Herein, we report the rational design of practical small-molecule organic semiconductors based on a π-electron skeleton of benzothieno [3,2-b]naphtho [2,3-b]thiophene (BTNT) whose layered herringbone (LHB) packing is intentionally modulated by the designated asymmetric substitutions with the phenyl group and normal alkyl chains. The thermal stability of the hybrid BTNT core is high enough, as it lies between those of dinaphtho[2,3-b:2′,3′-f ]thieno[3,2-b]thiophene (DNTT) and benzothieno[3,2-b]benzothiophene (BTBT), although the solvent solubility for the substituted BTNT at ordinary 2,8substituting positions by the alkyl chain and phenyl group remains extremely low. We show in the BTBT and BTNT derivatives that the tuning of the substituting position works to slightly bend the rodlike organic semiconductor molecules and thus to decrease the cohesive energy of the crystals with retention of the bilayer-type herringbone (b-LHB) packing for the asymmetric rodlike molecules. This modification eventually leads to an increase in solvent solubility, a decrease in phase transition temperature, and the suppression of liquid-crystalline phases at high temperatures. By using the substituting effect, we successfully achieve the organic semiconductors with modulated alkylated Ph-BTNT that exhibits both a sufficiently high solvent solubility and a sufficiently high thermal stability. The variation in the crystal packing also enhances the intermolecular transfer integrals along the T-shaped contacts within the intralayer herringbone packing. Spin coating of the material under ambient conditions affords high-performance bottom-gate, bottom-contact organic thin-film transistors, exhibiting high thermal durability in the device characteristics below 150 °C. The obtained devices also exhibit a higher mobility, a lower threshold voltage, and a smaller subthreshold swing, by initial thermal treatment at 140 °C, composed to those of the as-prepared films, because the thermal treatment stabilizes the b-LHB packing and thus suppresses the residual minority holes and shallow traps. These findings should be crucial in the design and development of organic semiconductor materials for practical printed electronics applications.

In this paper, we describe a three-layer-stacked color image sensor comprising two organic photoconductive films (OPFs) with thin-film transistor-based readout circuits and a complementary metal–oxide–semiconductor (CMOS) image sensor. In this three-layer-stacked sensor, a blue-sensitive OPF selectively absorbs blue light, a green-sensitive OPF selectively absorbs green light, and a CMOS image sensor (CIS) receives red light. Color video imaging operation at 60 frames per second was confirmed for a prototype sensor having 320 × 240 pixels with a pixel pitch of 20 μm without a color filter array, and good color separation and a linear response of the sensor were achieved owing to the combination of the CIS and color-selective OPFs.

Blended junctions are indispensable for organic solar cells; however, the fabrication of electron and hole transport routes in blended cells remains quite challenging. Herein, a lateral alternating multilayered junction using a high-mobility organic semiconductor is proposed and demonstrated. A total of 93% of the photogenerated electrons and holes are laterally collected over a long distance (0.14 mm). The exciton-collection efficiency reaches 75% in a lateral alternating multilayered junction with a layer thickness of 10 nm. A lateral organic alternating multilayered junction that completely collects both excitons and carriers can be an alternative blended junction for organic solar cells.

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In this work, a thermal molding technique is proposed for the fabrication of plastic electronics on curved surfaces, enabling the preparation of plastic films with freely designed shapes. The induced strain distribution observed in poly(ethylene naphthalate) films when planar sheets were deformed into hemispherical surfaces clearly indicated that natural thermal contraction played an important role in the formation of the curved surface. A fingertip-shaped organic thin-film transistor array molded from a real human finger was fabricated, and slight deformation induced by touching an object was detected from the drain current response. This type of device will lead to the development of robot fingers equipped with a sensitive tactile sense for precision work such as palpation or surgery.