Min Hee Choi

Bio: Min Hee Choi is an academic researcher from Kyung Hee University. The author has contributed to research in topics: Thin-film transistor & Pentacene. The author has an hindex of 9, co-authored 16 publications receiving 307 citations.

Process optimization of organic thin-film transistor by ink-jet printing of DH4T on plastic

Abstract: The authors studied the organic thin-film transistor (OTFT) with a solution based dihexylquaterthiophene (DH4T) by ink-jet printing. The DH4T with 1.0wt% solution in dichlorobenzene was used for printing of an active layer of OTFTs. In order to obtain a smooth and uniform film of DH4T, the substrate temperature was elevated to 60°C and the printing was performed by an overlapping method. The OTFT on plastic exhibited an on/off current ratio of ∼107, a threshold voltage of −0.25V, a gate voltage swing of 0.45V/decade, and a field-effect mobility of 0.043cm2∕Vs in the saturation region.

Dependence of persistent photocurrent on gate bias in inkjet printed organic thin-film transistor

Abstract: We have studied the photocurrent decay under gate bias in organic thin-film transistor (OTFT) using inkjet printed α,ω-dihexylquarterthiophene layer. The OTFT shows high photocurrents under light illumination and very slow decay of photocurrents under positive gate voltage. This is due to the gate voltage-controlled trapping and detrapping of the electrons near the interface. With increasing exposure time, more electrons are trapped and thus make the photocurrent decay slower. It is found that there is a power-law dependence between light exposure time and decay time constant.

High-Performance Flexible TFT Circuits Using TIPS Pentacene and Polymer Blend on Plastic

Abstract: We report the high-performance circuit on 25-μm polyimide substrate with organic thin-film transistors (TFTs) (OTFTs) using 6,13-bis(triisopropyl-silylethynyl) pentacene and polymer blending. Because of high mobility (0.64 cm2/V·s) and low threshold voltage (<;|1 V|) of the TFTs, an 11-stage ring oscillator (RO) made of these TFTs exhibits the switching speed of 31.4 kHz at the supply voltage of 20 V. The output waveforms of the RO change little after 5000 times bending with a radius of curvature of 2 mm, and thus, the OTFT circuits can be applied to very flexible electronics.

Recent Progress in Inkjet‐Printed Thin‐Film Transistors

Abstract: Drop-on-demand inkjet printing is one of the most attractive techniques from a manufacturing perspective due to the possibility of fabrication from a digital layout at ambient conditions, thus leading to great opportunities for the realization of low-cost and flexible thin-film devices. Over the past decades, a variety of inkjet-printed applications including thin-film transistors (TFTs), radio-frequency identification devices, sensors, and displays have been explored. In particular, many research groups have made great efforts to realize high-performance TFTs, for application as potential driving components of ubiquitous wearable electronics. Although there are still challenges to enable the commercialization of printed TFTs beyond laboratory-scale applications, the field of printed TFTs still attracts significant attention, with remarkable developments in soluble materials and printing methodology. Here, recent progress in printing-based TFTs is presented from materials to applications. Significant efforts to improve the electrical performance and device-yield of printed TFTs to match those of counterparts fabricated using conventional deposition or photolithography methods are highlighted. Moreover, emerging low-dimension printable semiconductors, including carbon nanotubes and transition metal dichalcogenides as well as mature semiconductors, and new-concept printed switching devices, are also discussed.

All-Inkjet-Printed Organic Thin-Film Transistor Inverter on Flexible Plastic Substrate

Abstract: We report an all-inkjet-printed inverter using two p-type organic thin-film transistors (OTFTs) on a flexible plastic substrate. Metal-organic precursor-type silver ink, poly-4-vinylphenol solution, and 6,13-bis (triisopropylsilylethynyl)-pentacene solution were used to print gate and source/drain electrodes, gate-dielectric layer, and active semiconductor layer, respectively. By optimizing fabrication conditions, we obtained OTFTs with a mobility of 0.02 cm2/V·s, an on/off ratio of 104, and a threshold voltage of -1.2 V, and inverters with good switching performance showing a gain of 7.8 at a supply voltage of VDD = -40 V .

Solution-processable singlet fission photovoltaic devices.

Abstract: We demonstrate the successful incorporation of a solution-processable singlet fission material, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), into photovoltaic devices. TIPS-pentacene rapidly converts high-energy singlet excitons into pairs of triplet excitons via singlet fission, potentially doubling the photocurrent from high-energy photons. Low-energy photons are captured by small-bandgap electron-accepting lead chalcogenide nanocrystals. This is the first solution-processable singlet fission system that performs with substantial efficiency with maximum power conversion efficiencies exceeding 4.8%, and external quantum efficiencies of up to 60% in the TIPS-pentacene absorption range. With PbSe nanocrystal of suitable bandgap, its internal quantum efficiency reaches 170 ± 30%.