Seok-Ju Kang

Dramatic inversion of charge polarity in diketopyrrolopyrrole-based organic field-effect transistors via a simple nitrile group substitution.

A record-breaking high electron mobility of 7.0 cm(2) V(-1) s(-1) for n-channel polymer OFETs is reported. By the incorporation of only one nitrile group as an electron-withdrawing function in the vinyl linkage of the DPP-based copolymer, a dramatic inversion of majority charge-carriers from holes to electrons is achieved.

Ultrahigh Mobility in Solution-Processed Solid-State Electrolyte-Gated Transistors

A new concept of a high-capacitance polymeric dielectric based on high-k polymer and ion gel blends is reported. This solid-state electrolyte gate insulator enables remarkable field-effect mobilities exceeding 10 cm2 V-1 s-1 for common polymer and other semiconductor families at VG ≤ 2 V owing to high areal capacitance (>4 µF cm-2 ) from combined polarization of CF interface dipoles and electrical-double-layer formation.

Room‐Temperature Solution‐Synthesized p‐Type Copper(I) Iodide Semiconductors for Transparent Thin‐Film Transistors and Complementary Electronics

Here, room-temperature solution-processed inorganic p-type copper iodide (CuI) thin-film transistors (TFTs) are reported for the first time. The spin-coated 5 nm thick CuI film has average hole mobility (µFE ) of 0.44 cm2 V-1 s-1 and on/off current ratio of 5 × 102 . Furthermore, µFE increases to 1.93 cm2 V-1 s-1 and operating voltage significantly reduces from 60 to 5 V by using a high permittivity ZrO2 dielectric layer replacing traditional SiO2 . Transparent complementary inverters composed of p-type CuI and n-type indium gallium zinc oxide TFTs are demonstrated with clear inverting characteristics and voltage gain over 4. These outcomes provide effective approaches for solution-processed inorganic p-type semiconductor inks and related electronics.

High-Performance Printed Organic Ambipolar Complementary Inverters with Polyazine Containing Diketopyrrolopyrrole

We report ambipolar organic field effect transistors (OFETs) and complementary inverters based on polyazine containing diketopyrrolopyrrole (PBTDAZ). PDBTAZ OFETs showed well-balanced electron and hole mobilities of 0.13 and 0.12 cm2/(V·s) at a low annealing temperature of 100oC using bottom-contact, top-gate geometry with a CYTOPTM gate dielectric layer. The mobilities were improved to 0.56 cm2/(V·s) by thermal annealing (150°C). The ambipolar complementary-inverter-based PDBTAZ OFETs showed ideal Vinv near half of VDD with a high gain of 15∼20 due the well-balanced electron and hole mobilities.

Diels-Alder Crosslinked Block-Copolymer Gate Dielectrics for Low Voltage Operated Top-Gate Organic Field-Effect Transistors

We report a cross-linkable diblock copolymer at a mild temperature by Diels-Alder click-chemistry for a gate dielectric layer in the top-gate, bottom contact organic field-effect transistors (OFETs). The Diels-Alder reaction between poly[(methyl methacrylate)-co-(9-anthracenyl methyl methacrylate)] (P(MMA-AMA)) and 1,1′-(methylenedi-4,1-phenylene)bismaleimide (MPB) enables the preparation of robust cross-linked films at 100 °C annealing for 10 min. Poly(9,9-dioctylfluorene-alt-bithiophene (F8T2) or poly(3-hexylthiophene) (P3HT) OFETs exhibited charge carrier mobilities of 3 ∼ 4 × 10−3 cm2 V−1 s−1 with the 250 nm thick crosslinked (P(MMA-AMA)) films at gate voltages of less than −20 V. Moreover, the ratio of MMA and AMA was controlled to observe the effects of crosslinking density on the properties of the gate dielectric layer. When the portion of a crosslinkable anthracenyl unit in (P(MMA-AMA)) is increased to 50 mol.% in the base polymer, the gate leakage current of OFETs decreases below 10−8 A at Vg = −20 V.