Donor Acceptor Research Articles

Precisely regulation of photochromism via absorption-induced photoreaction attenuation and light intensity dependence for time-resolved asymmetric encryption

With the growing need for secure information storage, encryption materials are required to be designed with high information capacity, easy to prepare, and hard to decode. Here, donor–acceptor Stenhouse adducts (DASAs), known for their straightforward synthesis, are used to develop a new time-resolved asymmetric encryption strategy, enhancing information capacity. The photoswitching property of DASAs is regulated by the intensity of initial absorbance and the intensity of light irritation. Besides, we recognize the relationship between the intensity of initial absorbance and photoswitching rate constant is caused by the absorption-induced photoreaction attenuation (AIPA). By rationally regulating the photo-bleching time of DASAs, the information can be sequentially revealed (colored state) or concealed (bleached state) in the desired temporal order. As a result, a quick response (QR) code label for practical application and a multi-level encoding scheme for sophisticated asymmetric encryption have been proposed. Specifically, the advanced asymmetric encryption technique employs layer sequence and light intensity as private keys, diverging from traditional public key systems. Information is sequentially displayed over time. The accurate information can only be revealed at the correct temporal dimension (layer sequence) and the appropriate decoding parameter (light intensity), both of which are precisely controlled by AIPA. This study not only unveils an approach to time-resolved asymmetric encryption using DASAs, enhancing the security and capacity of information storage, but also paves the way for the development of high-security encryption materials that are both highly efficient and resistant to unauthorized decoding efforts.

Hydrogen-bonded organic framework for fire-safe epoxy composite with photochromic properties and rapid de-icing capability

Multifunctionalized epoxy resin (EP) composites are essential for advancing technological innovation across various applications. One efficient method to achieve this is through the development of multifunctional EP fillers. In this work, 2,4,6-tri(pyridin-4-yl)pyridine (Tripp) as electron acceptor and phosphoric acid as electron donor are self-assembled to form a donor–acceptor (D-A) type hydrogen-bonded organic framework (HOF, named P-HOF) using a solvent volatilization method. P-HOF exhibits excellent photochromic and photothermal properties under 365 nm UV irradiation. Electron paramagnetic resonance (EPR) analysis confirms the generation of viologen radicals, and the internal electron transfer mechanism of P-HOF is further elucidated using X-ray photoelectron spectroscopy (XPS). Furthermore, incorporating 3 wt% P-HOF into EP as a filler results in an EP/P-HOF composite that not only retains excellent photochromic and photothermal properties but also demonstrates rapid de-icing and outstanding flame retardancy. The EP/P-HOF coating demonstrates a de-icing efficiency that is 3.83 times higher than that of pure EP coatings. Compared to pure EP, the EP/P-HOF significantly reduced the peak heat release rate (pHRR), total heat release (THR), and peak smoke production rate (pSPR) by 55.0 %, 19.6 %, and 29.6 %, respectively.

Molecular-Scale Interactions in the Choline Chloride-Ethylene Glycol Deep Eutectic Solvent System: The Importance of Chromophore Charge in Mediating Rotational Dynamics.

We report on the rotational diffusion dynamics of three chromophores (disodium fluorescein, oxazine 725, and perylene) in a series of choline chloride-ethylene glycol (ChCl:EG) deep eutectic solvent (DES) systems. We observe behavior independent of DES bulk viscosity for the cationic and neutral probes and behavior that is consistent with stick-limit interactions for the modified Debye-Stokes-Einstein model for the anionic probe. This finding indicates that the anionic species is integral to the interactions between DES constituent species that are responsible for local organization, consistent with previous MD simulations that showed higher interaction energies associated with both the hydrogen bond donor (EG) and hydrogen bond acceptor (Ch+) interactions with Cl- in ChCl:EG mixtures. The reorientation data reported here also indicate a region around 15 mol % ChCl where the stoichiometric relationship between the species gives rise to changes in the details of intermolecular interactions.

Synthesis of Quinone‐Amine‐Linked Covalent Organic Frameworks for Boosting the Photocatalytic Removal of Uranium

AbstractCompared to imine covalent organic frameworks (COFs), the superior stability of amine‐linked COFs renders them more suitable for long‐term harsh real‐world environments. Their numerous amine sites can serve as functional groups or be subjected to post‐modification to further enhance the performance of the material. However, the assortment and abundance of amine‐linked COFs via currently lacking due to restricted monomer varieties and synthetic methods. Herein, this study presents an innovative approach for synthesizing quinone‐amine‐linked COFs by directly combining 2,5‐dihydroxy‐1,4‐benzoquinone (DHBQ) with various amine monomers and introduce a novel photocatalyst, DHBQ‐TAPP‐COF, specifically tailored to efficiently reduce uranium in harsh environments. DHBQ‐TAPP‐COF features a unique donor–acceptor structure, with the DHBQ units serving as acceptors because they contain abundant oxygen atoms that facilitate metal ion coordination, thereby enhancing charge carrier separation, carrier utilization, and uranium reduction efficiency. The quinone‐amine linkages offer improved stability, extended π‐conjugation, heightened local polarity, and conductivity, which enable efficient carrier transfer within the material and thus enhance the overall performance of the uranium photocatalyst. The proposed photocatalyst can efficiently reduce U(VI) without sacrificial agents or decomposition to precipitate UO2 at a recovery rate exceeding 98%. This catalyst provides an efficient and convenient strategy for the stable and high‐performance photocatalytic reduction of uranium.

Facilitating Charge Separation of Donor–Acceptor Conjugated Microporous Polymers via Position Isomerism Strategy for Efficient CO2 Photoconversion

Photoreduction of CO2 into the chemical feedstocks of fuels provides a green way to help solve both the energy crisis and carbon emission issues. Nevertheless, undesirable charge separation and migration, as well as rapid reverse charge recombination results in the unsatisfactory photocatalytic activity of most conjugated microporous polymers (CMPs). Herein, a pair of donor–acceptor (D-A) CMPs for CO2 photoconversion was developed through position isomerism by altering linkage sites. The results show that Py-D27F with 2,7-site linkage exhibits a completely conjugated structure and a large molecular dipole moment, thus significantly accelerating charge separation and transfer. As a result, Py-D27F achieves a higher yield of 320.9 μmol g−1 h−1 for CO2-to-CO photoreduction (without the addition of any photosensitizers and precious metals), which is about three-fold greater than that of Py-D36F (3,6-site linkage). This study provides a valuable idea for exploring outstanding CMP photocatalysts for the efficient processing of photocatalysis.

High‐Efficiency Near‐Infrared Iridium(III) Complexes with Tailored Ligands for Solution‐Processed OLEDs with Maximum EQE of 3.75% at 830 nm

AbstractThe development of highly efficient pure near‐infrared (NIR) emitting organic materials with emission beyond 800 nm is extremely challenging due to the limitation of the energy gap law. Herein, three efficient NIR emitting iridium(III) complexes are developed adopting pyrido[3,4‐b]pyrazine derivatives as the cyclometalated C^N ligands, namely (Epptt)2Iracac (1), (pptt)2Iracac (2), and (ppCz)2Irtmd (3). Due to the enhanced donor–acceptor interaction inside the ligand, the conjugation‐extended and electron‐richer N‐phenylcarbazole unit at the C‐part of the ligands endows complex 3 with a large bathochromic shift of emission peak from 796 to 862 nm in toluene solution, compared with thieno[3,2‐b]thiophene C‐part in complex 2. The solution‐processed OLEDs based on complex 3 achieved a record high maximum external quantum efficiency of 3.75% and low efficiency roll‐off with the emission peak at 830 nm, a champion efficiency in the Ir(III) based OLEDs with emission peak exceeding 800 nm. This work opens a new avenue for the development of high‐efficiency pure NIR organic emitters based on Ir(III) complexes for various applications.

High‐Performance, Single‐Component Ambipolar Organic Electrochemical Transistors with Balanced n/p‐Type Properties for Inverter and Biosensor Applications

AbstractAmbipolar organic electrochemical transistors (OECTs) with a single organic mixed ionic‐electronic conductor (OMIEC) have unique advantages by reducing fabrication complexity and cost in complementary logic circuit and bioelectronic applications. However, the design and synthesis of high‐performance ambipolar OMIECs for efficient transport and coupling both cation/anion and electron/hole remain challenging. Herein, a donor–acceptor (D–A)‐typed ambipolar OMIEC polymer (DHF‐gTT) is presented, whose superior ambipolarity stems from the concurrent oligoethyleneglycol‐functionalized D/A units that facilitates cation/anion injection and transport. Additionally, the fluorination of acceptor unit improves both hole/electron transports due to the fully‐locked backbone and promotes electron injection by down‐shifting molecular energy levels. Consequently, DHF‐gTT‐based OECTs achieve balanced figure‐of‐merit (µC*) for both p‐type and n‐type operations (12.4–14.6 F cm−1 V−1 s−1), setting new benchmarks for ambipolar OECTs, in terms of n‐type µC* and electron/hole mobilities. Such ambipolar OECTs enable the inverter to achieve a record‐high gain (102 V/V) and associated n‐type and p‐type molecular detectors to offer real‐time and highly sensitive detection of histamine and hydrogen peroxide detection, respectively. These results indicate the effectiveness of judicious molecular design on achieving high‐performance ambipolar OMIECs, allowing the state‐of‐the‐art single‐component ambipolar OECTs for both highly integrated logic circuit and bioelectronic applications.

2D sp2 carbon-linked benzotrithiophene covalent organic frameworks for selective sulfoxidation with oxygen driven by green light

Covalent organic frameworks (COFs) are promising photocatalysts with excellent chemical stability, broad light absorption, and tailorable molecular structures. To assemble highly crystalline 2D (two-dimensional) COFs, planar molecular units like benzotrithiophene (BTT) and 2,2′-bipyridine (Bpy) are highly desired. Herein, two COFs are assembled by the condensation of benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene-2,5,8-tricarbaldehyde with [2,2′-bipyridine]-5,5′-diacetonitrile and [2,2′-bipyridine]-5,5′-diamine, respectively. An sp2 carbon-linked COF Bpy-sp2c-BTT-COF and an imine-linked COF Bpy-IM-BTT-COF with apparent electron donor–acceptor configuration are readily furnished in which the planarity of Bpy underpins their crystallinity. The sp2-carbon linkage is more essential than the imine linkage in adjusting band structure and facilitating electron transfer over Bpy-sp2c-BTT-COF and Bpy-IM-BTT-COF. Therefore, Bpy-sp2c-BTT-COF demonstrates better performance than Bpy-IM-BTT-COF for selective sulfoxidation with oxygen driven by green light in which superoxide and single oxygen are both involved during the activation of oxygen. The linkage selection for COFs opens new doors into visible light photocatalysts for selective conversions.

Dual-donor D-A-D types electrochromic conjugated polymers employed quinoxaline as the acceptor: Synthesis, electrochemistry, and electrochromism

In this work, two donor-acceptor-donor (D-A-D) type electrochromic conjugated polymers were prepared upon electrochemical oxidation through their precursors employed dual-thiophene derivatives as the donor units and quinoxaline as the acceptor unit. The effects of different donor substituents on the polymers’ electrochemical and electrochromic properties were carefully examined. Owing to the introduction of stronger electron donor ability of 3,4-ethylenedioxythiophene (EDOT), P(Q-T-E) demonstrated good coplanarity and dense surface morphology, outstanding redox activity and stability (retained 97 % after 1000 cycles), low optical band gap (1.45 eV). P(Q-T-T) exhibited excellent electrochromic performance of above 30 % transmittance changes in both the NIR region and the visible region, as fast as 0.75 s response time, and high coloration efficiency value of 212.8 cm2 C−1. The Dual-donor strategy may provide a new research idea to achieve high-performance electrochromic D-A-D conjugated polymers.

Synergistically Improved Crystallinity and Molecular Doping Ability of Polythiophene-Diketopyrropyrrole Derivatives by m-Trifluoromethylbenzene Containing Side Chains for Improved Thermoelectric Materials.

m-Trifluoromethylbenzene (FB) groups have been widely employed in various fields; however, no studies have reported the use of FB in side chains to enhance the carrier mobility and molecular doping of conjugated polymers. In this study, based on density functional theory (DFT) calculations, we discovered that FB groups can effectively bind to [FeCl4]-, the counterion of the p-type dopant FeCl3, thereby increasing doping ability. Consequently, FB groups were incorporated into the side chains of thiophene-diketopyrrolopyrrole-based donor-acceptor (D-A)-conjugated polymers, and a series of random conjugated polymers were synthesized (denoted as PDPPFB-x, where x represents the molar ratio of the FB side chain). The findings revealed that an appropriate number of FB groups can decrease the π-π stacking distances, enhance the films' crystallinity, and consequently improve the charge transfer ability. Furthermore, after doping with FeCl3, the UV-vis-NIR spectra indicated that the doping efficiency was augmented by increasing the molar fraction of the FB side chain. Among these polymers, PDPPFB-10 exhibited the highest conductivity and power factor, which were 2.0 and 1.5 times higher than those of PDPPFB-0, respectively. These results illustrated a straightforward molecular design strategy for enhancing the crystallinity and conductivity of conjugated polymers, thereby expanding the way to optimize their thermoelectric performance.

Donor-only substituted benzene achieves thermally activated delayed fluorescence

Thermally activated delayed fluorescence (TADF) is a promising mechanism for harvesting triplet excitons in organic light-emitting diodes (OLEDs). The donor–acceptor (D–A) design is the most conventional strategy for developing efficient TADF emitters. A subsequently emerged approach, known as the multiple resonance (MR) effect, also employs electron-donating and electron-withdrawing functional groups. Thus, developing TADF materials has traditionally relied on ingenuity in selecting and combining two functional units. Here, we have realized a TADF molecule by utilizing only a carbazole donor moiety. This molecule is an unusual example in the family of TADF materials and offers better insight into the electronic structures in the excited states for luminescent materials.

Design and numerical investigation of Cs2SnI6 vacancy-ordered double perovskite solar cell

Perovskite solar cells (PSCs) represent an emerging technology in solar photovoltaics due to their outstanding optical and electrical characteristics. The urgency of lead-free solar materials has increased due to the environmental concerns. In light of these considerations, Cs2SnI6, a high-performance tin-based double perovskite, holds the potential to be a key absorber material in promoting the cell efficiency. In this paper, a device design of lead-free Cs2SnI6-based PSC is proposed based on an n-i-p planar structure. Through a comprehensive analysis by simulation using SCAPS-1D, the impacts of electron transport layer materials (SnO2, TiO2, CdS, GO, MZO) and hole transport layer materials (MoO3, Cu2O, CuI, Spiro-OMeTAD) with varying thicknesses as well as the donor density, acceptor density and the absorber thickness have been examined. Additionally, an examination is conducted on the performance metrics of PSCs, encompassing Voc, Jsc, FF, and PCE, while taking into consideration the influences of temperature, Rseries, and Rshunt. The results show that the optimized FTO/SnO2/Cs2SnI6/MoO3/Au device presents the highest PCE of 22.60 % at 300 K temperature, together with a visible quantum efficiency of 99.49 %. The appropriate thicknesses of the ETL, HTL, and absorber layer for achieving the optimal performances are 50 nm, 200 nm, and 450 nm, respectively. Also, the donor density and acceptor density for the best efficiency are both at 1018 cm−3. The values of Rseries, and Rshunt are 2 Ω cm2 and 6000 Ω cm2, respectively. This investigation demonstrates that the proposed vacancy-ordered double perovskite Cs2SnI6 solar cell is promising for photovoltaic devices due to the highlighted characteristics and optical parameters.

Synergistic charge-transfer dynamics of novel D-D-A-π-A framework containing indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers: from structural engineering to performance metrics in photovoltaic solar cells.

Dye-sensitized solar cells (DSSCs) present a convincing substitute for conventional silicon-based solar cells because of their possible lower manufacturing costs and versatile uses. Electron injection and dye regeneration processes are important in meeting the need for photosensitizers with improved efficiency and stability. Aimed at enhancing the performance and efficiency of DSSCs, this study focuses on the structural engineering to performance metrics of novel indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers (LHZ1 to LHZ9) with D-D-A-π-A framework. The current study provides insights into the photovoltaic and optoelectronic properties of the investigated dyes, which are significantly influenced by the modification of auxiliary donors (D), internal acceptors with thiophene as a spacer, and cyanoacrylic acid (A) as the terminal acceptor. These modifications enhance rapid charge transfer among the dyes, highlighting the critical role of dye-semiconductor interactions. The suitability of developed sensitizers for DSSCs applications is confirmed by executing quantum methods like NBO, TDM, FMO, DOS, Eb, ΔGreg, ΔGinject, VRP, and ICT parameters qCT (e-), DCT ( ), H index ( ), ∆( ), t index ( ), and μCT (D). All of the investigated dyes have HOMO levels lower than the electrode I-/I3-'s redox potential (-4.8 eV) and LUMO values that are appropriately higher than the conduction band of TiO2 (-4.0 eV). The novel dyes showed a closing of the energy gap (2.38-1.84 eV). The LHZ7 and LHZ8 molecules with the lowest Eg (1.97 eV and 1.84 eV) demonstrated the highest absorption (up to 746 nm > 402 nm for LHZ), which was caused by the insertion effect of varied donors and internal acceptors. Almost all photosensitizers appeared with remarkable properties, i.e., red-shifted absorption maxima (746 nm), lowest Ex (1.66 eV), Eb (0.02 eV), and highest values of LHE (0.958). The TDM analysis revealed high charge density on HOMO of donor and LUMO of acceptors in designed dyes. DOS analysis revealed that the donor parts of the molecules delocalized the highest occupied molecular orbitals of dye particles. The electronic properties predicted by the NBO analysis showed that donor groups donate high and faster transfer of charge, and internal acceptor groups rapidly accept them. The electron injection (ΔGinject) and dye regeneration (ΔGreg) analysis of photosensitizers attached with TiO2 proved efficient charge transfer properties from the donor of newly designed dyes onto the conduction band of TiO2. This study, also supported by the thermodynamic stability of dyes with negative values of Gibbs free energy, revealed that the performance of the designed dyes is augmented by modifying the donor and internal acceptors of the reference photosensitizer for effective application in the experimental community. All of the dyes are suitable for DSSCs based on the calculated parameters. Still, the LHZ9 dye proved proficient in applying dye-sensitized solar cells due to its remarkable properties, i.e., lowest gap and red-shifted absorption maxima.

3-Methylthiophene: A Sustainable Solvent for High-Performance Organic Solar Cells.

The use of harmful halogenated or aromatic solvents such as chloroform (CF), chlorobenzene (CB), and o-xylene (o-XY) is one of the greatest barriers to the industrial-scale manufacturing of high-performance organic solar cells (OSCs). Therefore, it is necessary to eliminate the effects of these solvents to ensure practical feasibility of OSCs. We found that the anthracene-terminated polymer donor and small-molecule acceptor BO-4Cl had good solubility in 3-methylthiophene (3-MeT). There were no toxicity labels in the SDS and exposure control limits for 3-MeT. An overall power conversion efficiency of 16.87% was achieved by using 3-MeT as the solvent for solar cell fabrication, which was higher than that of the cells made from CF (16.18%) and o-XY (15.69%). The best OSC based on PM6:D18:L8-BO and fabricated with 3-MeT exhibited a high PCE of 18.13%, which is one of the highest values for cells fabricated from halogen-free solvents. These results indicate that 3-MeT is an eco-friendly and low-toxicity solvent for the sustainable fabrication of the OSC active layer.

Enhancing Donor–Acceptor Interaction and Framework Stability by the Povarov Reaction for Photocatalytic H2O2 Production

Enhancing Donor–Acceptor Interaction and Framework Stability by the Povarov Reaction for Photocatalytic H₂O₂ Production

Four compounds containing 1-(2-carboxyethyl)-4,4′-bipyridine: Synthesis, crystal structure and chromic behavior

Herein, four compounds containing the neutral viologen derivative, 1-(2-carboxyethyl)-4,4′-bipyridine (CBbpy) have been synthesized, (CBbpy)·(H2TPDC)·H2O (1), [Co0.5(CBbpy)(H2O)2](HTPDC)·2 H2O (2), [Ni0.5(CBbpy)(H2O)2](HTPDC)·2 H2O (3) and {[Cd(CBbpy)2(H2O)2][Cd(TPDC)2]·4 H2O}n (4) (H2TPDC = thiophene-2,5-dicarboxylic acid). Compound 1 is a co-crystal that forms the donor-acceptor (D-A) system through non-covalent interactions. Compounds 2 and 3 own the same isolated structure, in which metal ions coordinate with CBbpy to form cations, while H2TPDC loses a proton to form anions. Compound 4 contains one-dimensional (1D) {[Cd(CBbpy)2(H2O)2]2+}n double chain and two-dimensional (2D) {[Cd(TPDC)2]2-}n layer, which leads to a 1D + 2D→three-dimensional (3D) interdigitated supramolecular architecture. Although four compounds comprise the same bipyridinium moiety, their chromic behaviors are different. Compounds 1 and 4 own reversible photochromic action, while 2 and 3 reveal hydrochromic action upon heating. Based on the photochromic properties of 1 and 4, the photo-modulated fluorescence and the potential applications of inkless and erasable printing are investigated.

Nitroxide Spin Labels for Exploring Relationships Between Molecular Structure, Microenvironment and EPR Parameters: A Mini-review Dedicated to Carlo Corvaja

AbstractThis mini-review is dedicated to Carlo Corvaja (University of Padova) in recognition of his important contributions to the study of biomimetic donor–acceptor model dyads and triads and to the understanding of spin exchange in excited fullerene–nitroxide derivatives. We report on attractive examples of multi-frequency and multi-resonance EPR spectroscopy, highlighting recent work in Padova and Berlin/Mülheim. The examples selected include TR-EPR, ENDOR, and EDNMR experiments on photoexcited spin-labeled macromolecules, such as fullerene–nitroxide complexes or photosynthetic bacterial reaction centers, which were optionally NO spin-labeled. From the spin interaction parameters measured, detailed information about structure and dynamics of macromolecules embedded in liquid-solution or solid-state microenvironments could be extracted.

A Water‐Soluble Fluorescent Probe Derived from Pyridine‐2,6‐Dicarboxylic Acid: Synthesis, Interaction with Ions, and Two‐Photon Microscopy

AbstractTwo‐photon excited fluorescence is a process in which the excited fluorophore relaxes and emits fluorescence after two‐photon absorption. Combined with appropriate two‐photon fluorescent probes, two‐photon microscopy enables observation deep inside tissue without damage. Former reports showed that the two‐photon absorption cross sections of donor–acceptor (D–A) dipoles, as well as D‐π‐D and D–A–D quadrupoles can be strengthened by using strong D–A groups. In this study, a novel water‐soluble fluorescent probe with D‐π‐A structure containing pyridine‐2,6‐dicarboxylic acid unit was synthesized. The maximum excitation wavelength and emission wavelength of the probe in aqueous solution were 328 nm and 471 nm, respectively. The fluorescence emitted by the probe can be quenched by various metal cations. The pyridyl N and carboxyl O in the probe formed chelates with Cu2+, which resulted in a fluorescence quenching response, and showed a linear relationship between fluorescent intensity and Cu2+ concentration with wide linear range and low limit of detection. CCK‐8 tests showed the probe had no obvious toxicity to 4T1 cells in the range of 0.4–50 μmol L−1, and the cell survival rate was above 86 %. The probe had a large two‐photon absorption cross section ranging from 680 nm to 820 nm. The two‐photon absorption cross section reached 100 GM at 760 nm of excitation wavelength. By means of microscopic imaging of 4T1 cells stained with the probe, one‐photon fluorescence represented blue emission, while two‐photon fluorescence represented bright green emission. The probe was proved to have good cell permeability, and preferred to target nucleus, showing application potential in two‐photon fluorescence imaging technology.

The ab initio study of n-type nitrogen and gallium co-doped diamond

Abstract In order to better understand the influence of different complexes on the diamond co-doping system, N and Ga are chosen as co-dopants in diamond. The properties of several substitutional NmGan (m+n <= 3) complexes with vacancy (Va) in the bulk diamond have been investigated by ab initio density functional technique, including their optimized lattice structures, formation energies, binding energies and thermodynamic transition levels. The calculational results show that NmGan complexes in the donor-acceptor-donor (DAD) configuration can provide ionization energies similar to phosphorus-doped diamond. All other complexes provide deep impurity levels. For the DAD configuration, the adsorption process on the diamond surface has been studied to demonstrate the feasibility of growing diamonds containing N-Ga-N in experiments. The desired complex configuration is not uniquely present in the co-doped system. Investigating these properties of different complexes beyond NGaN provides insight into the N and Ga codoped diamond system, yielding a more comprehensive understanding of its potential and limitations. Our research ideas can also be extended to other co-doped systems and help to evaluate other potential co-dopants for diamond.

Hybrid Local and Charge Transfer Emitters Utilizing Hyperconjugation Effect Towards Solution-Processed Ultra-Deep-Blue OLEDs with External Quantum Efficiency Approaching 12.

Hybrid local and charge transfer (HLCT) excited state materials, which possess weak donor-acceptor (D-A) pure organic structures, deserve one of the most promising efficient and stable blue emitters. Through high-lying reverse intersystem crossing (hRISC) process, 75% triplet excitons generated by electrical excitation could be harvested and utilized in organic light-emitting diodes (OLEDs). However, there are still significant challenges to achieve high-efficiency ultra-deep-blue HLCT emitters with low Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinate y values. Here, a series of novel blue HLCT emitters based on spiro[1,8-diazafluorene-9,2'-imidazole] structure were designed and synthesized by fine-tuning the spiro[fluorene-9,2'-imidazole] core structure in our previous work through heteroatom substitution and hyperconjugation effect. The target emitters were endowed with excellent photophysical and electrochemical merits, thermal stability and solution processibility. The solution-processed OLED device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[1,8-diazafluorene-9,2'-imidazole] (NFIP-CZ) achieved efficient ultra-deep-blue emission (CIEx,y = 0.1581, 0.0422) with the maximum external quantum efficiency (EQEmax), maximum current efficiency (CEmax) and maximum power efficiency (PEmax) of 11.94%, 4.07 cd·A-1 and 2.56 lm·W-1. The record EQE is a breakthrough in both solution-processed and vacuum vapor deposition ultra-deep-blue HLCT-OLEDs currently.