OH-8F) with an anthracene core. These NFAs can theoretically be synthesized into a quad-rotor configuration through a seven-step synthetic process. Theoretical calculations have demonstrated that these 2D NFAs exhibit superior electron-accepting abilities, enhanced sunlight absorption, and more efficient exciton dissociation compared to Y6. Furthermore, TEA-SIC and TEA-SIC-8F exhibited impressive electron mobilities of 1.76 × 10-3 cm2 V-1 s-1 and 1.18 × 10-3 cm2 V-1 s-1, respectively, indicating their suitability for the development of high-performance organic solar cells (OSCs). Although TEA-SIC-OH and TEA-SIC-OH-8F have lower electron mobility, their high sunlight absorption and efficient exciton separation suggest potential as third components in ternary OSCs. These 2D NFAs also exhibit a commendable solubility in most alcohol-based solvents, indicating their potential for specialized applications in the fabrication of stacked OSCs. These findings provide valuable insights for the future design of synthesizable high-performance 2D NFAs.

Constructing Organic Phosphorescent Scintillators with Enhanced Triplet Exciton Utilization Through Multi‐Mode Radioluminescence for Efficient X‐Ray Imaging

AbstractThe development of organic phosphorescent scintillators with high exciton utilization efficiency has attracted significant attention but remains a difficult challenge because of the inherent spin‐forbidden feature of X‐ray‐induced triplet excitons. Herein, a design strategy is proposed to develop organic phosphorescent scintillators through thermally activated exciton release to convert stabilized spin‐forbidden triplet excitons to spin‐allowed singlet excitons, which enables singlet exciton‐dominated multi‐mode emission simultaneously from the lowest singlet, triplet, and stabilized triplet states. The resultant scintillators demonstrate a maximum photoluminescence efficiency of 65.8% and a minimum X‐ray radiation detection limit of 110 nGy s−1; this allows efficient radiography imaging with a spatial resolution of ≈10.0 lp mm−1. This study advances the fundamental understanding of exciton dynamics under X‐ray excitation, significantly broadening the practical use of phosphorescent materials for safety‐critical industries and medical diagnostics.

Growth of anthracene microcrystals by the micro-space sublimation method and their photophysical properties

Anthracene and its derivatives are widely utilized in optoelectronic devices due to their unique properties. Generally, single-crystal structures can avoid non-radiative recombination, enhance carrier mobility, and ultimately improve device performance. In this work, anthracene microcrystals were prepared using the micro-space sublimation method. Through real-time in-situ observation, the crystallization dynamics of anthracene molecules were revealed. Unlike traditional vacuum evaporation deposition technique, the close proximity of the substrate to the source facilitates the self-assembly of anthracene molecules into an ordered crystal structure. Six peaks can be observed in the photoluminescence spectrum, corresponding to various lowest excited state decay processes. The fluorescence intensity at the peak of 423 nm decreases significantly with increasing temperature. The reason for this is the relatively high exciton binding energy, which makes excitons more stable and easier to form. The lattice vibrations induced by increased temperature were found to affect the transport and separation of excitons. Time-resolved fluorescence spectroscopy imaging revealed that a relatively uniform distribution of fluorescence lifetimes in the anthracene microcrystals, indicating high crystallization quality. This work provides valuable insights for controlling the morphology and investigating the photophysical properties of organic semiconductors.

Deep blue high-efficiency solution-processed triplet-triplet annihilation organic light-emitting diodes using bis(8-carbazol-N-yl)fluorene- and benzonitrile-modified anthracene/chrysene fluorescent emitters

Triplet-triplet annihilation (TTA) emitters can effectively utilize non-radiative triplet excitons through the interaction of low triplet energy excitons to produce high energy singlet excitons, but they are mostly restricted by their multilayered device structure fabricated using layer-by-layer thermal vacuum evaporation. It is a great challenge to develop, for the first time, efficient solution-processed non-doped TTA organic light-emitting diodes (OLEDs). In this study, two solution-processable blue emissive TTA molecules (FAnCN and FCsCN) bearing (anthracen-9-yl)benzonitrile (AnCN) and (chrysen-6-yl)benzonitrile (CsCN) as TTA emissive cores modified with 9,9′-bis(8-(carbazole-N-yl)octyl)fluorene (F) are designed and synthesized, respectively. The experimental and theoretical studies reveal that both molecules exhibit deep blue emissions, amorphous morphology with good thermal stability, high-quality solution-cast thin films, decent hole mobility, high-lying HOMO levels (∼-5.45 eV), and suitable lowest singlet (S1)/triplet (T1) excited states (2T1 > S1) for TTA process. FAnCN and FCsCN are successfully employed as solution-processed non-doped emissive layers (EML) in simple structured TTA OLEDs. These devices show intense blue emissions, low turn-on voltages (∼3.6 V), excellent electroluminescent (EL) performances (EQEmax = 5.47–6.84 % and LEmax = 5.66–5.83 cd/A), and TTA characteristics. Especially, FCsCN-based TTA OLED emits deep blue EL emission peaked at 435 nm with a high EQEmax of 6.84 %. This work not only presents a new strategic design for the preparation of solution-processable TTA emitter, but also further ratifies that the TTA mechanism can also be applicable in solution-processed OLEDs.

Toward Enhanced Biomimetic Artificial Visual Systems Based on Organic Heterojunction Optoelectronic Synaptic Transistors

AbstractArtificial visual systems, inspired by the human eye, hold significant potential in artificial intelligence. Optoelectronic synapses, integrating image perception, processing, and memory in a single device, offer promising solutions. The human eye exhibits different recognition accuracies for objects under varying light conditions. Therefore, a more biomimetic visual system is needed to better fit actual application scenarios. Here, an organic heterojunction‐based optoelectronic synaptic transistor (OHOST) is proposed to enhance biomimetic artificial visual systems. By utilizing the excellent carrier capture ability of core‐multi‐shell quantum dots (QDs) and the high exciton dissociation efficiency of heterojunction interfaces, the device achieves a recognition capability under different light intensities closely resembling that of the human eye. Under optimal light intensity, the recognition accuracy for the modified national institute of standards and technology (MNIST) dataset can reach 91.52%. Nevertheless, under both low and high light intensities, the accuracy drops to a low level. This work pushes the development of artificial visual systems toward higher levels of biomimicry.

High Efficiency Non‐Doped Organic Light Emitting Diodes Based on Pure Organic Room Temperature Phosphorescence by High‐Lying Singlet Exciton Fission

AbstractHeavy‐metal‐free pure organic room temperature phosphorescence (ORTP) holds great potential in the field of organic optoelectronic devices owing to low economic cost, simple preparation techniques, and high exciton utilization. However, it is still filled with challenges in realizing high efficiency organic light‐emitting diodes (OLEDs) and exploring the internal physical mechanism based on these ORTP molecules. Here, a high‐performance OLED induced by an unexpected interfacial spin‐mixing process between the ORTP molecule and interlayers is demonstrated, and the high efficiency electroluminescence (EL) mechanism is studied through magneto–electroluminescence (MEL) and magneto–photoluminescence (MPL) measurements. The steady‐state and transient PL properties imply that the interfacial effect is related to a high‐lying singlet fission (HLSF) process in the ORTP molecule itself. Further, the HLSF process and the corresponding energy level position are confirmed by the incident wavelength‐ and temperature‐dependent PL spectra and the magnetic‐field‐dependent transient PL. Finally, by optimizing the interfacial material adjacent to the emissive layer to utilize this interfacial spin mixing effect, a high‐efficiency non‐doped ORTP‐OLED with external quantum efficiency of 16% and CIE coordinates of (0.27, 0.49) is developed. The proposed mechanism during the EL process will give insight to produce more efficient OLEDs based on ORTP materials in the future.

High-performing organic/quantum dot hybrid upconversion device based on a single-component near-infrared-sensitive layer

A donor/acceptor (D/A) heterojunction with an interfacial energetic offset is demonstrated to enable efficient exciton dissociation in organic photodetectors and upconversion devices (UCDs). Unfortunately, this approach usually encounters complicated optimization procedures and interfacial instability. Herein, we present an alternative strategy for achieving high-performing UCDs by utilizing an organic single-component near-infrared (NIR)-sensitive layer instead of a D/A heterojunction. The showcased UCD is constructed by vertically stacking an organic single-component Y6 NIR-detection unit and a quantum dot light-emitting unit. Due to the high dielectric constant and low exciton binding energy of the non-fullerene acceptor Y6, free carriers are directly and spontaneously generated upon NIR light excitation. As a result, the single-component UCD achieves a low light detection capability of 2.5 μW/cm2, a fast refresh rate of >3.8 × 104, and a high resolution exceeding 1100 dpi, providing a stable optical response to high-frequency NIR signals and high-quality NIR imaging.

Construction of Concentration Quenching‐Resistant Multi‐Resonance TADF Emitters via Positional Isomerization for OLEDs

AbstractMultiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters are promising for high‐definition organic light‐emitting diodes (OLEDs) due to their high exciton utilization and color purity. However, strong interchromophore interactions cause most MR‐TADF emitters with planar structures to aggregate at high doping concentrations, leading to degraded efficiencies. Herein, using benzenesulfonyl‐functionalized dibenzothiophene sulfoximine with steric effects, three MR‐TADF emitters (2SBN, 3SBN, and 4SBN) are synthesized by coupling the classic DtBuCzB skeleton at different sites. Three emitters exhibit green or blue‐green emission with full width at half maximum (FWHM) values less than 29 nm and photoluminescence quantum yields exceeding 90%. OLEDs based on 2SBN, 3SBN, and 4SBN achieve high maximum external quantum efficiency (EQEmax) values of 30.1%, 27%, and 33.8%, respectively, at a 5 wt.% doping concentration. Notably, due to the distorted conformation of 4SBN and suppressed intermolecular interaction, the OLED remains high EQEmax of 28.9% at a doping concentration of 20 wt.%. These results demonstrate the feasibility of molecular design to modulate spatial conformations via positional isomerism to develop MR‐TADF emitters with reduced concentration quenching.

Disorder–order structure of a-CeO2/SnFe2O4 heterojunction with enhanced exciton dissociation for the NIR-driven photocatalysis

Strong Coulomb force between photogenerated electrons and holes often results in high level exciton pairs during the photocatalytic process, which hinders the formation of reactive oxygen species (ROS) in the photocatalytic reaction, particularly for the photocatalysis under near infrared (NIR) irradiation. Hence, it is crucial to dissociate excitons into free carriers. In this study, we propose a novel amorphous–crystalline heterojunction of a-CeO2/SnFe2O4 for the NIR-driven photocatalytic degradation and sterilization. The introduction of disorder–order interface in heterojunction could greatly enhance the built-in electric field, thereby serving for exciton dissociation. Additionally, the presence of oxygen vacant sites in the a-CeO2/SnFe2O4 system can effectively modulate the electronic structure of the material, facilitating exciton dissociation in conjunction with the built-in electric field. The DFT simulation proved the positive impact of the disorder–order interface on charge separation, as well as its enhancement on the activation of O2 and H2O molecules. This work provides a theoretical support for the creation of disorder–order interface to promote exciton dissociation and enhance photocatalytic performance.

Donor polarization engineering of conjugated microporous polymers to boost exciton dissociation for photocatalytic degradation of tetracycline

The misuse and inevitable release of antibiotics can cause significant harm to both human health and the environment, and the use of polymeric semiconductors for photodegradation of antibiotics in aqueous environments is one of the most effective strategies to alleviate the current dilemma. Nevertheless, the inherently high exciton binding energy (Eb) and low photogenerated carrier transfer efficiency for most photocatalysts results in unsatisfactory photodegradation performance. Hence, this work proposes a donor polarization strategy to regulate the exciton dissociation of conjugated microporous polymers (CMPs) by minimizing their Eb. Results exhibited that the introduction of the strong donor unit 3,4-ethylenedioxythiophene (EDOT) not only reduces the Eb and effectively promotes exciton dissociation, but also broadens the visible light absorption of CMP. Among them, EdtTz-CMP with the lowest Eb (99 meV) delivered an efficiency of 94.6% in photocatalytic degradation of tetracycline (TC) with in 90 min, significantly higher than those of its analogues. This work provides a viable approach to design CMPs by tuning the intrinsic dipole of the donor for efficient environmental purification.

Influence of Growth Temperature on Morphological and Structural Properties of Sputtered- Zinc Oxide Nanorods

Zinc oxide is highly sought after for several applications in biology, optoelectronics, electronics, and sensing. Zinc oxide nanorods exhibit a high exciton binding energy and a wide direct band gap, making them an attractive material for ultraviolet optoelectronic devices in the compound semiconductor field. This investigation focuses mainly on the influence of growing temperature on the crystal structure and surface morphology of ZnO nanorods, specifically for their application as UV photodetectors. Si (100) substrates were utilized for the growth of ZnO nanorods using radio frequency magnetron sputtering. The ZnO nanorods are grown at temperatures of 350 °C, 375 °C, and 400 °C, respectively. The crystal structure and surface morphology were examined using X-ray diffraction and scanning electron microscopy. The samples exhibited a same crystal orientation of the (002) diffraction peak at all growth temperatures. The growth temperatures show a direct influence on the density and length of nanorods, as evidenced by the scanning electron microscopy photographs. The results revealed the significant influence of substrate temperature on the regulation of nanorod length and crystal formation.

Asymmetric Structural Engineering of Hot-Exciton Emitters Achieving a Breakthrough in Non-Doped BT.2020 Blue OLEDs with a Record 9.5% External Quantum Efficiency.

High-efficiency non-doped deep-blue organic light-emitting diodes (OLEDs) meeting the standard of BT.2020 color gamut is desired but rarely reported. Herein, an asymmetric structural engineering based on crossed long-short axis (CLSA) strategy is developed to obtain three new deep-blue emitters (BICZ, PHDPYCZ, and PHPYCZ) with a hot-exciton characteristic. Compared to 2BuCz-CNCz featuring a symmetric single hole-transport framework, these asymmetric emitters with the introduction of different electron-transport units show the enhancement of photoluminescence efficiency and improvement of bipolar charge transport capacity. Further combined with high radiative exciton utilization efficiency and light outcoupling efficiency, the non-doped OLED based on PHPYCZ exhibits the best performance with an excellent current efficiency of 3.49%, a record-high maximum external quantum efficiency of 9.5%, and a CIE y coordinate of 0.049 approaching the BT.2020 blue point. The breakthrough obtained in this work can inspire the molecular design of deep-blue emitters for high-performance non-doped BT.2020 blue OLEDs.

Deep-blue electroluminescence with orthogonal donor-acceptor structure: The role of charge-transfer excited state component in hybrid local and charge-transfer (HLCT) excited state

In this work, three orthogonally bonded phenanthroimidazole based donor-acceptor (D-A) structured blue-emissive materials N-SBPMCN, N-ABPMCN and N-TBPMCN with different donor moieties are designed synthesized. Theoretical combined experimental researches proved that the involving of weak donor (spiro-fluorene and anthracene) and strong donor triphenylamine can form different locally-emissive (LE) dominated hybrid local and charge-transfer (HLCT) excited state, which can contribute to their high photoluminescent quantum yield (PLQY), satisfied electroluminescence performance and blue purity. Specifically, N-TBPMCN with strong donor triphenylamine that possesses more CT excited state components demonstrates the best electroluminescence performance and blue purity among the three materials, revealing that the molecular design of orthogonal D-A structure is of great potential in blue-emissive functional materials. Additionally, we also discovered that intermolecular CT state can also contribute to high exciton utilization.