Effect of Hydrogen Bonding on Thermally Activated Delayed Fluorescence Behaviors Based on a Study of Hydrate Crystals

Reverse intersystem crossing (RISC) in purely organic molecules has become an attractive research topic since the demonstration of high efficiencies in organic light-emitting diodes using thermally activated delayed fluorescence (TADF). Although the intermolecular interactions have a significant impact on the exciton dynamics, it is generally difficult to identify the quantitative relationship associated with a specific factor. In this work, we used a clathrate crystal with TADF and H2O molecules to evaluate the effect of hydrogen bonding while maintaining molecular conformations and other intermolecular interactions. The hydrogen bonding shifted the charge transfer excited states to lower energies, resulting in superior TADF properties. Although the increase in the RISC rate is considered to enhance the stabilities of TADF molecules, photostability analysis revealed nearly the same degradation speed despite the 3 times faster RISC rate

Green Synthesis of Polycyclic Benzimidazole Derivatives and Organic Semiconductors

Polycyclic benzimidazole derivatives, an important class of compounds in organic electronics and photovoltaics, were prepared using a solvent-free “green” process based on heating carboxylic acid anhydrides and arylene diamines in the presence of zinc acetate in the solid state. Products were isolated and purified directly by train sublimation of the crude reaction mixtures. The reaction conditions were optimized using various carboxylic acid anhydrides. Optical and electrochemical properties of these materials are also described

Green Synthesis of Polycyclic Benzimidazole Derivatives and Organic Semiconductors

Polycyclic benzimidazole derivatives, an important class of compounds in organic electronics and photovoltaics, were prepared using a solvent-free “green” process based on heating carboxylic acid anhydrides and arylene diamines in the presence of zinc acetate in the solid state. Products were isolated and purified directly by train sublimation of the crude reaction mixtures. The reaction conditions were optimized using various carboxylic acid anhydrides. Optical and electrochemical properties of these materials are also described

Field-Effect Transistors Based on Tetraphenyldipyranylidenes and the Sulfur Analogues

Field-Effect Transistors Based on Tetraphenyldipyranylidenes and the Sulfur Analogue

Characterization of New Rubrene Analogues with Heteroaryl Substituents

New rubrene analogues, which are heteroaryl-tetrasubstituted tetracenes, have been developed using a simplified synthesis approach. Their stabilities in solution were improved compared to those of rubrene. The correlation among the molecular structures, crystal structures, and charge transport properties has been investigated and compared with rubrene and various rubrene analogues. Although twisted structures of a tetracene backbone have often been found in single crystal analyses, the planarity might be related to intermolecular interactions rather than the electron donating/withdrawing properties of the heteroaryl side groups. The packing motifs in thiophene-substituted derivatives did not include π-stacking of tetracene cores, which differ from the well-known structure of rubrene. However, furan-substituted derivatives can be crystallized in the π-stacking manner. These differences in the packing structure affect hole transport properties

Synthesis of Semiconducting Polymers through Soluble Precursor Polymers with Thermally Removable Groups and Their Application to Organic Transistors

Novel semiconducting polymers consisting of thiophene and anthracene units without alkyl groups were successfully synthesized through soluble precursor polymers and applied to the organic thin-film transistors (OTFTs). Thermal elimination of leaving groups from the precursor polymers by retro Diels–Alder reaction was proved by thermogravimetric analysis (TGA), FT-IR, and UV–vis spectroscopy. The resulting films of the semiconducting polymers showed good surface morphologies even after thermal elimination, resulting in good semiconducting behavior with mobility of 0.015 cm2 V–1 s–1 in the typical top-contact OTFT. In addition, the devices based on these polymers are stable under ambient conditions and maintained good transistor performance even after being stored in air for 2 months

Synthesis, Physical Properties, and Field-Effect Mobility of Isomerically Pure <i>syn</i>-/<i>anti</i>-Anthradithiophene Derivatives

Isomerically pure <i>syn</i>-/<i>anti</i>-isomers of 2,8-dimethylanthradithiophene (DMADT) were synthesized in five steps and characterized using thermogravimetry, X-ray single crystal analysis, UV–vis absorption, and electrochemical measurements. The physical properties in solution were slightly different for each isomer, whereby the more obvious differences were observed in the solid state. A field-effect transistor using the <i>anti</i>-isomer showed a much higher performance than that using the <i>syn</i>-isomer

Synthesis, Physical Properties, and Field-Effect Mobility of Isomerically Pure <i>syn</i>-/<i>anti</i>-Anthradithiophene Derivatives

Isomerically pure <i>syn</i>-/<i>anti</i>-isomers of 2,8-dimethylanthradithiophene (DMADT) were synthesized in five steps and characterized using thermogravimetry, X-ray single crystal analysis, UV–vis absorption, and electrochemical measurements. The physical properties in solution were slightly different for each isomer, whereby the more obvious differences were observed in the solid state. A field-effect transistor using the <i>anti</i>-isomer showed a much higher performance than that using the <i>syn</i>-isomer

Field-Effect Transistors Based on Tetraphenyldipyranylidenes and the Sulfur Analogues

Field-Effect Transistors Based on Tetraphenyldipyranylidenes and the Sulfur Analogue

Novel Semiconducting Quinone for Air-Stable n-Type Organic Field-Effect Transistors

Quinones are promising moieties for n-type organic semiconductors due to their high electron affinity. Benzo[1,2-b:4,5-b′]dithiophene-4,8-dione derivative with a quinone moiety have been synthesized, characterized, and used as active layer of organic field-effect transistors (OFETs). This derivative has deep LUMO level, leading to efficient charge-carrier injection and air stability. In addition, it forms a columnar structure with efficient intermolecular π−π and horizontal direction interactions, leading to high electron mobilities. In fact, OFET devices fabricated here showed good n-type characteristics, where the electron mobility was 0.15 cm2 V−1 s−1 under vacuum conditions and above 0.1 cm2 V−1 s−1 in air