Exciton Lifetime Research Articles

Coupling and Energy Transfer between an Exciton in a Semiconductor Quantum Dot and a Surface Plasmon in a Metal Nanoparticle.

The coupling between excitons in semiconductors or molecules and metal nanoparticles has been well-studied, primarily for nanoparticles in their ground electronic state. However, less attention has been given to exciton-nanoparticle interactions when the nanoparticle generates surface plasmons upon incident excitation. In this study, we explore the coupling and energy transfer dynamics between an exciton and the surface plasmon of a metal nanoparticle, forming a "plexciton". Significant mutual energy exchange between the exciton and the plasmon leads to unexpected effects on the exciton lifetime and coupling strength. The interaction at varying wavelengths, orientations, magnitudes, and phases was studied. Our results show that the exciton decay rate can be quenched entirely when the plasmon's energy compensates for that of the exciton radiative decay, even at separation distances of several hundred nanometers. These findings highlight the impact of surface plasmons on exciton dynamics, opening new possibilities for enhancing charge carrier dynamics in coupled systems.

Nanofibers based on MEH‐PPV‐P3HT: Elaboration and characterization

AbstractOne‐dimensional polymer‐based nano‐structures such as nanofibers and nanotubes are intensively investigated since they show improved properties, as well as new paradigms for optical, optoelectronic, and photonic devices. The main objective of this work is oriented to synthesize of nanofibers based on a new conjugated copolymer MEHPPV‐P3HT. In this direction, the synthesis procedure of MEHPPV‐P3HT nanofibers and nanotubes is presented in detail. Interestingly, the morphological, structural, and vibrational studies of the elaborated nanofibers are achieved. They show that MEHPPV‐P3HT impregnated nanofibers begin as solid cylinders and end up as nanotubes with a nominal diameter of nearly 200 nm. The confinement effect or nanostructuration effect seems to be signed and appears in the large changes in photophysical properties. Stationary and transient photoluminescence reveal a new molecular arrangement and an enhancement of exciton average life time that is doubled in nanofibers with respect to the film.Highlights Nanostructuring of MEHPPV‐P3HT nanofibers by template method Morphological and spectroscopic characterization of confined nanofibers Effects of nanometric confinement on photophysical properties Enhancing exciton lifetimes in MEHPPV‐P3HT nanofibers

Incorporation of selenophene into thienoazacoronene-based nonfullerene acceptor: impact on photophysical and photovoltaic properties

Abstract The singlet exciton (S1) lifetime of nonfullerene acceptor (NFA) films is a crucial factor influencing their photovoltaic performances, as a longer S1 lifetime increases the exciton diffusion length. We previously reported that a NFA with a two-dimensionally π-extended thienoazacoronene (TAC) central core, S-TACIC, exhibits an exceptionally long S1 lifetime in the film. In this study, we examined the effects of replacing thiophene with selenophene on the photophysical and photovoltaic properties. Fluorescence decay measurements showed that the S1 lifetime of the selenophene-substituted TAC-based NFA (Se-TACIC) is longer in solution (500 ps) but significantly shorter in the film (<200 ps) compared to S-TACIC (220 ps in solution and 1,590 ps in film). When blended with the polymer donor PBDB-T, the Se-TACIC-based organic photovoltaic (OPV) device exhibited a lower power conversion efficiency (5.58%) than the S-TACIC-based one (9.92%), due to inferior photovoltaic parameters of the Se-TACIC-based OPV device.

Correlating photochemical H2 production and excited state lifetimes of heterostructured and doped ZnCdS nanoparticles.

A variety of ZnCdS-based semiconductor nanoparticle heterostructures with extended exciton lifetimes were synthesized to enhance the efficacy of photocatalytic hydrogen production in water. Specifically, doped nanoparticles (NPs), as well as core/shell NPs with and without palladium and platinum co-catalysts, were solubilized into water using various methods to assess their efficacy for solar H2 fuel synthesis. The best results were obtained with low bandgap ZnCdS cores and ZnCdS/ZnS core/shell NPs with palladium co-catalysts. The results, augmented with DFT and tight binding electronic structure calculations, revealed the importance of exciton charge carrier separation via tunneling. While the systems studied here were photocatalytically active, they nonetheless lagged behind the quantum efficiency observed from "gold standard" CdSe/CdS·Pt dot-in-rod nanoparticles as evident from quantum efficiencies that were estimated to be 0.5 → 2%.

Multifunctional luminogens with synergy of aggregation-induced delayed fluorescence, two-photon absorption and photocurrent generation.

In this study, we investigated the aggregation-induced delayed fluorescence (AIDF) properties of three luminogens - TN, TA, and TP. Our comprehensive theoretical analysis reveals a significant reduction in the ΔEST in their aggregated or solid-state, activating TADF, on a ∼μs time-scale. Additionally, these luminogens demonstrate two-photon excited anti-Stokes photoluminescence emission and improved photocurrent generation, attributed to their strong charge transfer characteristics and longer singlet exciton lifetimes.

Exciton-Polaron in a Quasi-One-Dimensional Chain of Hexyl-Diammonium-BiI5 Octahedra.

Lower-dimensional organic-inorganic hybrid perovskite materials promise to revolutionize the optoelectronics industry due to the tremendous possibilities of exotic control on excitonic properties driven via quantum confinement. Flexible organic cations acting as spacers and stabilizers enhance electron-phonon couplings, further amplifying the potential for modular light-matter interactions in these materials. Herein we unravel the nature of excitons in a quasi-1D chain of corner-sharing bismuth iodide octahedra with an intrinsic quantum well structure stabilized by a hexyl-diammonium cation. Using broadband femtosecond impulsive Raman spectroscopy and detailed electronic structure calculations, we directly quantify the exciton lifetime along with the electron-phonon coupling constants to fully describe the excitation as an exciton-polaron. We find ∼30 times larger electron-phonon couplings beyond the standard 2D-hybrid perovskite materials along with picosecond time-scale decoherences, thereby shedding light for the first time on the immense potential of these 1D perovskite analogues for developing novel materials for efficient light-conversion technologies.

Visualization and Estimation of 0D to 1D Nanostructure Size by Photoluminescence.

We elaborate a method for determining the 0D-1D nanostructure size by photoluminescence (PL) emission spectrum dependence on the nanostructure dimensions. As observed, the high number of diamond-like carbon nanocones shows a strongly blue-shifted PL spectrum compared to the bulk material, allowing for the calculation of their top dimensions of 2.0 nm. For the second structure model, we used a sharp atomic force microscope (AFM) tip, which showed green emission localized on its top, as determined by confocal microscopy. Using the PL spectrum, the calculation allowed us to determine the tip size of 1.5 nm, which correlated well with the SEM measurements. The time-resolved PL measurements shed light on the recombination process, providing stretched-exponent decay with a τ0 = 1 ns lifetime, indicating a gradual decrease in exciton lifetime along the height of the cone from the base to the top due to surface and radiative recombination. Therefore, the proposed method provides a simple optical procedure for determining an AFM tip or other nanocone structure sharpness without the need for sample preparation and special expensive equipment.

A Novel Matrix-Free Hyperfluorescent System Based on Anti-Quenching TADF Host for High Color Purity MR-TADF Emitters.

Organic light-emitting diodes (OLEDs) based on hyperfluorescent system have attracted widespread attention due to their ability to simultaneously achieve improvements in efficiency, lifetime, and color purity by combining the advantages of high exciton utilization sensitizers and high-color purity emitters. Traditional hyperfluorescent systems typically involve three or four components and are severely sensitive to the doping concentration (≈0.5 wt%) of a terminal emitter, which inevitably causes high costs and difficulties in reproducibility. Here, a novel design concept for a matrix-free hyperfluorescent (MFHF) system that employs a combination of an anti-quenching TADF host and a high color purity MR-TADF emitter is proposed. This strategy allows traditional concentration-sensitive MR-TADF emitters to significantly improve exciton utilization and reduce exciton lifetime at high doping levels, without the need for complex molecular modifications. The OLEDs with binary emissive layer achieve pure-green emission, a maximum external quantum efficiency of over 30%, and a high maximum power efficiency of 145lmW-1. The approach offers a straightforward and universal method to achieve anti-quenching matrix-free hyperfluorescent OLEDs with high color purity, making them promising for commercial applications in low-cost ultra-high-definition (UHD) displays.

Benzothiadiazole‐Fused Cyanoindone: A Superior Building Block for Designing Ultra‐Narrow Bandgap Electron Acceptor with Long‐Range Ordered Stacking

AbstractThere are great demands of developing ultra‐narrow bandgap electron acceptors for multifunctional electronic devices, particularly semi‐transparent organic photovoltaics (OPVs) for building‐integrated applications. However, current ultra‐narrow bandgap materials applied in OPVs, primarily based on electron‐rich cores, exhibit defects of high‐lying energy levels and inferior performance. We herein proposed a novel strategy by designing the benzothiazole‐fused cyanoindone (BTC) unit with ultra‐strong electron‐withdrawing ability as the terminal to synthesize the acceptor BTC‐2. The BTC unit imparts red‐shifted absorption up to 1000 nm to BTC‐2, attributed to enhanced intramolecular charge transfer and the quinoid resonance effect. Additionally, BTC‐2 features deep‐lying energy levels with the highest occupied molecular orbital level of −5.81 eV, due to the ultra‐strong electron‐withdrawing ability of BTC. Furthermore, BTC‐2 exhibits long‐range ordering in both molecular packing and macroscopic blend morphology, resulting from shoulder‐to‐shoulder packing of two BTC units, leading to an ultra‐long exciton lifetime over 1.1 ns. These superiorities facilitated a 17.17 % efficiency in the binary OPV device with an extremely high photocurrent of 30.34 mA cm−2, representing the best performance for ultra‐narrow bandgap electron acceptors, and a record light utilization efficiency of 4.88 % in binary semi‐transparent systems. Overall, BTC is a superior building block for designing ultra‐narrow bandgap electron acceptors.

Benzothiadiazole-Fused Cyanoindone: A Superior Building Block for Designing Ultra-Narrow Bandgap Electron Acceptor with Long-Range Ordered Stacking.

There are great demands of developing ultra-narrow bandgap electron acceptors for multifunctional electronic devices, particularly semi-transparent organic photovoltaics (OPVs) for building-integrated applications. However, current ultra-narrow bandgap materials applied in OPVs, primarily based on electron-rich cores, exhibit defects of high-lying energy levels and inferior performance. We herein proposed a novel strategy by designing the benzothiazole-fused cyanoindone (BTC) unit with ultra-strong electron-withdrawing ability as the terminal to synthesize the acceptor BTC-2. The BTC unit imparts red-shifted absorption up to 1000 nm to BTC-2, attributed to enhanced intramolecular charge transfer and the quinoid resonance effect. Additionally, BTC-2 features deep-lying energy levels with the highest occupied molecular orbital level of -5.81 eV, due to the ultra-strong electron-withdrawing ability of BTC. Furthermore, BTC-2 exhibits long-range ordering in both molecular packing and macroscopic blend morphology, resulting from shoulder-to-shoulder packing of two BTC units, leading to an ultra-long exciton lifetime over 1.1 ns. These superiorities facilitated a 17.17 % efficiency in the binary OPV device with an extremely high photocurrent of 30.34 mA cm-2, representing the best performance for ultra-narrow bandgap electron acceptors, and a record light utilization efficiency of 4.88 % in binary semi-transparent systems. Overall, BTC is a superior building block for designing ultra-narrow bandgap electron acceptors.

Interactions in GO/P3HT thin films: Spectroscopic investigation for organic solar cells

The present study was carried out to investigate the thin film properties of poly (3-hexylthiophene) (P3HT) coupled with graphene oxide (GO) using different spectroscopic techniques. The X-ray diffraction spectrum of GO/P3HT revealed a highly crystalline reflection of GO which is slightly shifted to higher diffraction angles as evidence of interaction with P3HT. Fourier transform infrared confirmed the alteration of P3HT structure upon interaction with GO by the increase in average conjugation length. The reflectance spectrum of GO/P3HT has an observable decrease in percentage reflectance, leading to an enhancement of light absorption. The fluorescent decay curves revealed a decline in exciton lifetime depicting quicker charge transfer, which decreased the exciton diffusion length. Our findings suggest that GO can be the hole transport material in organic solar cells.Graphical abstractSynthesis of GO/P3HT

Efficient Light-Driven Ion Pumping for Deep Desalination via the Vertical Gradient Protonation of Covalent Organic Framework Membranes.

Traditional desalination methods face criticism due to high energy requirements and inadequate trace ion removal, whereas natural light-driven ion pumps offer superior efficiency. Current synthetic systems are constrained by short exciton lifetimes, which limit their ability to generate sufficient electric fields for effective ion pumping. We introduce an innovative approach utilizing covalent-organic framework membranes that enhance light absorption and reduce charge recombination through vertical gradient protonation of imine linkages during acid-catalyzed liquid-liquid interfacial polymerization. This technique creates intralayer and interlayer heterojunctions, facilitating interlayer hybridization and establishing a robust built-in electric field under illumination. These improvements enable the membranes to achieve remarkable ion transport across extreme concentration gradients (2000:1), with a transport rate of approximately 3.2 × 1012 ions per second per square centimeter and reduce ion concentrations to parts per billion. This performance significantly surpasses that of conventional reverse osmosis systems, representing a major advancement in solar-powered desalination technology by substantially reducing energy consumption and secondary waste.

Transient dynamics and long-range transport of 2D exciton with managed potential disorder and phonon scattering

Two-dimensional excitons, characterized by high binding energy and valley pseudospin, are key to advancing photonic and electronic devices through controlled spatiotemporal dynamics of exciton flux. However, optimizing excitonic transport and emission dynamics, considering potential disorder and phonon scattering, requires further research. This study systematically investigates the effects of hexagonal boron nitride (hBN) encapsulation on semiconductor monolayers. Time-resolved photoluminescence (TRPL) and femtosecond pump-probe techniques reveal that encapsulation reduces excitonic radiative lifetime and enhances exciton-exciton annihilation, due to increased dielectric screening, which enlarges the Bohr radius and decreases binding energy. It also manages phonon scattering and thermal fluctuations, confirming non-monotonic temperature effects on emission and diffusion. The reduced disorder by hBN leads to a lowered optimized temperature from 250 K to 200 K, concurrently resulting in a doubled enhancement of the effective exciton diffusion coefficient. These findings highlight the importance of thermal and dielectric environmental control for ultrafast 2D exciton-based devices.

Benchmarking the integration of hexagonal boron nitride crystals and thin films into graphene-based van der Waals heterostructures

Abstract We present a benchmarking protocol that combines the characterization of boron nitride (BN) crystals and films with the evaluation of the electronic properties of graphene on these substrates. Our study includes hBN crystals grown under different conditions (atmospheric pressure high temperature, high pressure high temperature, pressure controlled furnace) and scalable BN films deposited by either chemical or physical vapor deposition (CVD or PVD). We explore the complete process from boron nitride growth, over its optical characterization by time-resolved cathodoluminescence (TRCL), to the optical and electronic characterization of graphene by Raman spectroscopy after encapsulation and Hall bar processing. Within our benchmarking protocol we achieve a homogeneous electronic performance within each Hall bar device through a fast and reproducible processing routine. We find that a free exciton lifetime of 1 ns measured on as-grown hBN crystals by TRCL is sufficient to achieve high graphene room temperature charge carrier mobilities of 80,000 cm2/(Vs) at a carrier density of |n| = 1×1012 cm−2, while respective exciton lifetimes around 100 ps yield mobilities up to 30,000 cm2/(Vs). For scalable PVD-grown BN films, we measure carrier mobilities exceeding 10,000 cm2/(Vs) which correlates with a graphene Raman 2D peak linewidth of 22 cm−1. Our work highlights the importance of the Raman 2D linewidth of graphene as a critical metric that effectively assesses the interface quality (i.e. surface roughness) to the BN substrate, which directly affects the charge carrier mobility of graphene. Graphene 2D linewidth analysis is suitable for all BN substrates and is particularly advantageous when TRCL or BN Raman spectroscopy cannot be applied to specific BN materials such as amorphous or thin films. This underlines the superior role of spatially-resolved spectroscopy in the evaluation of BN crystals and films for the use of high-mobility graphene devices.

Charge Transfer Donor-Acceptor Guests Confined within Metal-Organic Framework Crystals

Organic donor-acceptor (D-A) co-crystals have emerged as a promising class of semiconductors for photovoltaic applications.1,2 These co-crystals, which are packed through π-stacking interactions, can form charge transfer (CT) excitons within donor-acceptor pairs. These materials can exhibit unique and rare properties such as ambipolar charge transport, room-temperature ferroelectricity, and non-linear optical properties. Confinement of such D-A pairs within crystalline porous host materials such as metal-organic materials (MOFs)3 has rarely been studied. This approach can improve energy and charge transfer interactions by constraining their interaction and minimizing nonradiative energy transfer. Additionally, the formation of D-A pairs as dimers or a polymeric phase without altering the CT interactions can be controlled; band gap tunability is also possible. We hypothesize that confining D-A pairs within a porous network will also enhance the exciton lifetime compared to its dimer state in a crystal or in solution. In 2014, we reported an example of successful confinement of dihexyl-sexithiophene (acceptor) and [6,6]-phenyl-C61-butyric acid methyl ester (donor) molecules within the pores of MOF-177.4 In the present work, we focused on different sets of D-A pairs to provide direct structural insights, such as the location within the pore, host-guest interactions, and guest-guest orientation. For this purpose, we dissolved naphthalene-TCNQ or pyrene-TCNQ in dichloromethane (DCM) at a 1:1 ratio and soaked MOF-177 crystals in the solution for 3 days. UV-Vis spectroscopy reveals the difference in the absorption bands of the isolated molecules vs. D-A pairs in MOF pores. To confirm the presence of guest species inside the MOF and to determine the donor vs. acceptor ratio we obtained nuclear magnetic resonance (NMR) spectra. Interestingly, our preliminary results confirm that both naphthalene-TCNQ and pyrene-TCNQ pairs were accommodated inside the MOF but in different stoichiometric ratios. We also collected single crystal X-ray diffraction of the MOF crystals after being soaked after infiltration with D-A pairs. Structural refinement is underway to determine their position and interactions. Our approach provides new mechanistic insights and also produces new benchmark materials with long exciton lifetimes, which can be utilized to advance current photonic technologies. References Abou Taka, J. E. Reynolds Iii, N. C. Cole-Filipiak, M. Shivanna, C. J. Yu, P. L. Feng, et al. Phys. Chem. Chem. Phys. 2023, 25, 27065.Sun, Y. Wang, F. Yang, X. Zhang and W. Hu. Adv. Mater. 2019, 31, 1902328.Shivanna, Q.-Y. Yang, A. Bajpai, E. Patyk-Kazmierczak and M. J. Zaworotko, Nat. Commun. 2018, 9, 3080.K. Leong, M. E. Foster, B. M. Wong, E. D. Spoerke, D. Van Gough, J. C. Deaton, et al. J. Mat. Chem. A 2014, 2, 3389.

(Invited) Emerging Two-Dimensional Materials for Device Applications

Two-dimensional (2D) materials, such as Graphene, h-BN and MoS2, are promising candidates in a number of advanced device applications, owing to their exceptional electrical, optical and mechanical properties. Scalable growth of high quality 2D materials is crucial for their adoption in technological applications the same way the arrival of high-quality silicon single crystals was to the semiconductor industry. While CVD growth of wafer-scale monolayer graphene and TMDs has been demonstrated, considerable challenges still remain. In this talk, we first report a CVD method to grow fluorine rich 2D polymer (2DP-F) on varies substrates for low-k dielectrics in 2D TMDs based devices. Using precursors with low vaporize temperature, a uniform and ultra-flat 2DP-F film with controlled thickness can be deposited on silicon oxide wafer, glass, sapphire and mica substrates. Dielectric properties and relevant mechanical properties were carefully characterized. These 2DP-F films were then used as the substrate for transition metal dichalcogenides (TMDs) based devices, and significant improvements in device performances were found, possibly owing to the ultra-smooth and dangling bond free surface of 2DP-F that can significantly reduce the interfacial scattering of carriers.Next, we show that atomically thin Cs3Bi2I9, an all-inorganic lead-free perovskite derivative with strong optical activity can be successfully synthesized by vapor growth method. Reducing the dimensionality of such perovskites could utilize the materials’ advantages for solid-state information devices like valleytronics. By breaking the inversion symmetry, 2D Cs3Bi2I9 flakes with odd-layer number exhibited persistent, optically addressable valley polarization. This study potentially opens generalizable CVD method for growing a broad range of 2D perovskites towards cost-effective and energy-efficient integrated device applications. Finally, we report a two-step vapor phase growth process for the creation of high-quality vdW heterostructures based on perovskites and TMDCs, such as 2D Cs3Bi2I9/MoSe2, with a large lattice mismatch. Supported by experimental and theoretical investigations, we discover that the Cs3Bi2I9/MoSe2 vdW heterostructure possesses hybrid band alignments consisting of type-I and type-II heterojunctions because of the existence of defect energy levels in Cs3Bi2I9. More importantly, we demonstrate that the type-II heterojunction in the Cs3Bi2I9/MoSe2 vdW heterostructure not only shows a higher interlayer exciton density, but also exhibits a longer interlayer exciton lifetime than traditional 2D TMDCs based type-II heterostructures. Such vdW heterostructures provide promising platforms for exploring novel physics and cutting-edge optoelectronics and valleytronics applications.

Lead-Free All Inorganic Rubidium Copper Halide Rb2CuX3 (X = Cl, Br) for UVC Photodetector with Fast Response.

Recently, lead halide perovskites have shown great potential in the photodetection field. Unfortunately, the existence of toxic lead elements restricts their practical application. Herein, high-quality 1D lead-free crystals Rb2CuX3 (X = Cl, Br) are successfully synthesized in an acidic medium. Rb2CuCl3 and Rb2CuBr3 display violet photoluminescence emission peaks at 401 and 388nm with a high exciton lifetime of 12.78 and 59.67µs, respectively, which is due to self-trapped excitons (STE). Furthermore, a photodetector is fabricated to detect harmful UVC radiation with Rb2CuBr3 as a light absorber. The proposed photodetector has a responsivity of 0.92mAW-1 and a specific detectivity of 1.57 × 109 Jones with a fast response speed of 2.67/2.70 µs for rise/fall time, respectively. In addition, both the samples show good stability against open air, and continuous ultraviolet light (254nm), as well as good thermal stability which is necessary for device fabrication. Thus, the present study suggests that stable, non-toxic, and environment-friendly Rb2CuX3 (X = Cl, Br) can be a promising candidate for future UVC optoelectronic devices.

Photoinduced charge transfer and excitonic energy transfer in the CuInS2/ZnS/MoS2 heterotrilayer

Photo-induced charge transfer is the key process of many applications such as photovoltaics, photodetection, and light-emitting devices. With the outgrowth of a new class of low-dimensional semiconductors, i.e., monolayer transition metal dichalcogenides and semiconductor nanocrystals, charge transfer at the 2D/0D heterostructures has drawn many efforts because of the outstanding optical and electrical properties. This paper studies the dynamics of excitons of the CuInS2/ZnS/MoS2 heterotrilayer through femtosecond time-resolved transient absorption spectroscopy. The electron and hole transfer are observed by selectively exciting the electrons with tunable pump wavelengths. The exciton lifetimes are obtained on the picosecond scale. This work provides clues on exploring the non-toxic optoelectronic devices based on the CuInS2/ZnS/MoS2 heterotrilayer.

Low temperature exciton lifetime enhancement of MAPbBr3 studied by broadband terahertz spectroscopy

Over the past few years, lead halide perovskites have demonstrated significant potential in the field of solar cells, light-emitting diodes, and field-effect transistors. We investigated the transient photoconductivity and temperature-induced phase transitions in MAPbBr3 thin films, using ultrabroadband optical pump-terahertz probe spectroscopy with varying excitation fluences and temperature conditions. As the temperature drops from 293 to 123 K, MAPbBr3 undergoes two phase transitions, resulting in a significant extension of exciton lifetime in the tetragonal phase near 150 K, where MAPbBr3 exhibits a longer exciton lifetime. Our research contributes to a better understanding of the temperature-induced phase transition mechanism of MAPbBr3, enhancing its potential applications in optoelectronic devices.

Precise Regulation of the Reverse Intersystem Crossing Pathway by Hybridized Long‐Short Axis Strategy for High‐Performance Multi‐Resonance TADF Emitters

AbstractMulti‐resonance thermally activated delayed fluorescence (MR‐TADF) molecules have experienced great success in organic light‐emitting diodes (OLEDs) owing to their outstanding quantum efficiencies and narrow full width at half‐maximums (FWHMs). However, the reverse intersystem crossing (RISC) rates of MR‐TADF emitters are usually small, which will lead to relatively long triplet exciton lifetime and severe efficiency roll‐off. Here, we report an effective molecular design strategy to introduce multichannel RISC pathways and thus increase RISC rates without compromising the color fidelity and emission efficiency by the “hybridized long‐short axis (HLSA)” strategy. The TPA‐CN‐BN shows a near‐unity photoluminescence quantum yield, rapid RISC rate of 1.4×105 s−1, narrow FWHM of 23 nm, and small singlet‐triplet energy gap (ΔEST) of 0.06 eV in solution. The non‐sensitized OLED based on TPA‐CN‐BN exhibits a narrowband emission with the FWHM of 31 nm, in company with external quantum efficiency (EQE) of 37.9 %. Notably, the device exhibits the low efficiency roll‐off as the EQEs maintain 34.8 % and 21.8 % at 100 and 1000 cd m−2, respectively, representing the best performance for single‐host OLEDs based on the BCzBN skeleton. This study provides a fresh and promising approach to realize high‐performance OLEDs with high color purity and remarkable device efficiency.