2016 APCCAS, Jeju, Republic of Korea

October 25 - 28, 2016 (Tue - Fri), Ramada Plaza Jeju Hotel

<Special Session : Display Driver Interface Circuits>

On-Glass Operational Amplifier using Solution-Processed a-IGZO TFTs

Daejung Kim, Keun-Yeong Choi, Hojin Lee

Abstract

In this paper, we presented a novel operational amplifier (op-amp) only with solution-processed n-type amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFTs and common-source amplifier were fabricated on glass substrate through the solution process and confirmed to show stable electrical characteristics suitable for display driving circuits. Based on the experimental results, we designed an op-amp to have an overall gain of 30.5 dB, a cut-off frequency of 1.47 kHz, and a unit gain frequency of 6.65 kHz when supply voltage was ±15 V. Finally, by constituting the comparator, the proposed op-amp is expected to be used in power control and driving systems for display applications.

SID Display Week 2022, San Jose, USA

May 9 - May 13, 2022 (Mon. - Fri.), McEnery Convention Center

2017 SPIE Photonics West, San Francisco, USA

January 28 - February 2, 2017 (Sat - Thu), The Moscone Center

<Oral Session : Session 1: THz Sources and Detectors I>

Polarization dependent resonance manipulation by terahertz meta-molecules 

Hyunseung Jung, Eunah Heo, Jaemok Koo, Chihun In, Hyunyong Choi, Moon Sung Kang, and Hojin Lee

 Abstract

In this study, we propose polarization dependent resonance manipulation by meta-molecules at terahertz frequencies. The proposed meta-molecules are combined with various numbers of H-shaped meta-atoms, which we refer as ‘moleculization’ of meta-atoms. We confirm that the laterally moleculized H-shaped meta-molecules successfully realize the unique properties that can modulate the resonance frequency for the specific polarization of an incident wave, while can keep one identical resonance frequency for their orthogonal polarization direction, simultaneously. Moreover, for the vertically moleculized H-shaped meta-molecules, we also find that the electromagnetically induced transparency (EIT) –like phenomenon can be achieved for the specific polarization direction, with their exceptional field enhancement properties.

2018 SPIE Photonics West, San Francisco, United States

January 29 - February 1, 2018 (Mon - Thur), The Moscone Center

<Oral Session>

Solution-Processed Coplanar a-InGaZnO Thin Film Transistors with Photo-Patterned Ionic-Polymer Gate Dielectric

Dayoon Lee, Yongchan Kim, and Hojin Lee

 Abstract

We propose novel solution-processed coplanar amorphous indium-gallium-zinc-oxide (a-InGaZnO) thin-film transistors (TFTs) with photo-patterned ionic-polymer gate dielectric. We fabricated and measured the electrical characteristics of our coplanar TFTs, and confirmed the high field-effect mobility (~ 4.36 cm-2/V·s), high on-off ratio (~ 107) and good electrical stability. Based on the developed coplanar a-InGaZnO TFTs, we also have designed and fabricated a NMOS inverter with clear signal inversion for flexible electronics and sensor applications. Through this study, we expect that highly flexible and transparent advanced analog circuits and systems can be realized based on the proposed solution processible coplanar TFTs for human-machine interactions.

IMID 2024, Jeju, Korea

August 20 - August 23, 2024 (Tue. - Fri.), ICC Jeju

Enhanced Optoelectrical Properties of Organic Light-Emitting Diodes by ZnO Nanoparticles Reacted with Organic Solvents 

Changhee Lee, Ryungyu Lee, Keun-Yeong Choi, and Hojin Lee 

Abstract

 In this study, we propose a novel post-processing method aimed at enhancing the Luminance of organic light-emitting diodes (OLEDs). This method leverages the reactivity between zinc oxide (ZnO) and organic solvents to improve device performance. Specifically, we aimed to increase the hole-to-electron matching ratio within the light-emitting layer by deliberately reducing the number of oxygen vacancies. These vacancies serve as pathways for carrier movement, and their reduction through the reaction of ZnO particles with organic solvents results in lowered electron injection. Consequently, this modification effectively increases the generation of excitons in the post-processed devices, leading to a significant improvement in luminance.