Fine-Tuning of Crystal Packing and Charge Transport Properties of BDOPV Derivatives through Fluorine Substitution

Effect of Halogen Substituents on Charge Transport Properties of n-type Organic Semiconductors: A Theoretical Study

Organic semiconductors (OSCs) have received significant attention as promising materials for electronic devices. In this study, we investigate the impact of halogen groups on the charge transport properties of n-type OSC-6,13 bis((triisopropylsilyl)ethynyl)-5,7,12,14-tetraazapentacene (TIPS-TAP). The computed mobilities for TIPS-TAPs substituted with F and Cl exhibit excellent agreement with the experimental values, while the simulation overestimates the electron mobility for TIPS-TAP. Interestingly, the mobility of TIPS-TAP-4F is significantly lower than that of TIPS-TAP-4Cl/Br, despite their similar packing structures. This discrepancy can be attributed to the strong electron-withdrawing effect of fluoride, which reduces the electron transfer integral and increases the reorganization energy. While molecular packing is widely recognized as a dominant factor in charge transport in OSCs, our study highlights the crucial role of electronic effects in charge transport in OSCs. This study provides new insights into the mechanisms underlying charge transport in OSCs.

Sensitive SWIR Organic Photodetectors with Spectral Response Reaching 1.5 µm

The performance of organic photodetectors (OPDs) sensitive to the short-wavelength infrared (SWIR) light lags behind commercial indium gallium arsenide (InGaAs) photodetectors primarily due to the scarcity of organic semiconductors with efficient photoelectric responses exceeding 1.3 µm. Limited by the Energy-gap law, ultralow-bandgap organic semiconductors usually suffer from severe non-radiative transitions, resulting in low external quantum efficiency (EQE). Herein, a difluoro-substituted quinoid terminal group (QC-2F) with exceptionally strong electron-negativity is developed for constructing a new non-fullerene acceptor (NFA), Y-QC4F with an ultralow bandgap of 0.83 eV. This subtle structural modification significantly enhances intermolecular packing order and density, enabling an absorption onset up to 1.5 µm while suppressing non-radiation recombination in Y-QC4F films. SWIR OPDs based on Y-QC4F achieve an impressive detectivity (D*) over 1011 Jones from 0.4 to 1.5 µm under 0 V bias, with a maximum of 1.68 × 1012 Jones at 1.16 µm. Furthermore, the resulting OPDs demonstrate competitive performance with commercial photodetectors for high-quality SWIR imaging even under 1.4 µm irradiation.

Optimizing Double-Fibril Network Morphology via Solid Additive Strategy Enables Binary All-Polymer Solar Cells with 19.50% Efficiency

Double-fibril network morphology (DFNM), in which the donor and the acceptor can self-assemble into a double-fibril structure, is beneficial for exciton dissociation and charge transport in organic solar cells. Herein, it is demonstrated that such DFNM can be constructed and optimized in all-polymer solar cells (all-PSCs) with the assistance of 2-alkoxynaphthalene volatile solid additives. It is revealed that the incorporation of 2-alkoxynaphthalene can induce a stepwise regulation in the aggregation of donor and acceptor molecules during film casting and thermal annealing processes. Through altering the alkoxy of 2-alkoxynaphthalene solid additives, both the intermolecular interactions and molecular miscibility with the host materials can be precisely tuned, which allows for the optimization of the molecular aggregation process and facilitation of molecular self-assembly, and thus leading to reinforced molecular packing and optimized DFNM. As a result, an unprecedented efficiency of 19.50% (certified as 19.1%) is obtained for 2-ethoxynaphthalene-processed PM6:PY-DT-X all-PSCs with excellent photostability (T80 = 1750 h). This work reveals that the optimization of DFNM via solid additive strategy is a promising avenue to boosting the performance of all-PSCs.

1,2,3,4-Tetrafluorobiphenylene: A Prototype Janus-Headed Scaffold for Ambipolar Materials

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses. The crystal structure features head-to-tail π-stacking and other fluorine-related secondary bonding interactions. From the nucleus-independent chemical shifts descriptor, the four-membered ring of the title compound is antiaromatic, and the six-membered rings are aromatic. The Janus molecule is highly polarized; and the six-membered fluoro- and hydrocarbon rings are Lewis π-acidic and π-basic, respectively. The electrochemically-generated radical cation of the title compound is long-lived as characterized by electron paramagnetic resonance, whereas the radical anion is unstable in solution. The title compound reveals electrical properties of an insulator. On expanding its molecular scaffold towards partially fluorinated [n]phenylenes (n≥2), the properties presumably can be transformed into those of semiconductors. In this context, the title compound is suggested as a prototype scaffold for ambipolar materials for organic electronics and spintronics.

Functionalized Phenanthrene Imide-Based Polymers for n-Type Organic Thin-Film Transistors

High-performing n-type polymers are crucial for the advance of organic electronics field, however strong electron-deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide-functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π-conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high-performance n-type polymers. Among the PAHs, phenanthrene (PhA) features a well-delocalized aromatic π-system with multiple modifiable active sites . However, the PhA-based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene-modified CPCNI exhibits a well stabilized LUMO energy level (-3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI, two polymers PCPOI-Tz and PCPCNI-Tz were developed. Applied to organic thin-film transistors, owing to the strong electron-deficiency of CPCNI, polymer PCPCNI-Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI-Tz. This work affords two structurally novel electron-deficient building blocks and highlights the effectiveness of dual functionalization of PhAs with strong electron-withdrawing groups for devising n-type polymers.

Tuning Shortwave-Infrared J-aggregates of Aromatic Ring-Fused Aza-BODIPYs by Peripheral Substituents for Combined Photothermal and Photodynamic Therapies at Ultralow Laser Power

Achieving photothermal therapy (PTT) at ultralow laser power density is crucial for minimizing photo-damage and allowing for higher maximum permissible skin exposure. However, this requires photothermal agents to possess not just superior photothermal conversion efficiency (PCE), but also exceptional near-infrared (NIR) absorptivity. J-aggregates, exhibit a significant redshift and narrower absorption peak with a higher extinction coefficient. Nevertheless, achieving predictable J-aggregates through molecular design remains a challenge. In this study, we successfully induced desirable J-aggregation (λabs max : 968 nm, ϵ: 2.96×105  M-1  cm-1 , λem max : 972 nm, ΦFL : 6.2 %) by tuning electrostatic interactions between π-conjugated molecular planes through manipulating molecular surface electrostatic potential of aromatic ring-fused aza-BODIPY dyes. Notably, by controlling the preparation method for encapsulating dyes into F-127 polymer, we were able to selectively generate H-/J-aggregates, respectively. Furthermore, the J-aggregates exhibited two controllable morphologies: nanospheres and nanowires. Importantly, the shortwave-infrared J-aggregated nanoparticles with impressive PCE of 72.9 % effectively destroyed cancer cells and mice-tumors at an ultralow power density of 0.27 W cm-2 (915 nm). This phototherapeutic nano-platform, which generates predictable J-aggregation behavior, and can controllably form J-/H-aggregates and selectable J-aggregate morphology, is a valuable paradigm for developing photothermal agents for tumor-treatment at ultralow laser power density.

A Chirally Locked Bis-perylene Diimide Macrocycle: Consequences for Chiral Self-Assembly and Circularly Polarized Luminescence

Macrocycles containing chiral organic dyes are highly valuable for the development of supramolecular circularly polarized luminescent (CPL) materials, where a preorganized chiral framework is conducive to directing π-π self-assembly and delivering a strong and persistent CPL signal. Here, perylene diimides (PDIs) are an excellent choice for the organic dye component because, alongside their tunable photophysical and self-assembly properties, functionalization of the PDI's core yields a twisted, chiral π-system, capable of CPL. However, configurationally stable PDI-based macrocycles are rare, and those that are also capable of π-π self-assembly beyond dimers are unprecedented, both of which are advantageous for robust self-assembled chiroptical materials. In this work, we report the first bay-connected bis-PDI macrocycle that is configurationally stable (ΔG⧧ > 155 kJ mol-1). We use this chirally locked macrocycle to uncover new knowledge of chiral PDI self-assembly and to perform new quantitative CPL imaging of the resulting single-crystal materials. As such, we discover that the chirality of a 1,7-disubstituted PDI provides a rational route to designing H-, J- and concomitant H- and J-type self-assembled materials, important arrangements for optimizing (chir)optical and charge/energy transport properties. Indeed, we reveal that CPL is amplified in the single crystals of our chiral macrocycle by quantifying the degree of emitted light circular polarization from such materials for the first time using CPL-Laser Scanning Confocal Microscopy.

Morphology Control for Efficient Nonfused Acceptor-Based Organic Photovoltaic Cells

Non-fused electron acceptors have huge advantages in fabricating low-cost organic photovoltaic (OPV) cells. However, morphology control is a challenge as non-fused C─C single bonds bring more molecular conformations. Here, by selecting two typical polymer donors, PBDB-TF and PBQx-TF, the blend morphologies and its impacts on the power conversion efficiencies (PCEs) of non-fused acceptor-based OPV cells are studied. A selenium-containing non-fused acceptor named ASe-5 is designed. The results suggest that PBQx-TF has a lower miscibility with ASe-5 when compared with PBDB-TF. Additionally, the polymer networks may form earlier in the PBQx-TF:ASe-5 blend film due to stronger preaggregation performance, leading to a more obvious phase separation. The PBQx-TF:ASe-5 blend film shows faster charge transfer and suppressed charge recombination. As a result, the PBQx-TF:ASe-5-based device records a good PCE of 14.7% with a higher fill factor (FF) of 0.744, while the PBDB-TF:ASe-5-based device only obtains a moderate PCE of 12.3% with a relatively low FF of 0.662. The work demonstrates that the selection of donors plays a crucial role in controlling the blend morphology and thus improving the PCEs of non-fused acceptor-based OPV cells.

Porous Complex-Mediated Dual Emission of Porphyrins for the Electrochemiluminescence Bioassay

Although porphyrins make up a promising class of electrochemiluminescence (ECL) luminophors, their aggregation-caused quenching (ACQ) characteristics lead to inferior ECL efficiency (ΦECL). Furthermore, current application of porphyrins is limited to cathodic emission. This work creatively exploited a cage-like porous complex (referred to as SWU-1) as the microreactor to recede the ACQ effect while modulating dual ECL emission of meso-tetra(4-carboxyphenyl)porphine (TCPP), which self-assembled with SWU-1 to form TCPP@SWU-1 nanocapsules (TCPP@SWU-1 NCs). As the microreactor, SWU-1 not only effectively constrained TCPP aggregation to improve electron-hole recombination efficiency but also improved stability of anion and cation radicals, thus significantly enhancing the dual emission of TCPP. Compared with TCPP aggregates, the resulting TCPP@SWU-1 NCs exhibited significantly enhanced anodic and cathodic emission, and their ΦECL was increased by 8.7-fold and 3.9-fold, respectively. Furthermore, black hole quencher-2 (BHQ2) can simultaneously quench anodic and cathodic signals. TCPP@SWU-1 NCs coupling BHQ2 conveniently achieved an ECL ratio detection of miRNA-126, and the limit of detection (S/N = 3) was 4.1 aM. This work pioneered the development of the cage-like porous complex SWU-1 as the microreactor to alleviate defects of the ACQ effect and mediate dual emission of TCPP. The coupling of dual-emitting TCPP@SWU-1 NCs and dual-function moderator BHQ2 created a novel single-luminophor-based ratio system for bioanalysis and provided a promising ECL analysis approach for miRNA-126.

Enhanced Photothermal Property of NDI-Based Conjugated Polymers by Copolymerization with a Thiadiazolobenzotriazole Unit

Solar steam generation (SSG) is a promising photothermal technology to solve the global water storage issue. The potential of π-conjugated polymers as photothermal materials is significant, because their absorption range can be customized through molecular design. In this study, naphthalenediimide (NDI) and thiadiazolobenzotriazole (TBZ) were employed as bifunctional monomers to produce conjugated polymers. There are two types of polymers, P1 and P2. P1 is based on NDI, while P2 is a copolymer of NDI and TBZ in a ratio of 9:1. Both polymers had high molecular weights and sufficient thermal stability. UV-vis-near-infrared (NIR) absorption spectra revealed that both polymers have large extinction coefficients ascribed to the NDI and TBZ chromophores. Notably, the absorption spectrum of P2 exhibited a significant red shift compared to P1, resulting in a narrow optical bandgap and absorption in the NIR range. This result suggested that P2 has a higher light absorption than P1. Photoluminescence (PL) spectra were measured to elucidate the conversion of the absorbed light into thermal energy. It was found that P2 has a reduced fluorescence quantum yield as a result of the TBZ unit, signifying a proficient conversion of the photothermal energy. Based on the results, it appears that the P2 film has a greater photothermal property compared to that of the P1 film. The surface temperature of the P2 film reached approximately 50 °C under the investigated conditions. In addition, copolymer P2 exhibited an impressive SSG efficiency of 72.4% under 1 sun (1000 W/m2) irradiation. All the results suggested that narrow bandgap conjugated polymers containing the TBZ unit are highly effective materials for achieving optimal performance in SSGs.

Aldol Condensation for the Construction of Organic Functional Materials

Aldol condensation is a cost-effective and sustainable synthetic method, offering the advantages of low complexity, substrate universality, and high efficiency. Over the past decade, it has become popular for creating next-generation organic functional materials, particularly rigid-rod conjugated (semi)conductors. This review focuses on conjugated small molecules, oligomers, and polymeric (semi)conductors synthesized through aldol condensation, with emphasis on their remarkable features in advancing n-type organic field-effect transistors (OFETs), organic electrochemical transistors (OECTs), organic photovoltaics (OPVs), and organic thermoelectrics (OTEs) as well as NIR-II photothermal conversion. Coherence character, optical properties, microstructure, and chain conformation are investigated to understand material-property relationships. Future applications and challenges in this area are also discussed.

Molecular Design Concept for Enhancement Charge Carrier Mobility in OFETs: A Review

In the last two decades, organic field-effect transistors (OFETs) have garnered increasing attention from the scientific and industrial communities. The performance of OFETs can be evaluated based on three factors: the charge transport mobility (μ), threshold voltage (Vth), and current on/off ratio (Ion/off). To enhance μ, numerous studies have concentrated on optimizing charge transport within the semiconductor layer. These efforts include: (i) extending π-conjugation, enhancing molecular planarity, and optimizing donor-acceptor structures to improve charge transport within individual molecules; and (ii) promoting strong aggregation, achieving well-ordered structures, and reducing molecular distances to enhance charge transport between molecules. In order to obtain a high charge transport mobility, the charge injection from the electrodes into the semiconductor layer is also important. Since a suitable frontier molecular orbitals' level could align with the work function of the electrodes, in turn forming an Ohmic contact at the interface. OFETs are classified into p-type (hole transport), n-type (electron transport), and ambipolar-type (both hole and electron transport) based on their charge transport characteristics. As of now, the majority of reported conjugated materials are of the p-type semiconductor category, with research on n-type or ambipolar conjugated materials lagging significantly behind. This review introduces the molecular design concept for enhancing charge carrier mobility, addressing both within the semiconductor layer and charge injection aspects. Additionally, the process of designing or converting the semiconductor type is summarized. Lastly, this review discusses potential trends in evolution and challenges and provides an outlook; the ultimate objective is to outline a theoretical framework for designing high-performance organic semiconductors that can advance the development of OFET applications.

An In-Situ Cyanidation Strategy To Access Tetracyanodiacenaphthoanthracene Diimides with High Electron Mobilities Exceeding 10 cm2 V-1 s-1

A family of novel highly π-extended tetracyano-substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four-fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π-conjugated backbone with the in-situ formation of four cyano substitutents at room temperature while avoiding extra cyano-functionalization reactions. TCDADIs decorated with different N-alkyl substituents present good solubility, near-coplanar backbones, good crystallinity, and low-lying lowest unoccupied molecular orbital energies of -4.33 eV, all of which contribute to desirable electron-transport performance when applied in organic field-effect transistors (OFET). The highest electron mobility of an OFET based on a 2-hexyldecyl-substituted TCDADI single crystal reaches 12.6 cm2  V-1  s-1 , which is not only among the highest values for the reported n-type organic semiconductor materials (OSMs) but also exceeds that of most n-type OSMs decorated with imide units.

Insights into the kinetics and self-assembly order of small-molecule organic semiconductor/quantum dot blends during blade coating

Organic-inorganic nanocomposite films formed from blends of small-molecule organic semiconductors and colloidal quantum dots are attractive candidates for high efficiency, low-cost solar energy harvesting devices. Understanding and controlling the self-assembly of the resulting organic-inorganic nanocomposite films is crucial in optimising device performance, not only at a lab-scale but for large-scale, high-throughput printing and coating methods. Here, in situ grazing incidence X-ray scattering (GIXS) gives direct insights into how small-molecule organic semiconductors and colloidal quantum dots self-assemble during blade coating. Results show that for two blends separated only by a small difference in the structure of the small molecule forming the organic phase, crystallisation may proceed down two distinct routes. It either occurs spontaneously or is mediated by the formation of quantum dot aggregates. Irrespective of the initial crystallisation route, the small-molecule crystallisation acts to exclude the quantum dot inclusions from the growing crystalline matrix phase. These results provide important fundamental understanding of structure formation in nanocomposite films of organic small molecules and colloidal quantum dots prepared via solution processing routes. It highlights the fundamental difference to structural evolution which can be made by seemingly small changes in system composition. It provides routes for the structural design and optimisation of solution-processed nanocomposites that are compatible with the large-scale deposition manufacturing techniques that are crucial in driving their wider adoption in energy harvesting applications.

Aza-Cibalackrot: Turning on Singlet Fission Through Crystal Engineering

Singlet fission is a photophysical process that provides a pathway for more efficient harvesting of solar energy in photovoltaic devices. The design of singlet fission candidates is non-trivial and requires careful optimization of two key criteria: (1) correct energetic alignment and (2) appropriate intermolecular coupling. Meanwhile, this optimization must not come at the cost of molecular stability or feasibility for device applications. Cibalackrot is a historic and stable organic dye which, although it has been suggested to have ideal energetics, does not undergo singlet fission due to large interchromophore distances, as suggested by single crystal analysis. Thus, while the energetic alignment is satisfactory, the molecule does not have the desired intermolecular coupling. Herein, we improve this characteristic through molecular engineering with the first synthesis of an aza-cibalackrot and show, using ultrafast transient spectroscopy, that singlet fission is successfully "turned on."

Mixed Small-Molecule Matrices Improve Nanoparticle Dispersibility in Organic Semiconductor-Nanoparticle Films

Controlling the dispersibility of nanocrystalline inorganic quantum dots (QDs) within organic semiconductor (OSC):QD nanocomposite films is critical for a wide range of optoelectronic devices. This work demonstrates how small changes to the OSC host molecule can have a dramatic detrimental effect on QD dispersibility within the host organic semiconductor matrix as quantified by grazing incidence X-ray scattering. It is commonplace to modify QD surface chemistry to enhance QD dispersibility within an OSC host. Here, an alternative route toward optimizing QD dispersibilities is demonstrated, which dramatically improves QD dispersibilities through blending two different OSCs to form a fully mixed OSC matrix phase.

Tuning the Solid Phase Fluorescence Emission from Long Wavelength Visible to Near-Infrared in Oxazol-5-One Derivatives: Structure-Property Relationship, Theoretical and Experimental Studies

Most of the fluorescent molecules among organic [Formula: see text]-conjugated materials show blue or green emission in the solid phase but few of them emit red-shifted visible and near-infrared light in the material science. To create molecules emitting for this feature, two π-conjugated oxazol-5-one derivatives containing donor (OCH₃) and acceptor groups (NO₂) were synthesized. Their optical and charge-transport properties were investigated through experimental and theoretical methods including the single crystal X-ray crystallography, Hirshfeld Surface Analysis, photophysical studies and Density Functional Theory (DFT), respectively. In addition, FT-IR, ¹H-NMR, ¹³C-NMR spectroscopy, cyclic voltammetry (CV) measurements were performed. According to our results, both molecules may provide the significant pathway of development of long wavelength visible and red emissive features in solid phase with the aggregation induced enhanced emission (AIEE) properties particularly in the fields of OLEDs, optical communication, defence and bioimaging.

Backbone coplanarity manipulation via hydrogen bonding to boost the n-type performance of polymeric mixed conductors operating in aqueous electrolyte

The development of high-performance n-type semiconducting polymers remains a significant challenge. Reported here is the construction of a coplanar backbone via intramolecular hydrogen bonds to dramatically enhance the performance of n-type polymeric mixed conductors operating in aqueous electrolyte. Specifically, glycolated naphthalene tetracarboxylicdiimide (gNDI) couples with vinylene and thiophene to give gNDI-V and gNDI-T, respectively. The hydrogen bonding functionalities are fused to the backbone to ensure a more coplanar backbone and much tighter π-π stacking of gNDI-V than gNDI-T, which is evidenced by density functional theory simulations and grazing-incidence wide-angle X-ray scattering. Importantly, these copolymers are fabricated as the active layer of the aqueous-based electrochromic devices and organic electrochemical transistors (OECTs). gNDI-V exhibits a larger electrochromic contrast (ΔT = 30%) and a higher coloration efficiency (1988 cm² C^-1) than gNDI-T owing to its more efficient ionic-electronic coupling. Moreover, gNDI-V gives the highest electron mobility (0.014 cm² V^-1 s^-1) and μC* (2.31 FV^-1 cm^-1 s^-1) reported to date for NDI-based copolymers in OECTs, attributed to the improved thin-film crystallinity and molecular packing promoted by hydrogen bonds. Overall, this work marks a remarkable advance in the n-type polymeric mixed conductors and the hydrogen bond functionalization strategy opens up an avenue to access desirable performance metrics for aqueous-based electrochemical devices.

Semiconducting Polymer Nanoparticles with Surface-Mimicking Protein Secondary Structure as Lysosome-Targeting Chimaeras for Self-Synergistic Cancer Immunotherapy

Immunotherapy has received tremendous attention for tumor treatment, but the efficacy is greatly hindered by insufficient tumor-infiltration of immune cells and immunosuppressive tumor microenvironment. The strategy that can efficiently activate cytotoxic T lymphocytes and inhibit negative immune regulators will greatly amplify immunotherapy outcome, which is however very rare. Herein, a new kind of semiconducting polymer (SP) nanoparticles is developed, featured with surface-mimicking protein secondary structure (SPSS NPs) for self-synergistic cancer immunotherapy by combining immunogenic cell death (ICD) and immune checkpoint blockade therapy. The SPs with excellent photodynamic property are synthesized by rational fluorination, which can massively induce ICD. Additionally, the peptide antagonists are introduced and self-assembled into β-sheet protein secondary structures on the photodynamic NP surface via preparation process optimization, which function as efficient lysosome-targeting chimaeras (LYTACs) to mediate the degradation of programmed cell death ligand-1 (PD-L1) in lysosome. In vivo experiments demonstrate that SPSS NPs can not only elicit strong antitumor immunity to suppress both primary tumor and distant tumor, but also evoke long-term immunological memory against tumor rechallenge. This work introduces a new kind of robust immunotherapy agents by combining well-designed photosensitizer-based ICD induction and protein secondary structures-mediated LYTAC-like multivalence PD-L1 blockade, rendering great promise for synergistic immunotherapy.

The COMPAS Project: A Computational Database of Polycyclic Aromatic Systems. Phase 1: cata-Condensed Polybenzenoid Hydrocarbons

Chemical databases are an essential tool for data-driven investigation of structure-property relationships and for the design of novel functional compounds. We introduce the first phase of the COMPAS Project─a COMputational database of Polycyclic Aromatic Systems. In this phase, we developed two data sets containing the optimized ground-state structures and a selection of molecular properties of ∼34k and ∼9k cata-condensed polybenzenoid hydrocarbons (at the GFN2-xTB and B3LYP-D3BJ/def2-SVP levels, respectively) and placed them in the public domain. Herein, we describe the process of the data set generation, detail the information available within the data sets, and show the fundamental features of the generated data. We analyze the correlation between the two types of computations as well as the structure-property relationships of the calculated species. The data and insights gained from them can inform rational design of novel functional aromatic molecules for use in, e.g., organic electronics, and can provide a basis for additional data-driven machine- and deep-learning studies in chemistry.

Electrochemical Deposition of a Single-Crystalline Nanorod Polycyclic Aromatic Hydrocarbon Film with Efficient Charge and Exciton Transport

Electrochemical deposition has emerged as an efficient technique for preparing conjugated polymer films on electrodes. However, this method encounters difficulties in synthesizing crystalline products and controlling their orientation on electrodes. Here we report electrochemical film deposition of a large polycyclic aromatic hydrocarbon. The film is composed of single-crystalline nanorods, in which the molecules adopt a cofacial stacking arrangement along the π-π direction. Film thickness and crystal size can be controlled by electrochemical conditions such as scan rate and electrolyte species, while the choice of anode material determines crystal orientation. The film supports exceptionally efficient migration of both free carriers and excitons: the free carrier mobility reaches over 30 cm2  V-1  s-1 , whereas the excitons are delocalized with a low binding energy of 118.5 meV and a remarkable exciton diffusion length of 45 nm.

Aggregation caused quenching to aggregation induced emission transformation: a precise tuning based on BN-doped polycyclic aromatic hydrocarbons toward subcellular organelle specific imaging

Polycyclic aromatic hydrocarbons (PAHs) with boron–nitrogen (BN) moieties have attracted tremendous interest due to their intriguing electronic and optoelectronic properties. However, most of the BN-fused π-systems reported to date are difficult to modify and exhibit traditional aggregation-caused quenching (ACQ) characteristics. This phenomenon greatly limits their scope of application. Thus, continuing efforts to seek novel, structurally distinct and functionally diverse structures are highly desirable. Herein, we proposed a one-stone-two-birds strategy including simultaneous exploration of reactivity and tuning of the optical and electronic properties for BN-containing π-skeletons through flexible regioselective functionalization engineering. In this way, three novel functionalized BN luminogens (DPA-BN-BFT, MeO-DPA-BN-BFT and DMA-DPA-BN-BFT) with similar structures were obtained. Intriguingly, DPA-BN-BFT, MeO-DPA-BN-BFT and DMA-DPA-BN-BFT exhibit completely different emission behaviors. Fluorogens DPA-BN-BFT and MeO-DPA-BN-BFT exhibit a typical ACQ effect; in sharp contrast, DMA-DPA-BN-BFT possesses a prominent aggregation induced emission (AIE) effect. To the best of our knowledge, this is the first report to integrate ACQ and AIE properties into one BN aromatic backbone with subtle modified structures. Comprehensive analysis of the crystal structure and theoretical calculations reveal that relatively large twisting angles, multiple intermolecular interactions and tight crystal packing modes endow DMA-DPA-BN-BFT with strong AIE behavior. More importantly, cell imaging demonstrated that luminescent materials DPA-BN-BFT and DMA-DPA-BN-BFT can highly selectively and sensitively detect lipid droplets (LDs) in living MCF-7 cells. Overall, this work provides a new viewpoint of the rational design and synthesis of advanced BN–polycyclic aromatics with AIE features and triggers the discovery of new functions and properties of azaborine chemistry.

A one-stone-two-birds strategy including simultaneous exploration of reactivity and tuning of the optical and electronic properties for BN-fused polycyclic aromatics through flexible regioselective functionalization engineering is presented.

Nitrogen-Containing Perylene Diimides: Molecular Design, Robust Aggregated Structures, and Advances in n-Type Organic Semiconductors

ConspectusOrganic semiconductors (OSCs) have attracted much attention because of their potential applications for flexible and printed electronic devices and thus have been extensively investigated in a variety of research fields, such as organic chemistry, solid-state physics, and device physics and engineering. Organic thin-film transistors (OTFTs), a class of OSC-based devices, have been expected to be an alternative of silicon-based metal oxide semiconductor field-effect transistors (MOSFETs), which is the indispensable element for most of the current electronic devices. However, the noncovalently aggregated, van der Waals solid nature of the OSCs, by contrast to covalently bound silicon, conventionally exhibits lower carrier mobilities, limiting the practical applications of OTFTs. In particular, electron-transporting (i.e., n-type) OSCs lag behind their hole-transporting (p-type) counterparts in carrier mobility and ambient stability as OTFTs. This is primarily because of the difficulty in achieving compatibility between the aggregated structure exhibiting excellent carrier mobility and that with enough electron affinity. Recent understandings of carrier transport in OSCs explain that large and two-dimensionally isotropic transfer integrals coupled with small fluctuations are crucial for high carrier mobilities. In addition, from a practical point of view, the compatibility with practical device processes is highly required. Rational molecular design principles, therefore, are still demanded for developing OSCs and OTFTs toward high-end device applications.Herein, we will show our recent progress in the development of n-type OSCs with the key π-electron core (π-core) of benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) on the basis of single-crystal OTFT technologies and the band-transport model enabled by two-dimensional molecular packing arrangements. The critical point is the introduction of electronegative nitrogen atoms into the π-core: the nitrogen atoms in BQQDI not only deepen the molecular orbital energies but also allow hydrogen-bonding-like attractive intermolecular interactions to control the aggregated structures, unlike the conventional role of the nitrogen introduced into OSCs only for the former role. Hence, the BQQDI analogues exhibit air-stable OTFT behavior and two-dimensional brickwork packing structures. Specifically, phenethyl-substituted analogue (PhC₂-BQQDI) has been shown as the first principal BQQDI-based material, demonstrating solution-processable thin-film single crystals, fewer anisotropic transfer integrals, and an effective suppression of molecular motions, leading to band-like electron-transport properties and stress-durable n-channel OTFT performances, in conjunction with the support of computational calculations. Insights into more fundamental points of view have been found by side-chain derivatization and OTFT studies on polycrystalline and single-crystal films. We hope that this Account provides readers with new strategies for designing high-performance OSCs by two-dimensional control of the aggregated structures.

Stereo-electronic effect of perfluoropropyl group on solid state molecular packing of isomeric dibenzo [a,c]phenazine derivatives

We report here the synthesis, characterization, and crystal structures of three perfluoropropylated dibenzo [a,c]phenazine constitutional isomers where the only differences among them are the position of perfluoropropyl substituents. The crystal...

Influence of π-Endcaps on the Performance of Functionalized Quinolines for p-Channel OFETs

This study investigates the influence of aryl and ethynyl linkers as well the effect of various pi-end-groups on the performance of the quinoline-based organic field-effect transistors. A series of new functionalized quinolines with D-π-A-π-D and A-π-A-π-A architectures are designed and synthesized via the Sonagashira cross-coupling reaction. All the new compounds are well characterized and their photophysical properties are studied. The bottom gate-top contact-organic field-effect transistors devices are fabricated using the spin-coating technique. By employing the pre and post-annealing technique, films with uniform surface coverage are obtained. The variation in the end-groups results in versatile packing arrangements which determine their good charge transport properties. The p-channel transistor behavior is observed for all the new compounds. Among the molecules studied, methoxyphenyl and thiophen-2-yl terminal functionalized with D-π-A-π-D architecture exhibit the higher p-channel transistor characteristics with hole mobilities of 1.39 and 1.33 cm² V^-1 s^-1 , respectively. The good charge carrier mobilities are supported by an electron-donating methoxy group and thiophene as the end-groups with high highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) levels, extensive π-conjugation, and better self-assembly.

Near-Infrared Nonfullerene Acceptors Based on 4H-Cyclopenta[1,2-b:5,4-b']dithiophene for Organic Solar Cells and Organic Field-Effect Transistors

The development of nonfullerene small molecular acceptors (NF-SMAs) has dominated the improvement of efficiencies for organic solar cells and the near-infrared (NIR) absorption is the primary feature of NF-SMAs compared with fullerene derivatives. In this article, a series of acceptor-donor-acceptor-structured NF-SMAs (named CPICs) containing 4H-cyclopenta[1,2-b : 5,4-b']dithiophene (CPDT) electron donor and F-substituted 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) as electron acceptor were designed and synthesized. With the increase of CPDT units, the elongated conjugations broadened the absorption range of the acceptors and tuned their energy levels sequentially. Therefore, their charge-transporting polarities switched from electron-only type to bipolar mode in organic field-effect transistors. Moreover, these changes also influenced the voltages, current densities, and eventual PCEs of their corresponding cells. When blending with PBDB-T, a champion efficiency of 10.01% was achieved in CPIC-2 based cells. This work demonstrated the importance of absorptions, suitable energy levels and charge transports in improving the efficiencies of organic solar cells.

Mixed Ionic and Electronic Conduction in Small-Molecule Semiconductors

Small-molecule organic semiconductors have displayed remarkable electronic properties with a multitude of π-conjugated structures developed and fine-tuned over recent years to afford highly efficient hole- and electron-transporting materials. Already making a significant impact on organic electronic applications including organic field-effect transistors and solar cells, this class of materials is also now naturally being considered for the emerging field of organic bioelectronics. In efforts aimed at identifying and developing (semi)conducting materials for bioelectronic applications, particular attention has been placed on materials displaying mixed ionic and electronic conduction to interface efficiently with the inherently ionic biological world. Such mixed conductors are conveniently evaluated using an organic electrochemical transistor, which further presents itself as an ideal bioelectronic device for transducing biological signals into electrical signals. Here, we review recent literature relevant for the design of small-molecule mixed ionic and electronic conductors. We assess important classes of p- and n-type small-molecule semiconductors, consider structural modifications relevant for mixed conduction and for specific interactions with ionic species, and discuss the outlook of small-molecule semiconductors in the context of organic bioelectronics.

Modulation of π-stacking modes and photophysical properties of an organic semiconductor through isosteric cocrystallization

We report on the control of π-stacking modes (herringbone vs slipped-stack) and photophysical properties of 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene (BP4VA), an anthracene-based organic semiconductor (OSC), by isosteric cocrystallization (i.e., the replacement of one functional group in a coformer with another of "similar" electronic structure) with 2,4,6-trihalophenols (3X-ph-OH, where X = Cl, Br, and I). Specifically, BP4VA organizes as slipped-stacks when cocrystallized with 3Cl-ph-OH and 3Br-ph-OH, while cocrystallization with 3I-ph-OH results in a herringbone mode. The photoluminescence and molecular frontier orbital energy levels of BP4VA were effectively modulated by the presence of 3X-ph-OH through cocrystallization. We envisage that the cocrystallization of OSCs with minimal changes in cocrystal formers can provide access to convenient structural and property diversification for advanced single-crystal electronics.

Correlating Charge Transport Properties of Conjugated Polymers in Solution Aggregates and Thin-Film Aggregates

The role of solution aggregates on the charge transport process of conjugated polymers in electronic devices has gained increasing attention; however, the correlation of the charge carrier mobilities between the solution aggregates and the solid-state films remains elusive. Herein, three polymers, FBDOPV-2T, FBDOPV-2F2T, and FBDOPV-4F2T, are designed and synthesized with distinct aggregation behavior in solution. By combining contact-free ultrafast terahertz (THz) spectroscopy and field-effect transistor measurements, we track the charge carrier mobility of the aggregates of these polymers from the solution to the thin-film state. Remarkably, the mobility of these three polymers is found to follow nearly the same trend (FBDOPV-2T>FBDOPV-2F2T≫FBDOPV-4F2T) in both solutions and thin-film states. The quantitative mobility correlation indicates that the charge transport properties of solution aggregates play a critical role in determining the thin-film charge transport properties and final device performance. Our results highlight the importance of investigating and controlling solution aggregation structures towards efficient organic electronic devices.

The Rise of Silicon Phthalocyanine: From Organic Photovoltaics to Organic Thin Film Transistors

Silicon phthalocyanines are emerging n-type semiconductors for use in organic photovoltaics (OPVs) and organic thin-film transistors (OTFTs). Their low synthetic complexity paired with their versatile axial group facilitates the fine-tuning of their chemical properties, solution properties and processing characteristics without significantly affecting their frontier orbital levels or their absorption properties. The crystal engineering and film forming characteristics of silicon phthalocyanine semiconductors can be tuned through appropriate axial group functionalization, therefore facilitating their integration into both OTFTs and OPVs by solution processing or vapor deposition. This Spotlight on Applications will discuss recent advances in the integration of this exciting class of phthalocyanine into OTFTs and OPVs and highlights their promising future.

Supramolecular Alloys from Fluorinated Hybrid Tri4 Di6 Imine Cages

To create innovative materials, efficient control and engineering of pore sizes and their characteristics, crystallinity and stability is required. Eight hybrid Tri4 Di6 imine cages with a tunable degree of fluorination and one fully fluorinated Tri4 Di6 imine cage are investigated. Although the fluorinated and the non-fluorinated building blocks used herein differ vastly in reactivity, it was possible to gain control over the outcome of the self-assembly process, by carefully controlling the feed ratio. This represents the first hybrid material based on fluorinated/hydrogenated porous organic cages (POCs). These cages with unlimited miscibility in the solid state were obtained as highly crystalline samples after recrystallization and even showed retention of the crystal lattice, forming alloys. All mixtures and the fully fluorinated Tri4 Di6 imine cage were analyzed by MALDI-MS, single-crystal XRD, powder XRD and in regard to thermal stability (TGA).

Multi-level aggregation of conjugated small molecules and polymers: from morphology control to physical insights

Aggregation of molecules is a multi-molecular phenomenon occurring when two or more molecules behave differently from discrete molecules due to their intermolecular interactions. Moving beyond single molecules, aggregation usually demonstrates evolutive or wholly emerging new functionalities relative to the molecular components. Conjugated small molecules and polymers interact with each other, resulting in complex solution-state aggregates and solid-state microstructures. Optoelectronic properties of conjugated small molecules and polymers are sensitively determined by their aggregation states across a broad range of spatial scales. This review focused on the aggregation ranging from molecular structure, intermolecular interactions, solution-state assemblies, and solid-state microstructures of conjugated small molecules and polymers. We addressed the importance of such aggregation in filling the gaps from the molecular level to device functions and highlighted the multi-scale structures and properties at different scales. From the view of multi-level aggregation behaviors, we divided the whole process from the molecule to devices into several parts: molecular design, solvation, solution-state aggregation, crystal engineering, and solid-state microstructures. We summarized the progress and challenges of relationships between optoelectronic properties and multi-level aggregation. We believe aggregation science will become an interdisciplinary research field and serves as a general platform to develop future materials with the desired functions.

Examination of aggregation-induced enhanced emission in a propeller-shaped chiral nonconjugated blue emitter from restricted intramolecular rotation and J-type ππ stacking interactions

Herein, to get rid of aggregation-caused quenching (ACQ) in the solid phase, which is generally observed in π-conjugated planar molecules, a new chiral nonconjugated molecule with the propeller-shaped blue emitter property was prepared and characterized, and its photoluminescence behavior in the solid and solution phases were investigated through single crystal X-ray crystallography and photophysical studies. To further understand the aggregation-induced enhanced emission process (AIEE), concentration effect and solvent effect on the fluorescence properties of the solution phase and fluorescence quantum yield measurements in the solid and solution states were performed. In addition, thermal gravimetric analysis (TGA), cyclic voltammogram measurements (CV) and theoretical analysis of the molecule were carried out. According to the results of the experimental work done, the molecule showed aggregation-induced enhanced blue emission (AIEE) in the crystal state, which arose from the strong J-type ππ stacking interactions between the adjacent rings of the molecules, and the restricted intramolecular rotation process (RIR). The solvent polarity-dependent emission also verified the AIEE process. Therefore, combining the advantages of nonconjugation and chirality properties in the synthesis of the molecule afforded a new, unusual AIEE material and provided a new way for the design of a nonconjugated chiral fluorescent optoelectronic material.

Toward Highly Robust Nonvolatile Multilevel Memory by Fine Tuning of the Nanostructural Crystalline Solid-State Order

Organic resistive memory (ORM) offers great promise for next-generation high-density multilevel-cell (MLC) data storage. However, the fine tuning of crystalline order among its active layer still remains challenging, which largely restricts ORM behavior. Here, an exceptional solid-state transition from disordered orientations to highly-uniform orientation within the ORM layer is facilely triggered via molecular strategic tailoring. Two diketopyrrolopyrrole-based small molecular analogues (NI₁ TDPP and NI₂ TDPP) are demonstrated to display different symmetry. The asymmetric NI₁ TDPP shows an irregular solid-state texture, while the centro-symmetric NI₂ TDPP conforms to an ordered out-of-plane single-crystalline pattern that aligns with the foremost charge transportation along the substrate normal, and exhibits excellent MLC memory characteristics. Moreover, this highly oriented pattern guarantees the large-area film uniformity, leading to the twofold increase in the yield of as-fabricated ORM devices. This study reveals that the solid-state crystalline nanostructural order of organic materials can be controlled by reasonable molecular design to actuate high-performance organic electronic circuits.

Synergistic non-bonding interactions based on diketopyrrolo-pyrrole for elevated photoacoustic imaging-guided photothermal therapy

Synergistic non-bonding interactions in fluorine and chalcogen-substituted diketopyrrolopyrrole nanoagents for elevated photoacoustic imaging-guided photothermal therapy.

Bis-isatin based polymers with tunable energy levels for organic field-effect transistor applications

Two bis-isatin based building blocks have been synthesized with the aid of non-covalent intramolecular interactions. Their polymers showed p-type or ambipolar charge transport in OFETs.