Hideaki Komiyama

Thermally Activated Delayed Fluorescence Polymers for Efficient Solution-Processed Organic Light-Emitting Diodes.

Thermally activated delayed fluorescence (TADF) π-conjugated polymers are developed for solution-processed TADF-OLEDs. Benzophenone-based alternating donor-acceptor structures contribute to the small ∆EST , enabling efficient exciton-harvesting through TADF. Solution-processed OLEDs using the TADF polymers as emitters can achieve high maximum external electroluminescence efficiencies of up to 9.3%.

Solution-grown unidirectionally oriented crystalline thin films of a U-shaped thienoacene-based semiconductor for high-performance organic field-effect transistors

We propose a new design strategy for high-performance organic semiconductors, wherein we utilize 2,10-dioctyl-bis(benzo[4,5]thieno)[2,3-b:3′,2′-d]thiophene, having an overall U-shaped configuration, for preferable self-organization into bilayer lamellar assemblies. Hole mobilities as high as 3.8 cm2 V−1 s−1 and large anisotropic conduction can be attained in organic field-effect transistors incorporating its dip-coated crystalline thin films.

Star-shaped and linear π-conjugated oligomers consisting of a tetrathienoanthracene core and multiple diketopyrrolopyrrole arms for organic solar cells

Summary Solution-processable star-shaped and linear π-conjugated oligomers consisting of an electron-donating tetrathienoanthracene (TTA) core and electron-accepting diketopyrrolopyrrole (DPP) arms, namely, TTA-DPP4 and TTA-DPP2, were designed and synthesized. Based on density functional theory calculations, the star-shaped TTA-DPP4 has a larger oscillator strength than the linear TTA-DPP2, and consequently, better photoabsorption property over a wide range of visible wavelengths. The photovoltaic properties of organic solar cells based on TTA-DPP4 and TTA-DPP2 with a fullerene derivative were evaluated by varying the thickness of the bulk heterojunction active layer. As a result of the enhanced visible absorption properties of the star-shaped π-conjugated structure, better photovoltaic performances were obtained with relatively thin active layers (40–60 nm).