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SPIE Photonics West 2020, San Francisco, USA

February 1 - 6, 2020 (Sun. - Thur.), Moscone Centor


Active Capacitive Sensor Circuit Using Photo-Patternable Ionic Polymer Gate Dielectric Based Solution-Processed Coplanar a-InGaZnO TFTs

Changhyeon Cho, Yongchan Kim, So Young Kim, Do Hwan Kim, and Hojin Lee



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Abstract


  In this paper, we propose solution-processed coplanar a-InGaZnO TFTs using photo-patternable ionic polyurethane acrylate (i-PUA) polymer as a gate dielectric. In our fabrication process, i-PUA is able to pattern micro-size (30μm) by using photocrosslinking property and maintain high capacitance through EDL. Based on developed TFTs, we fabricated an active pixel sensor (APS) circuit consisting of three coplanar a-InGaZnO TFTs for detecting capacitance changes through the difference of output voltages. Furthermore, we simultaneously fabricated a capacitive pressure sensor using an i-PUA on the same plane so as to integrated APS circuit and capacitive pressure sensor simply. Based on the experimental results, we confirmed that the proposed APS circuit could detect changes in the capacitance through various input pressure-levels in i-PUA based sensor. With these results, we believe that our proposed sensor system using the integration of APS circuit and sensor will be applicable to future wearable, human-interaction display with low-power consumption.

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SPIE Photonics West 2020, San Francisco, USA

February 1 - 6, 2020 (Sun. - Thur.), Moscone Centor


Tandem structured 3-color micro-polymer light-emitting diodes (μ-PLEDs)

Keun-Yeong Choi, Han Wool Park, Do Hwan kim, and Hojin Lee




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Abstract


  In this study, we proposed a tandem structured 3-color micro-patterned polymer light-emitting diodes (μ-PLEDs) for super high-resolution organic light-emitting diode (OLED) micro displays. The proposed 3-color polymer light-emitting diodes consisted of red, green, and blue colored polymers patterned down to 20 μm. For the tandem structure, we adopted the recently developed sol-gel process to obtain the orthogonality of organic semiconductor against the solvents and chemicals so that we could apply the standard photolithography and dry-etch process to achieve micron-size patterns of light-emitting polymers. Experimental results showed that we could achieve the 3 distinct color emissions from our tandem PLEDs fabricated by the standard process, the which was confirmed by EL spectrum and CIE chromaticity diagram.

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SPIE Photonics West 2020, San Francisco, USA

February 1 - 6, 2020 (Sun. - Thur.), Moscone Centor


Polarization Independent Flat Metasurface Lens for Millimeter-Wave Beam Focusing

Wonwoo Lee, Semin Jo, Kanghyeok Lee, Hong Soo Park, Junhyuk Yang, Changkun Park, Sun K. Hong and Hojin Lee


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Abstract


  In this paper, we propose a new polarization independent ultra-thin (<λ/10) single-layer metasurface lens to focus incident electromagnetic waves at millimeter-wave frequency. The proposed metasurface focusing lens consists of the 13 x 13 array supercells with different shapes and sizes representing differential gradient phase at 33GHz range. In addition, each supercell could cover enough phase range to make a focal point at desired distance by arranging the discrete phase distribution for each supercell of the metasurface and controlling the phase of the scattering electromagnetic waves. To confirm the focusing characteristics, the power density distribution of scattering field at the focal plane was analyzed, and the maximum power density was formed at the focal length of 50mm which is half-wavelength distance both on x-z plane and y-z plane for incident plane wave. Base on the experimental results, we could confirm that the wavefront and electromagnetic wave could be successfully manipulated and focused. We expect that the proposed ultrathin and high-efficiency metasurface lens can be widely used in various millimeter-wave applications.

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SPIE Photonics West 2020, San Francisco, USA

February 1 - 6, 2020 (Sun. - Thur.), Moscone Centor


Wireless-Powered VOC Sensor based on Wi-Fi Energy-Harvesting Metamaterial with i-TPU

Heejoo Park, Wonwoo Lee, Hyunseung Jung, So Young Kim, Do Hwan Kim, and Hojin Lee



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Abstract


  In this paper, we propose a wireless-powered VOC sensor system based on energy-harvesting metamaterial combined with ionic thermoplastic polyurethane (i-TPU) channel. The sensor consists of the SRR, rectifier circuit to harvest the RF energy by converting electromagnetic energy into DC voltage, and i-TPU channel to detect VOC with the variation of resistance. For the practical wireless sensing system, we utilized widespread and easily accessible commercial 2.4 GHz Wi-Fi source as external electromagnetic wave energy, and the energy-harvesting metamaterial was designed and optimized to resonate at 2.4 GHz. When i-TPU was exposed to acetone gas as target gas, the diffusivity of ionic liquid (IL) increases leading to decrease in resistance of i-TPU that can be identified with the differential harvested energy induced from variation for resonance property. As a result, according to variation of energy-harvesting rate, the proposed sensor could provide the highly sensitive and ultra-stable wireless VOC sensor system without bulky and complicated measurement system offering great accessibility and simplicity for the sensor systems. In addition, it is expected that the proposed system can be applied to not only for VOC sensors but also for dynamic environmental sensing systems.

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SID Display Week 2023, San Jose, USA

May 12 - May 17, 2024 (Sun. - Fri.), San Jose Convention Center


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Silicone-integrated Photolithography of Small-molecule Phosphorescent Emitter for Ultrahigh-resolution Micro-OLEDs

Ryungyu Lee, Keun-Yeong Choi, Hyukmin Kweon, Borina Ha, Changhee Lee, Soyeon Lee, Seonkwon Kim, Seunghan Lee, Hyobin Ham, Hayoung Lim, Moon-Ki Jeong, Gyurim Park, Joon Hak Oh, Moon Sung Kang, Youngmin You, Jeong Ho Cho, BongSoo Kim, Do Hwan Kim, and Hojin Lee


Abstract


   In this paper, we propose an ultrahigh-resolution organic lightemitting diodes (OLEDs) pixels patterned by conventional photolithography through by incorporating silicone into phosphorescent small-molecule networks. This siliconeintegrated phosphorescent organic light-emitting diode (SIphOLED), in which silicone molecules are homogeneously crosslinked with small-molecule light-emitting materials, can effortlessly achieve to 3,000 PPI ultrahigh-resolution patterns using the photolithography process.

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