AMSM 2024, Incheon, Korea

October 27 - October 30, 2024 (Sun. - Wen.), Songdo ConvensiA

Monolithic VOC Sensor Circuit Based on a-IGZO TFT

Kyungmin Choi, Keun-Yeong Choi, and Hojin Lee

Abstract

Volatile organic compounds (VOCs) generated in industrial production lines are harmful to human health, prompting significant research into detecting VOC gases. For detection of various VOCs, Amorphous oxide semiconductors (AOS) have been highly researched to achieve high-sensitivity chemo-resistive-type VOCs gas sensors. Especially, amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) are attracting high attention due to their high field-effect mobility, low leakage current, good uniformity, and superior electrical stability at low processing temperatures. In this paper, we propose a monolithic sensor circuit designed to amplify the sensing signal of solution-processed a-IGZO sensor TFTs, achieving high sensitivity. The fabricated a-IGZO sensor TFT showed significant changes in transfer characteristics upon exposure to acetone gas, with decreased resistance and a negative threshold voltage shift. The proposed circuit, comprising three a-IGZO TFTs and one capacitor, demonstrated successful gas sensing through simulation, confirming accurate operation. Through this study, we confirmed that the proposed a-IGZO TFT sensor circuit was successfully operated with accurate gas sensing operations. It is expected that the proposed monolithic sensor circuit can be applied to future VOCs systems with highly sensitive detection.

AMSM 2024, Incheon, Korea

October 27 - October 30, 2024 (Sun. - Wen.), Songdo ConvensiA

Abstract

Organic photodiodes are ideal for advanced flexible electronic applications such as imaging and video photography due to their tunable photophysical properties, low-cost and simple processing methods, and continuously improving performance. In particular, the simple design and thin thickness of organic material-based devices enable the control of optical and geometrical crosstalk, garnering attention for application in image sensors. Utilizing these organic photodiodes in image sensors necessitates their integration into high-density arrays. This approach is essential for achieving the precise and effective performance required for advanced imaging applications. However, the absence of precise pixelation techniques capable of implementing organic light-emitting semiconductor with high production and reliability has limited the realization of high-density organic photodiodes. In this paper, we present a silicone engineered anisotropic lithography of the organic light-emitting semiconductor (OLES) that in-situ forms a non-volatile etch blocking layer during reactive ion etching. This unique feature not only slows the etch rate but also enhances the anisotropy of etch direction, leading to gain delicate control in forming ultrahigh-density multicolor OLES patterns (minimum line width of 2µm) through photolithography. This patterning strategy inspired by silicon etching chemistry is expected to provide new insights into high-density organic photodiodes. Furthermore, the proposed system is expected to be applicable to flexible substrates, extending its use to soft sensor applications such as artificial eyes.

AMSM 2024, Incheon, Korea

October 27 - October 30, 2024 (Sun. - Wen.), Songdo ConvensiA

IMID 2024, Jeju, Korea

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

Terahertz Chiral Metasurface Based on Kirigami Structure for Controlling Circular Dichroism

Kyungbin Cho, Wonwoo Lee, and Hojin Lee

Abstract

 The utilization of terahertz (THz) frequency range in spectroscopy provides immense promise for various applications such as enantiomer identification, biomolecular analysis, medical diagnostics, pharmaceutical assessment, and security screening due to its unique characteristics, including linear wave propagation, object penetration, and low photon energy. Notably, terahertz circular dichroism (TCD) spectroscopy emerges as a potent tool for analyzing material properties and discerning enantiomers in biomolecules like nucleic acids and proteins. However, the inherent low response of biomolecules to circular dichroism (CD) in the THz range presents a formidable obstacle in biomolecular analysis. To address this challenge, chiral metamaterials offer a solution by enabling precise control over electromagnetic wave characteristics such as transmission, phase, and polarization in the THz range, thereby enhancing the amplification of chirality properties in materials. In this study, we propose a novel approach to manipulate TCD utilizing a chiral metasurface based on a kirigami structure.

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.