Organic Optoelectronic Materials Research Articles

End-to-End Bent Perylene Bisimide Cyclophanes by Double Sulfur Extrusion.

Bending inherently planar π-cores consisting of only six-membered rings has traditionally been challenging because a powerful transformation is required to compensate for the significant strain energy associated with bending. Herein, we demonstrate that sulfur extrusion can achieve substantial molecular bending of a perylene structure to form a substructure of a Vögtle belt, a proposed yet hitherto elusive carbon nanotube fragment. Bent perylene bisimide (PBI) derivatives were synthesized through a double-sulfur-extrusion reaction from the corresponding sulfur-containing V-shaped precursors with an internal alkyl tether. The effect of bending the inherently planar PBI core, which is a recent topic of interest for the design of advanced organic electronic and optoelectronic materials, was investigated systematically. Increasing the curvature leads to a red shift in the absorption and emission spectra, while the fluorescence quantum yields remain high. This stands in contrast with the nonemissive features of previously reported nonplanar PBI derivatives based on conjugative tethers. Detailed photophysical measurements indicated that the increasing curvature with shorter alkyl tethers (i) slightly facilitates intersystem crossing and (ii) significantly suppresses the internal conversion in the excited state of the present bent PBI derivatives. The latter characteristics originate from the restricted dynamic motion associated with the charge-transfer (CT) character between the core chromophores and the N-aryl units.

Large Language Model-Based AI Agent for Organic Semiconductor Devices Research.

Large language models (LLMs) have attracted widespread attention recently, however, their application in specialized scientific fields still requires deep adaptation. In this work, we designed an artificial intelligence (AI) agent for organic field effect transistors (OFETs) by integrating the GPT-4 model with well-trained machine learning (ML) algorithms. It can efficiently extract the experimental parameters of OFETs from scientific literature and reshape them into a structured database, achieving precision and recall rates both exceeding 92%. Combined with well-trained ML models, this AI agent can further provide targeted guidance and suggestions for device design. With prompt engineering and human-in-loop strategies, the agent extracted sufficient information of 709 OFETs from 277 research articles across different publishers and gathered them into a standardized database containing more than 10000 device parameters. Using this database, we trained a ML model based on XGBoost for device performance judgment. Combined with the interpretation of the high-precision model, the agent has provided a feasible optimization scheme that has tripled the charge transport properties of DP-DTT OFETs. Our work is an effective practice of LLMs in the field of organic optoelectronic devices and expands the research paradigm of organic optoelectronic materials and devices. This article is protected by copyright. All rights reserved.

A Chlorinated Indolium‐Based Nonlinear Optical Crystal Achieving Effective Terahertz‐Wave Generation and Highly Sensitive Detection

AbstractNonlinear optical (NLO) crystals have shown great potential in generating and detecting coherent terahertz waves, which have a wide range of applications. However, designing the microscopic structure of NLO crystals to obtain excellent macroscopic properties has been a challenge. In this work, by the introduction of chloro substitution into the cation part of indolium‐based salt structure, a new acentric OH5CI‐BS crystal, namely, [(C19H19NOCl)+∙(C6H5SO3)−, P1] is synthesized and grown using a feasible evaporation method. The cut‐off edge of the grown OH5CI‐BS crystal reaches 524 nm, corresponding to a bandgap of 2.37 eV. The largest single crystals of OH5CI‐BS with the size of ≈ 9 × 8 × 0.3 mm3 are grown. Remarkably, by use of OH5CI‐BS crystals as both the THz‐wave emitter and detector, a widely tunable (from 2.23 to 33.54 THz) and monochromatic THz system is demonstrated for the first time, and the detection depth of the OH5CI‐BS based up‐conversion at room temperature is >4 orders better than a commercial Golay Cell and even 2 orders better than a 4‐K‐Bolometer. This work indicates that OH5CI‐BS is a promising future NLO material for terahertz technology, and also provides a feasible design strategy for other organic optoelectronic functional materials.

A Heteronuclear W/Cu/S Clusters‐Based Donor–Acceptor Polymer for Perovskite Solar Cells

AbstractDonor–acceptor polymers containing the repeating moiety of electron‐rich unit (donor) and electron‐deficient group (acceptor), impair their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) considerably localized on the donors and acceptors, respectively. Their band gaps can be well‐tuned by the electron‐donating ability of donors and the electron‐withdrawing ability of acceptors. The efficient splitting of photo‐generated excitons by electronic pull–push effect between donor and acceptor could promote the effective charge transport within polymer. Therefore, donor–acceptor polymers have the merits of versatile molecule structure, accessible functionalization, and adjustable electronic structure, becoming one of the most promising organic optoelectronic materials. For instance, by adjusting the alternating array of donor and acceptor moieties, a series of donor–acceptor polymers with lower band gaps and good light‐harvesting ability are prepared and used as potential photoelectronic materials.

Exploring Efficient Dual-Phase Emissive Fluorophores with High Mobility by Integrating a Rigid Donor and Flexible Acceptor.

Developing luminogens with a high emission efficiency in both single-molecule and aggregate states, as well as high mobility, shows promise for advancing the iteration and update of organic optoelectronic materials. However, achieving a delicate balance between the plane configuration of luminophores and the strong exciton interactions of aggregates is a formidable task from the molecular design perspective. This dilemma was overcome by integrating a rigid donor and flexible acceptor to establish donor-acceptor (D-A) type emitters. The π-conjugate-extended donor ensures the substantial planarity of these molecules, allowing strong emission in solution with photoluminescence quantum yield values of 86% and 75%. Furthermore, the restricted molecular motion of the aggregation-induced emission moiety and the formation of J-aggregates reduce the quenching effect, leading to a high emissive efficiency of 85% and 91% in the aggregate state. The mildly distorted D-A geometry builds moderate electrostatic interaction, resulting in high mobility with μM,h of 7.12 × 10-5 and 3.27 × 10-4 cm2/V s. Additionally, an improved synthesized procedure for terminal E-configured acrylonitrile with metal-free and concise reaction conditions is presented. The successful application of the synthesized compounds in organic light-emitting diode devices demonstrates the practicability of the molecular design strategy with connecting a rigid donor and flexible acceptor.

Vacuum‐free lamination via controlled polymer adhesion for selective photogeneration and photodetection

AbstractThis study attempts to develop a reproducible thin‐film formation technique called vacuum‐free (VF) lamination, which transfers thin films using elastomeric polymer‐based laminating mediators. Precisely, by controlling the interface characteristics of the mediator based on the work of adhesion, VF lamination is successfully performed for various thicknesses (from 20 to 240 nm) of a conjugated photoactive material composed of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐bʹ]dithiophene))‐alt‐(5,5‐(1ʹ,3ʹ‐di‐2‐thienyl‐5ʹ,7ʹ‐bis(2‐ethylhexyl)benzo[1ʹ,2ʹ‐c:4ʹ,5ʹ‐cʹ]dithiophene‐4,8‐dione)] (a polymer donor) and 2,2ʹ‐((2Z,2ʹZ)‐((12,13‐bis(2‐butyloctyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2ʹʹ,3ʹʹ:4ʹ,5ʹ]thieno[2ʹ,3ʹ:4,5]pyrrolo[3,2‐g]thieno[2ʹ,3ʹ:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (a nonfullerene acceptor). Interestingly, the organic photovoltaic and photodetecting applications, prepared by the VF lamination process, showed superior performance compared to those of devices prepared by conventional spin‐coating. This is due to the overturned surface morphology, which led to enhanced charge transport ability and blocking of the externally injected charge. Thus, the reproducible VF lamination process, exploiting an adhesion‐based elastomeric polymer mediator, is a promising thin‐film formation technique for developing efficient next‐generation organic optoelectronic materials consistent with the solution process.

Organic near-infrared optoelectronic materials and devices: an overview

Organic near-infrared optoelectronic materials and devices: an overview

Discovery of Organic Optoelectronic Materials Powered by Oxidative Ar-H/Ar-H Coupling.

Efficient and streamlined synthetic methods that facilitate the rapid build-up of structurally diverse π-conjugated systems are of paramount importance in the quest for organic optoelectronic materials. Among these methods, transition-metal-catalyzed oxidative Ar-H/Ar-H coupling reactions between two (hetero)arenes have emerged as a concise and effective approach for generating a wide array of bi(hetero)aryl and fused heteroaryl structures. This innovative approach bypasses challenges associated with substrate pre-activation processes, thereby allowing for the creation of frameworks that were previously beyond reach using conventional Ar-X/Ar-M coupling reactions. These inherent advantages have ushered in new design patterns for organic optoelectronic molecules that deviate from traditional methods. This ground-breaking approach enables the transcendence of the limitations of repetitive material structures, ultimately leading to the discovery of novel high-performance materials. In this Perspective, we provide an overview of recent advances in the development of organic optoelectronic materials through the utilization of transition-metal-catalyzed oxidative Ar-H/Ar-H coupling reactions. We introduce several notable synthetic strategies in this domain, covering both directed and non-directed oxidative Ar-H/Ar-H coupling strategies, dual chelation-assisted strategy and directed ortho-C-H arylation/cyclization strategy. Additionally, we shed light on the role of oxidative Ar-H/Ar-H coupling reactions in the advancement of high-performance organic optoelectronic materials. Finally, we discuss the current limitations of existing protocols and offer insights into the future prospects for this field.

Influence of molecular structure on the coupling strength to a plasmonic nanoparticle and hot carrier generation.

Strong coupling between metal nanoparticles and molecules mixes their excitations, creating new eigenstates with modified properties such as altered chemical reactivity, different relaxation pathways or modified phase transitions. Here, we explore excited state plasmon-molecule coupling and discuss how strong coupling together with a changed orientation and number of an asymmetric molecule affects the generation of hot carriers in the system. We used a promising plasmonic material, magnesium, for the nanoparticle and coupled it with CPDT molecules, which are used in organic optoelectronic materials for organic electronic applications due to their facile modification, electron-rich structure, low band gap, high electrical conductivity and good charge transport properties. By employing computational quantum electronic tools we demonstrate the existence of a strong coupling mediated charge transfer plasmon whose direction, magnitude, and spectral position can be tuned. We find that the orientation of CPDT changes the nanoparticle-molecule gap for which maximum charge separation occurs, while larger gaps result in trapping hot carriers within the moieties due to weaker interactions. This research highlights the potential for tuning hot carrier generation in strongly coupled plasmon-molecule systems for enhanced energy generation or excited state chemistry.

Machine-learning-assisted performance improvements for multi-resonance thermally activated delayed fluorescence molecules.

With favorable colour purity, multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules exhibit enormous potential in high-definition displays. Due to the relatively small chemical space of MR-TADF molecules, it is challenging to improve molecular performance through domain-specific expertise alone. To address this problem, we focused on optimizing the classic molecule, DABNA-1, using machine learning (ML). Molecular morphing operations were initially employed to generate the adjacent chemical space of DABNA-1. Subsequently, a machine learning model was trained with a limited database and used to predict the properties throughout the generated chemical space. It was confirmed that the top 100 molecules suggested by machine learning present excellent electronic structures, characterized by small reorganization energy and singlet-triplet energy gaps. Our results indicate that the improvement in electronic structures can be elucidated through the view of the molecular orbital (MO). The results also reveal that the top 5 molecules present weaker vibronic peaks of the emission spectrum, demonstrating higher colour purity when compared to DABNA-1. Notably, the M2 molecule presents a high RISC rate, indicating its promising future as a high-efficiency MR-TADF molecule. Our machine-learning-assisted approach facilitates the rapid optimization of classical molecules, addressing a crucial requirement within the organic optoelectronic materials community.

Preparation of Carbazoles Involving 6π-Electrocyclization, Photoredox-, Electrochemical-, and Thermal Cyclization Reactions: Mechanistic Insights.

Carbazole is a heterocyclic motif that can be found in a diverse array of natural and unnatural products displaying a wide range of biological and physiological properties. Furthermore, this heterocycle is part of electronic materials like photoconducting polymers and organic optoelectronic materials owing to its excellent photophysical characteristics. Consequently, the development of synthetic strategies for carbazole scaffolds holds potential significance in biological and material fields. In this regard, a variety of preparation methods has been developed to exploit their efficient and distinct formation of new C-C and C-heteroatom bonds under mild conditions and enabling broad substrate diversity and functional group tolerance. Therefore, this review focuses on the synthesis of a set of carbazole derivatives describing a variety of methodologies that involve direct irradiation, photosensitization, photoredox, electrochemical and thermal cyclization reactions.

Organic Optoelectronic Materials: A Rising Star of Bioimaging and Phototherapy.

Recently, many organic optoelectronic materials (OOMs), especially those used in organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs), are explored for biomedical applications including imaging and photoexcited therapies. In this review,recently developed OOMs for fluorescence imaging, photoacoustic imaging, photothermal therapy, and photodynamic therapy, are summarized. Relationships between their molecular structures, nanoaggregation structures, photophysical mechanisms, and properties for various biomedical applications are discussed. Mainly four kinds of OOMs are covered: thermally activated delayed fluorescence materials in OLEDs, conjugated small molecules and polymers in OSCs, and charge-transfer complexes in OFETs. Based on the OOMs unique optical properties, including excitation light wavelength and exciton dynamics, they are respectively exploited for suitable biomedical applications. This review is intended to serve as a bridge between researchers in the area of organic optoelectronic devices and those in the area of biomedical applications. Moreover, it provides guidance for selecting or modifying OOMs for high-performance biomedical uses. Current challenges and future perspectives of OOMs are also discussed with the hope of inspiring further development of OOMs for efficient biomedical applications.

Double boron–oxygen-fused polycyclic aromatic hydrocarbons: skeletal editing and applications as organic optoelectronic materials

An efficient one-pot strategy for the facile synthesis of double boron–oxygen-fused polycyclic aromatic hydrocarbons (dBO-PAHs) with high regioselectivity and efficient skeletal editing is developed. The boron–oxygen-fused rings exhibit low aromaticity, endowing the polycyclic aromatic hydrocarbons with high chemical and thermal stabilities. The incorporation of the boron–oxygen units enables the polycyclic aromatic hydrocarbons to show single-component, low-temperature ultralong afterglow of up to 20 s. Moreover, the boron–oxygen-fused polycyclic aromatic hydrocarbons can also serve as ideal n-type host materials for high-brightness and high-efficiency deep-blue OLEDs; compared to single host, devices using boron–oxygen-fused polycyclic aromatic hydrocarbons-based co-hosts exhibit dramatically brightness and efficiency enhancements with significantly reduced efficiency roll-offs; device 9 demonstrates a high color-purity (Commission International de l’Eclairage CIEy = 0.104), and also achieves a record-high external quantum efficiency (28.0%) among Pt(II)-based deep-blue OLEDs with Commission International de l’Eclairage CIEy < 0.20; device 10 achieves a maximum brightnessof 27219 cd/m2 with a peak external quantum efficiency of 27.8%, which representes the record-high maximum brightness among Pt(II)-based deep-blue OLEDs. This work demonstrates the great potential of the double boron–oxygen-fused polycyclic aromatic hydrocarbons as ultralong afterglow and n-type host materials in optoelectronic applications.

Synthesis of Organic Optoelectronic Materials Using Direct C-H Functionalization.

Small molecules and polymers with conjugated structures can be used as organic optoelectronic materials. These molecules have conventionally been synthesized by cross-coupling reactions; however, in recent years, direct functionalization of C-H bonds has been used to synthesize organic optoelectronic materials. Representative reactions include direct arylation reactions (C-H/C-X couplings, with X being halogen or pseudo-halogen) and cross-dehydrogenative coupling (C-H/C-H cross-coupling) reactions. Although these reactions are convenient for short-step synthesis, they require regioselectivity in the C-H bonds and suppression of undesired homo-coupling side reactions. This review introduces examples of the synthesis of organic optoelectronic materials using two types of direct C-H functionalization reactions. In addition, we summarize our recent activities in the development of direct C-H functionalization reactions using fluorobenzenes as substrates. This review covers the reaction mechanism and material properties of the resulting products.

Efficient screening framework for organic solar cells with deep learning and ensemble learning

Organic photovoltaics have attracted worldwide interest due to their unique advantages in developing low-cost, lightweight, and flexible power sources. Functional molecular design and synthesis have been put forward to accelerate the discovery of ideal organic semiconductors. However, it is extremely expensive to conduct experimental screening of the wide organic compound space. Here we develop a framework by combining a deep learning model (graph neural network) and an ensemble learning model (Light Gradient Boosting Machine), which enables rapid and accurate screening of organic photovoltaic molecules. This framework establishes the relationship between molecular structure, molecular properties, and device efficiency. Our framework evaluates the chemical structure of the organic photovoltaic molecules directly and accurately. Since it does not involve density functional theory calculations, it makes fast predictions. The reliability of our framework is verified with data from previous reports and our newly synthesized organic molecules. Our work provides an efficient method for developing new organic optoelectronic materials.

Towards Artificial Visual Sensory System: Organic Optoelectronic Synaptic Materials and Devices

AbstractDeveloping an artificial visual sensory system requires optoelectronic materials and devices that can mimic the behavior of biological synapses. Organic/polymeric semiconductors have emerged as promising candidates for optoelectronic synapses due to their tunable optoelectronic properties, mechanic flexibility, and biological compatibility. In this review, we discuss the recent progress in organic optoelectronic synaptic materials and devices, including their design principles, working mechanisms, and applications. We also highlight the challenges and opportunities in this field and provide insights into potential applications of these materials and devices in next‐generation artificial visual systems. By leveraging the advances in organic optoelectronic materials and devices, we can envision its future development in artificial intelligence.

Towards Artificial Visual Sensory System: Organic Optoelectronic Synaptic Materials and Devices.

Developing an artificial visual sensory system requires optoelectronic materials and devices that can mimic the behavior of biological synapses. Organic/polymeric semiconductors have emerged as promising candidates for optoelectronic synapses due to their tunable optoelectronic properties, mechanic flexibility, and biological compatibility. In this review, we discuss the recent progress in organic optoelectronic synaptic materials and devices, including their design principles, working mechanisms, and applications. We also highlight the challenges and opportunities in this field and provide insights into potential applications of these materials and devices in next-generation artificial visual systems. By leveraging the advances in organic optoelectronic materials and devices, we can envision its future development in artificial intelligence.

Sulfone/Carbonyl-Based Donor-Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging.

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Thermal annealing promoted room temperature phosphorescence: motion models and internal mechanism.

Thermal annealing has been proven to be an efficient method to optimize the device performance of organic and polymeric opto-electronic materials. However, no detailed information of aggregate structures was obtained for a deeper understanding of what happens during thermal annealing. Herein, through modulation of molecular configurations by tunable linkage positions, and the amplified amplitudes of molecular motions by incorporation of additional methylene units, accurate changes of aggregated structures upon thermal annealing have been achieved, accompanying with the 'turn-on' room temperature phosphorescence (RTP) response by about 4800- and 177-fold increase of lifetimes. The stretching and swing motion models have been proposed, which afforded an efficient way to investigate the science of dynamic aggregation in depth.

Multi‐Hydrogen Bonds Enhanced Anchoring Effect Enabling High‐Efficiency Blue Phosphorescence, Single‐Molecule White Light, and Tunable Colorful Emission with Quantitative Energy Transfer

AbstractUltralong organic room‐temperature phosphorescence (RTP) materials, especially high‐energy blue emission materials, have attracted tremendous attention but remain difficult to achieve. Here, a strategy based on the multi‐hydrogen bonds enhanced anchoring effect is developed to activate single‐molecule blue phosphorescence emission with the highest efficiency of 29.79%. Specifically, the aromatic electrophilic directing (AED) effect provides a rational explanation for the structural spectral change. The construction of artificial light‐harvesting systems via physical blending achieves on‐demand modulation for afterglow color, including white afterglow. Furthermore, cold‐white emission is also achieved via a structural π‐extension optimization strategy. Moreover, the high transmittance and reversible water‐sensitivity render these polymer films with applicability as smart organic optoelectronic materials.