Asymmetrically Functionalized Electron-Deficient π-Conjugated System for Printed Single-Crystalline Organic Electronics.

Large-area single-crystalline thin films of n-type organic semiconductors (OSCs) fabricated via solution-processed techniques are urgently demanded for high-end electronics. However, the lack of molecular designs that concomitantly offer excellent charge-carrier transport, solution-processability, and chemical/thermal robustness for n-type OSCs limits the understanding of fundamental charge-transport properties and impedes the realization of large-area electronics. The benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) π-electron system with phenethyl substituents (PhC2 -BQQDI) demonstrates high electron mobility and robustness but its strong aggregation results in unsatisfactory solubility and solution-processability. In this work, an asymmetric molecular design approach is reported that harnesses the favorable charge transport of PhC2 -BQQDI, while introducing alkyl chains to improve the solubility and solution-processability. An effective synthetic strategy is developed to obtain the target asymmetric BQQDI (PhC2 -BQQDI-Cn ). Interestingly, linear alkyl chains of PhC2 -BQQDI-Cn (n = 5-7) exhibit an unusual molecular mimicry geometry with a gauche conformation and resilience to dynamic disorders. Asymmetric PhC2 -BQQDI-C5 demonstrates excellent electron mobility and centimeter-scale continuous single-crystalline thin films, which are two orders of magnitude larger than that of PhC2 -BQQDI, allowing for the investigation of electron transport anisotropy and applicable electronics.

Selection of Cord Blood Unit by CD34+ Cell and GM-CFU Numbers and Allele-Level HLA Matching in Single Cord Blood Transplantation.

In Japan, only single-unit cord blood transplantations (CBTs) are typically performed, and their number has increased over the last 23 years, with ongoing improvement in results. In most cases, CBTs with multiple HLA mismatches are used, owing to a low HLA barrier, and lower engraftment rate is a problem that must be overcome. Here, as part of an effort to improve guidelines for the selection and processing of CB units for transplantation, we sought to assess the present status of CBT in Japan and to elucidate factors contributing to the favorable outcomes, focusing in particular on selection by cell components of CB unit and HLA allele matching. We conducted a nationwide study analyzing 13,443 patients who underwent first CBT between in Japan between December 1997 and December 2019 using multivariate regression analysis. Both patient- and transplantation-related variables, such as age and Hematopoietic Cell Transplantation Comorbidity Index, as well as selected CB unit characteristics, were included in the analysis. The interaction analysis elucidated that CB unit selection favoring higher counts of CD34+ cells and granulocyte macrophage colony-forming units (GM-CFU)/kg, but not of total nucleated cells, contributed to improved engraftment after transplantation. Moreover, a higher CD34+ cell dose was associated with improved overall survival (OS). Distinctive HLA allele matching was observed. A 0 or 1 HLA allele mismatch between patient and donor had favorable engraftment and carried significantly lower risks of acute GVHD and chronic GVHD but had a significantly higher leukemia relapse rate, compared with a 3-HLA allele mismatch. HLA-DRB1 mismatches were associated with reduced risk of leukemia relapse. Notably, the number of HLA allele mismatches had no incremental effect on engraftment, acute and chronic GVHD, or relapse incidence. As a result, 5-year overall survival did not differ significantly among patients receiving CB units with 0 to 7 HLA allele mismatches. The main points of CB unit selection are as follows. First, selection according to a higher number of CD34+ cells/kg and then of CFU-GM/kg is recommended to obtain favorable engraftment. A unit with .5 × 105 CD34+ cells/kg is minimally acceptable. For units with a CD34+ cell dose of .5 to 1.0 × 105 cells/kg, applying the parameter of ≥20 to 50 × 103 GM-CFU/kg (66.5% of transplanted CB units in this cohort) is associated with a neutrophil engraftment rate of approximately 90%. A unit with ≥1.0 × 105 CD34+ cells/kg can achieve a ≥90% mean neutrophil engraftment rate. Subsequently, HLA allele matching of HLA-A, -B, -C, and -DRB1 at the 2-field level should be searched for units with 0 or 1 HLA allele mismatch in the host-versus-graft direction for favorable engraftment. Units with 2 to 6 HLA allele mismatches are acceptable in patients age ≥15 years and units with 2 to 4 HLA allele mismatches are acceptable in patients age ≤14 years. Units with HLA-DRB1 and/or -B allele mismatch(es) might not be preferable owing to an increased GVHD risk. Our analysis demonstrates that single-unit CBT with the selection of adequate CD34+/kg and GM-CFU/kg and HLA allele matching showed favorable outcomes in both pediatric and adult patients.

Recent Developments of Actuation Mechanisms for Continuum Robots: A Review.

Traditional rigid robots face significant challenges in congested and tight environments, including bulky size, maneuverability, and safety limitations. Thus, soft continuum robots, inspired by the incredible capabilities of biological appendages such as octopus arms, starfish, and worms, have shown promising performance in complex environments due to their compliance, adaptability, and safety. Different actuation techniques are implemented in soft continuum robots to achieve a smoothly bending backbone, including cable-driven actuators, pneumatic actuators, and hydraulic actuation systems. However, designing and developing efficient actuation mechanisms, motion planning approaches, and control algorithms are challenging due to the high degree of redundancy and non-linearity of soft continuum robots. This article profoundly reviews the merits and drawbacks of soft robots' actuation systems concerning their applications to provide the readers with a brief review reference to explore the recent development of soft robots' actuation mechanisms technology. Moreover, the authors have surveyed the recent review studies in controller design of continuum robots as a guidance for future applications.

Adverse events caused by cord blood infusion in Japan during a 5-year period.

BACKGROUND AND OBJECTIVES: In Japan, cord blood is used for more than half of all unrelated stem cell transplantations. The public cord blood banks (CBBs) have been collecting information on cord blood transplantation-related adverse events from physicians on a voluntary basis, without common definitions of the adverse reactions. The aims of this study were to compare two classification systems to improve the reporting system and to clarify the actual risk from cord blood infusion, which can then provide the impetus to take appropriate measures to reduce adverse events. MATERIALS AND METHODS: We classified the reports according to existing criteria; one is the Proposed Standard Definitions for Surveillance of Non-Infectious Adverse Transfusion Reactions by the International Society of Blood Transfusion (ISBT) Working Party on Haemovigilance, and the other is the Common Terminology Criteria for Adverse Events (CTCAE). There were 140 cases with adverse events reported from April 2014 through March 2019. RESULTS: Twelve cases, such as donor-derived leukaemia/myelodysplastic syndromes (MDS) and chromosomal aberrations reported after engraftment, were excluded from this analysis. Of the 128 cases with adverse events at cord blood infusion, the CTCAE and ISBT criteria could not classify 6 cases and 68 cases, respectively. Classifying by the CTCAE, the most common side effect was hypertension in 35 cases, followed by anaphylaxis, allergic reactions, nausea, urticaria, etc. Serious adverse events (grades 4 and 5) were mainly anaphylaxis, with a frequency of 0.23%. CONCLUSION: It is necessary not only to provide information on adverse events but also to standardize the reporting of adverse events to support measures to reduce them.

Adverse effect of donor-specific anti-human leukocyte antigen (HLA) antibodies directed at HLA-DP/-DQ on engraftment in cord blood transplantation.

BACKGROUND AIMS: While donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) in the recipient before transplantation are associated with graft failure in cord-blood transplantation (CBT), effects of DSAs other than against HLA-A, -B or -DRB1 on transplantation outcomes remained poorly understood. METHODS: We retrospectively analyzed 567 single-unit CBT recipients to evaluate impact of DSAs against HLA-DP and -DQ on CBT outcomes. RESULTS: Among 143 recipients (25.2%) who had anti-HLA antibodies, nine harbored DSAs against HLA-DP or -DQ. DSAs against HLA-DP or -DQ were associated with a significantly lower neutrophil engraftment rate (55.6% versus 91.8%, P = 0.032) and with a marginally lower platelet engraftment rate (46.7% versus 75.3%, P = 0.128) at day 100 after transplantation, compared with patients without anti-HLA antibodies. Time to neutrophil and platelet engraftment in patients with DSAs for HLA-DP or -DQ was significantly longer than that in patients without anti-HLA antibodies (median, 25 versus 21 days, P = 0.002 in neutrophil; median 61 versus 46 days, P = 0.014 in platelet). Cumulative incidence of bacterial infection at day 100 was significantly greater (88.9% versus 57.1%, P = 0.024), and re-transplant-free survival was marginally lower (55.6% versus 76.8%, P = 0.132) in patients with DSAs against HLA-DP or -DQ, compared with those without anti-HLA antibodies. These findings suggest that DSAs against HLA-DP or -DQ lead to unfavorable engraftment, which may increase risk of bacterial infection, and reduce survival soon after CBT. CONCLUSIONS: Our results suggest the importance of evaluating DSAs against HLA-DP and -DQ in recipients before selecting CB units.

Conduction band structure of high-mobility organic semiconductors and partially dressed polaron formation.

The energy band structure provides crucial information on charge transport behaviour in organic semiconductors, such as effective mass, transfer integrals and electron-phonon coupling. Despite the discovery of the valence (the highest occupied molecular orbital (HOMO)) band structure in the 1990s, the conduction band (the lowest unoccupied molecular orbital (LUMO)) has not been experimentally observed. Here we employ angle-resolved low-energy inverse photoelectron spectroscopy to reveal the LUMO band structure of pentacene, a prototypical high-mobility organic semiconductor. The derived transfer integrals and bandwidths from the LUMO are substantially smaller than those predicted by density functional theory calculations. To reproduce this bandwidth reduction, we propose an improved (partially dressed) polaron model that accounts for the electron-intramolecular vibrational interaction with frequency-dependent coupling constants based on Debye relaxation. This model quantitatively reproduces not only the transfer integrals, but also the temperature-dependent HOMO and LUMO bandwidths, and the hole and electron mobilities. The present results demonstrate that electron mobility in high-mobility organic semiconductors is indeed limited by polaron formation.

Mixed-Orbital Charge Transport in N-Shaped Benzene- and Pyrazine-Fused Organic Semiconductors.

The hole-carrier transport of organic semiconductors is widely known to occur via intermolecular orbital overlaps of the highest occupied molecular orbitals (HOMO), though the effect of other occupied molecular orbitals on charge transport is rarely investigated. In this work, we first demonstrate evidence of a mixed-orbital charge transport concept in the high-performance N-shaped decyl-dinaphtho[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (C10-DNBDT-NW), where electronic couplings of the second HOMO (SHOMO) and third HOMO (THOMO) also contribute to the charge transport. We then present the molecular design of an N-shaped bis(naphtho[2',3':4,5]thieno)[2,3-b:2',3'-e]pyrazine (BNTP) π-electron system to induce more pronounced mixed-orbital charge transport by incorporating the pyrazine moiety. An effective synthetic strategy for the pyrazine-fused extended π-electron system is developed. With substituent engineering, the favorable two-dimensional herringbone assembly can be obtained with BNTP, and the decylphenyl-substituted BNTP (C10Ph-BNTP) demonstrates large electronic couplings involving the HOMO, SHOMO, and THOMO in the herringbone assembly. C10Ph-BNTP further shows enhanced mixed-orbital charge transport when the electronic couplings of all three occupied molecular orbitals are taken into consideration, which results in a high hole mobility up to 9.6 cm2 V-1 s-1 in single-crystal thin-film organic field-effect transistors. The present study provides insights into the contribution of HOMO, SHOMO, and THOMO to the mixed-orbital charge transport of organic semiconductors.

Photoemission Tomography of a One-Dimensional Row Structure of a Flat-Lying Picene Multilayer on Ag(110).

We applied photoemission tomography (PT) to a unique one-dimensional row structure of a picene multilayer realized on an anisotropic Ag(110) surface. Taking advantage of the simplified structure of the multilayer film, we successfully deconvoluted the photoelectron momentum maps of three frontier orbitals of picene. Thereafter, the clearly deconvoluted experimental momentum maps were compared to the Fourier transform simulation of the molecular orbitals of picene in detail, enabling not only the evaluation of the electronic structure of the picene in the multilayer but also the determination of the molecular orientation in the multilayer within a few degrees. In addition, the PT results indicated the orientation of the molecules in all layers to be flat-lying. The successful demonstration of PT of the multilayer molecular film marks an important step toward the wide-range utilization of the PT technique.

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.

Optical study of electron and acoustic phonon confinement in ultrathin-body germanium-on-insulator nanolayers.

Nanoelectronics require semiconductor nanomaterials with high electron mobility like Ge nanolayers. Phonon and electron states in nanolayers undergo size-dependent changes induced by confinement and surface effects. Confined electrons and acoustic phonons determine layer optical, electric and thermal properties. Despite scientific and practical significance, their experimental studies in individual nanolayers are still lacking. Thanks to recent progress in the fabrication of high-quality nanolayers, here, we report the thickness dependencies of Raman spectra of acoustic phonons and optical spectra of electrons confined in germanium-on-insulator (GeOI) nanolayers with thicknesses TGeOI = 1-20 nm. We show that for TGeOI > 5 nm, both GeOI acoustic phonon Raman spectra and the E1 electron energy gap display dependencies on TGeOI which are reasonably described by the corresponding phonon and electron confinement theories. Accordingly, TGeOI can be probed using acoustic phonon Raman spectra at TGeOI > 5 nm. However, both confinement theories fail to describe GeOI thickness dependencies at TGeOI < 5 nm. We attribute this discrepancy to an increased influence of the Ge-GeO2 interface disorder with TGeOI reduction. The acoustic phonon data suggest a decrease of Ge normal-to-the-layer longitudinal sound velocity. Generation of interface-disorder-induced dispersionless phonons might contribute to this. The change in GeOI phonon properties at TGeOI < 5 nm might influence E1(TGeOI) dependence via a change in the GeOI electron-phonon interaction. We demonstrate that the Al2O3 coating improves the agreement between experimental and confinement theories, probably, via reduction of disorder at the Ge-GeOx-Al2O3-interface. Our results are important for control of nanolayer-confined electrons and phonons with benefits for modern and future nanoelectronic devices.

Role of Perfluorophenyl Group in the Side Chain of Small-Molecule n-Type Organic Semiconductors in Stress Stability of Single-Crystal Transistors.

Operational stability, such as long-term ambient durability and bias stress stability, is one of the most significant parameters in organic thin-film transistors (OTFTs). The understanding of such stabilities has been mainly devoted to energy levels of frontier orbitals, thin-film morphologies, and device configuration involving gate dielectrics and electrodes, whereas the roles of molecular and aggregated structural features in device stability are seldom discussed. In this Letter, we report a remarkable enhancement of operational stability, especially bias stress, of n-channel single-crystal OTFTs derived from a replacement of phenyl with perfluorophenyl groups in the side chain. Because of the several-molecule-thick single-crystal nature employed for the OTFTs, the crystal-surface properties are thought to be critical, where the surface structure composed of perfluorophenyl moieties could suppress interactions between environmental species and field-induced carriers owing to increased hydrophobicity and steric protection of π-conjugated units.

Approaching isotropic charge transport of n-type organic semiconductors with bulky substituents.

Benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) is an n-type organic semiconductor that has shown unique multi-fold intermolecular hydrogen-bonding interactions, leading to aggregated structures with excellent charge transports and electron mobility properties. However, the strong intermolecular anchoring of BQQDI presents challenges for fine-tuning the molecular assembly and improving the semiconducting properties. Herein, we report the design and synthesis of two BQQDI derivatives with phenyl- and cyclohexyl substituents (Ph-BQQDI and Cy6-BQQDI), where the two organic semiconductors show distinct molecular assemblies and degrees of intermolecular orbital overlaps. In addition, the difference in their packing motifs leads to strikingly different band structures that give rise to contrasting charge-transport capabilities. More specifically, Cy6-BQQDI bearing bulky substituents exhibits isotropic intermolecular orbital overlaps resulting in equal averaged transfer integrals in both π-π stacking directions, even when dynamic disorders are taken into account; whereas Ph-BQQDI exhibits anisotropic averaged transfer integrals in these directions. As a result, Cy6-BQQDI shows excellent device performances in both single-crystalline and polycrystalline thin-film organic field-effect transistors up to 2.3 and 1.0 cm2 V-1 s-1, respectively.

The linkage between medical student readiness for interprofessional learning and interest in community medicine.

OBJECTIVES: The purpose of this study is to investigate the relationship between medical student readiness for interprofessional learning and interest in community medicine prior to incorporating community-oriented interprofessional education into the curriculum. METHODS: A questionnaire was administered to students at Nagasaki University School of Medicine in Japan during each of three consecutive years (N=2244). The Readiness for Interprofessional Learning Scale (RIPLS) was administered in addition to a questionnaire to evaluate interest in community medicine. The Kruskal-Wallis and Steel-Dwass tests were used to determine differences between school years. Correlation between the RIPLS score and interest in community medicine was evaluated with Spearman's rank correlation coefficient. Relationships between RIPLS score and demographic parameters, and interest in community medicine were evaluated with multiple linear regression analysis. RESULTS: Eighty-four percent (1891/2244) of students responded. The RIPLS score was highest in school year 1, followed by year 6, year 5, year 3, and years 4 and 2. Interest in community medicine correlated with the RIPLS score (rs = 0.332, p < 0.001), but less in year 1 (rs = 0.125, p = 0.002) than in other years. RIPLS score was significantly associated with gender, age, school year, interest in community medicine, but not the year that the survey was conducted. CONCLUSIONS: Community-oriented interprofessional education has the potential to improve attitudes towards interprofessional learning. When introducing this promising education into the curriculum from year 1, attracting students' interest in community medicine should be considered.

Coherent Electron Transport in Air-Stable, Printed Single-Crystal Organic Semiconductor and Application to Megahertz Transistors.

Organic semiconductors (OSCs) have attracted growing attention for optoelectronic applications such as field-effect transistors (FETs), and coherent (or band-like) carrier transport properties in OSC single crystals (SCs) have been of interest as they can lead to high carrier mobilities. Recently, such p-type OSC SCs compatible with a printing technology have been used to achieve high-speed FETs; therefore, developments of n-type counterparts may be promising for realizing high-speed complementary organic circuits. Herein, coherent electron transport properties in a printed SC of a state-of-the-art, air-stable n-type OSC, PhC2 -BQQDI, by means of variable-temperature gated Hall effect measurements and X-ray single-crystal diffraction analyses in conjunction with band structure calculations, are reported. Furthermore, the SC FET is tested for high-speed operations, which obtains a cutoff frequency of 4.3 MHz at an operation voltage of 20 V in air. Thus, PhC2 -BQQDI is shown as a new candidate for practical applications of SC-based, organic complementary devices.

Alkyl-Substituted Selenium-Bridged V-Shaped Organic Semiconductors Exhibiting High Hole Mobility and Unusual Aggregation Behavior.

Toward the development of high-performance organic semiconductors (OSCs), carrier mobility is the most important requirement for next-generation OSC-based electronics. The strategy is that OSCs consisting of a highly extended π-electron core exhibit two-dimensional (2D) aggregated structures to offer effective charge transport. However, such OSCs, in general, show poor solubility in common organic solvents, resulting in limited solution processability. This is a critical trade-off between the development of OSCs with simultaneous high carrier mobility and suitable solubility. To address this issue, herein, five-membered ring-fused selenium-bridged V-shaped binaphthalene with decyl substituents (C10-DNS-VW) is developed and synthesized by an efficient method. C10-DNS-VW exhibits significantly high solubility for solution processes. Notably, C10-DNS-VW forms a one-dimensional π-stacked packing motif (1D motif) and a 2D herringbone (HB) packing motif (2D motif), depending on the crystal growth condition. On the other hand, the fabrication of thin films by means of both solution process and vacuum deposition techniques forms only the 2D HB motif. External stress tests such as heating and exposure to solvent vapor indicated that 1D and 2D motifs could be synergistically induced by the total balance of intermolecular interactions. Finally, the single-crystalline films of C10-DNS-VW by solution process exhibit carrier mobility up to 11 cm2 V-1 s-1 with suitable transistor stability under ambient conditions for more than two months, indicating that C10-DNS-VW is one of the most promising candidates for breaking the trade-off in the field of solution-processed technologies.

Frequency of allotype "b" in human platelet antigen 1 to 29 systems among blood donors in Japan estimated using high-resolution melt analysis.

BACKGROUND: Antibodies against human platelet antigens (HPAs) cause thrombocytopenias. It is thus important to know the frequency of "b" allotypes in each HPA system for the diagnosis and treatment of anti-HPA antibody-mediated thrombocytopenia. STUDY DESIGN AND METHODS: Genomic DNA was extracted from peripheral blood cells obtained from 2170 blood donors in Japan and was subjected to high-resolution melt (HRM) analysis using polymerase chain reaction for each of the HPA genes, using 23 primer pairs. For genotyping, the resulting amplicons were classified based on their HRM curves. In some cases, direct sequence analysis was performed after HRM analysis to determine nucleotide substitutions. In cases where amino acid substitutions were predicted, protein expression levels were examined in a cell line using 293T cells. RESULTS: The frequencies of each of the HPA-b genotypes were as follows: HPA-1b, 0.4%; HPA-2b, 11.8%; HPA-3b, 41.3%; HPA-4b, 0.8%; HPA-5b, 4.3%; HPA-6b, 1.9%; HPA-15b, 48.8%; HPA-21b, 0.6%; and "b" allotype in the other HPA systems, 0.0%. Twenty-eight variants were found; nine of them were predicted to cause amino acid substitution. However, expression analysis revealed that they did not affect protein expression levels on the cell surface. CONCLUSION: Nine HPA systems are of primary importance in Japan in potentially triggering thrombocytopenia via the HPA antibodies. Similar studies in other countries or races, together with ours, could provide basic information for clinicians in multiethnic societies.

Robust, high-performance n-type organic semiconductors.

Organic semiconductors (OSCs) are important active materials for the fabrication of next-generation organic-based electronics. However, the development of n-type OSCs lags behind that of p-type OSCs in terms of charge-carrier mobility and environmental stability. This is due to the absence of molecular designs that satisfy the requirements. The present study describes the design and synthesis of n-type OSCs based on challenging molecular features involving a π-electron core containing electronegative N atoms and substituents. The unique π-electron system simultaneously reinforces both electronic and structural interactions. The current n-type OSCs exhibit high electron mobilities with high reliability, atmospheric stability, and robustness against environmental and heat stresses and are superior to other existing n-type OSCs. This molecular design represents a rational strategy for the development of high-end organic-based electronics.

Bent-Shaped p-Type Small-Molecule Organic Semiconductors: A Molecular Design Strategy for Next-Generation Practical Applications.

Significant progress has been made in both molecular design and fundamental scientific understanding of organic semiconductors (OSCs) in recent years. Suitable charge-carrier mobilities (µ) have been obtained by many high-performance OSCs (µ > 10 cm2 V-1 s-1), but drawbacks remain, including low solution processability and poor thermal durability. In addition, since aggregation of OSCs involves weak intermolecular interactions, the molecules are perpetually in thermal motion, even in the solid state, which disrupts charge-carrier transport. These issues limit potential applications of OSCs. The present work examines a molecular design for hole-transporting (p-type) OSCs based on the "bent-shaped" geometry with specific molecular orbital configurations, which aims to enhance effective intermolecular orbital overlaps, stabilize crystal phases, suppress detrimental molecular motions in the solid state, and improve solution processability. The results indicated that such OSCs have high µ and suitable solution processability, and are resistant to ambient and thermal conditions, making them suitable for practical applications.

Charge mobility calculation of organic semiconductors without use of experimental single-crystal data.

Prediction of material properties of newly designed molecules is a long-term goal in organic electronics. In general, it is a difficult problem, because the material properties are dominated by the unknown packing structure. We present a practical method to obtain charge transport properties of organic single crystals, without use of experimental single-crystal data. As a demonstration, we employ the promising molecule C10-DNBDT. We succeeded in quantitative evaluation of charge mobility of the single crystal using our quantum wave-packet dynamical simulation method. Here, the single-crystal data is computationally obtained by searching possible packing structures from structural formula of the molecule. We increase accuracy in identifying the actual crystal structure from suggested ones by using not only crystal energy but also similarity between calculated and experimental powder X-ray diffraction patterns. The proposed methodology can be a theoretical design technique for efficiently developing new high-performance organic semiconductors, since it can estimate the charge transport properties at early stage in the process of material development.

Fabrication of Highly Oriented Multilayer Films of Picene and DNTT on Their Bulklike Monolayer.

Highly oriented, multilayer molecular films of picene and dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) molecules with the long axis parallel to the substrate (parallel configuration, hereafter) were fabricated on their characteristic bulklike monolayer. These molecules form a dense monolayer with a bulklike molecular arrangement on metal surfaces such as Au(111), which allows further stacking of parallel molecules. Indeed, upon adsorption of picene and DNTT on these dense monolayers, growth of straight islands of multilayer without the dendritic layer was observed. Particularly, in the case of picene, one-dimensional islands with lengths over 100 µm were formed and aligned in 3-fold symmetric directions of the substrate, which was not observed in the case of DNTT. X-ray diffraction measurements revealed the presence of [201̅] and [211̅] planes and the absence of the [001] diffractions, indicating that the one-dimensional islands of picene indeed consist of parallel molecules. The formation of huge crystalline islands in the case of picene, in contrast to the case of DNTT, is likely induced by the stronger intermolecular force, as suggested from the calculation of the vibrational energy.