On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

Kim-Lee, Hyun-Joon; Hong, Seog Woo; Kim, Dong Kyun; Kim, Jinmyoung; Kim, Hong Suk; Chung, Soonwan; Cho, Eun−Hyoung; Kim, Haesung; Lee, Byung-Kyu

doi:10.1038/s41378-020-00203-4

Cited by 13 publications

(11 citation statements)

References 32 publications

(52 reference statements)

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“…Typically, well-defined patterned TCFs or TCEs with feature sizes on the order of sub-micrometer are required to be of any use in high-resolution displays or narrow-bezel touch sensors . For example, the Samsung Galaxy S10 display has a pixel size of 46 μm (550 ppi) . In addition to high resolution, the MNW patterns should also exhibit high electrical conductivity and/or optical transparency.…”

Section: Key Patterning Parametersmentioning

confidence: 99%

“…38 For example, the Samsung Galaxy S10 display has a pixel size of 46 μm (550 ppi). 39 In addition to high resolution, the MNW patterns should also exhibit high electrical conductivity and/or optical transparency. The patterned MNW line widths using different patterning methods versus sheet resistance/electrical conductivity are shown in Figure 1a,b.…”

Section: Key Patterning Parametersmentioning

confidence: 99%

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Patterning of Metal Nanowire Networks: Methods and Applications

Huang

Zhu

2021

ACS Appl. Mater. Interfaces

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With the advance in flexible and stretchable electronics, one-dimensional nanomaterials such as metal nanowires have drawn much attention in the past 10 years or so. Metal nanowires, especially silver nanowires, have been recognized as promising candidate materials for flexible and stretchable electronics. Owing to their high electrical conductivity and high aspect ratio, metal nanowires can form electrical percolation networks, maintaining high electrical conductivity under deformation (e.g., bending and stretching). Apart from coating metal nanowires for making large-area transparent conductive films, many applications require patterned metal nanowires as electrodes and interconnects. Precise patterning of metal nanowire networks is crucial to achieve high device performances. Therefore, a high-resolution, designable, and scalable patterning of metal nanowire networks is important but remains a critical challenge for fabricating high-performance electronic devices. This review summarizes recent advances in patterning of metal nanowire networks, using subtractive methods, additive methods of nanowire dispersions, and printing methods. Representative device applications of the patterned metal nanowire networks are presented. Finally, challenges and important directions in the area of the patterning of metal nanowire networks for device applications are discussed.

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Section: Key Patterning Parametersmentioning

confidence: 99%

Section: Key Patterning Parametersmentioning

confidence: 99%

Patterning of Metal Nanowire Networks: Methods and Applications

Huang

Zhu

2021

ACS Appl. Mater. Interfaces

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“…The fingerprint function should be integrated into the display to increase screen size and achieve a more pleasant user experience. However, there are certain challenges: The components located in the path where the reflected light by the fingerprint enters the sensor must be transparent or the display image quality may be degraded, including the moiré effect [1]- [3]. Despite the degradation in image quality, the sensor can only recognize the fingerprint where the sensor is located, whereas each person prefers a different location to place a finger.…”

Section: Introductionmentioning

confidence: 99%

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

et al. 2022

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This paper proposes a new architecture for a micro light emitting diode (micro-LED) display featuring fingerprint detection without any additional light emitting and sensing devices in mobile applications. This paper proposes that conventional LEDs can be used as photodetectors in active-matrix pixel circuits. In the area where a finger touched, some LEDs are used as photodetectors and others are used as light emitting sources. The photocurrents of reverse-biased LEDs under various illumination conditions were investigated. The active-matrix circuit was fabricated using a conventional p-type low-temperature polycrystalline silicon (LTPS) process. The fabricated pixel circuit could distinguish the intensity of the incident light to the sensing LED. The voltage across the sensing LED (VLED) was investigated when the pixel density was 400 pixels per inch (ppi) and the cover glass thickness was 30 μm. The experimental results showed that the VLED changed by 0.5 V for 16.7 ms when red, green, or blue LEDs emitted 150 cd/m 2 , 400 cd/m 2 , or 100 cd/m 2 , respectively. 19 LED array with 1.5 mm pitch (p) and 2 mm thick cover glass was fabricated to emulate the LED display with 400 ppi and 30 μm thick cover glass. It is found that an emitting LED affected the sensing LEDs within the distance of 3p by comparing VLEDs. VLEDs were measured when the material on the cover glass was air and water with white pigments (water/W). ΔVLEDs were 0.29 V and 1.13 V for glass-air and glass-water/W cases, respectively. It is found that the lights incident on the sensing LED comprised not only reflected lights by Fresnel reflection at the glass interface but also scattered lights in the water/W. A 75 magnified fake fingerprint was fabricated. Its material was poly-lactic acid with refractive index of 1.465 which is very close to that of a fingertip. Measured ΔVLEDs at ridges and valleys were 0.48 V and 0.22 V, respectively. The ratio of 0.48 / 0.22 was 2.18 that is very close to 1.91 that is the ratio of light intensity at the ridge to that at the valley obtained by the calculation. This verifies that the proposed micro-LED display distinguishes the ridges and valleys of fingerprint without any help from any additional devices.

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“…Transparent conducting electrodes (TCEs) serve an indispensable role in a wide range of optoelectronic devices including photovoltaics (PVs), supercapacitors, smart windows, touch screens, and organic light-emitting diodes . Over the past decade a number of innovative approaches have been reported for the fabrication of TCEs based on a fine grid of opaque metal lines together with a high transparency, low conductivity layer that spans the gaps between them. − This approach to TCE design offers a path for achieving performance matched to the requirements for several potentially very low cost, emerging thin film PVs, including perovskite PVs: A sheet resistance much less than 10 Ohms per square and far-field transparency >80% for light wavelengths in the range 400–900 nm. − Metal mesh electrodes are particularly attractive for organic PVs and perovskite PVs, as a replacement for the transparent conducting oxides (TCOs) indium-tin oxide (ITO) and fluorine-doped tin oxide (FTO) currently used.…”

Section: Introductionmentioning

confidence: 99%

“…Transparent conducting electrodes (TCEs) serve an indispensable role in a wide range of optoelectronic devices including photovoltaics (PVs), 1 supercapacitors, 2 smart windows, 3 touch screens, 4 and organic light-emitting diodes. 5 Over the past decade a number of innovative approaches have been reported for the fabrication of TCEs based on a fine grid of opaque metal lines together with a high transparency, low conductivity layer that spans the gaps between them.…”

Section: ■ Introductionmentioning

confidence: 99%

A Microcontact-Printed Nickel-Passivated Copper Grid Electrode for Perovskite Photovoltaics

Wijesekara

Walker

Han

et al. 2021

ACS Appl. Energy Mater.

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We report a novel transparent copper-based grid electrode fabricated by microcontact printing that offers high stability toward oxidation in air. Passivation is achieved using a 2.5 nm thick layer of nickel buried just below the surface of the copper film from which the grid is etched. This approach to electrode passivation retains the advantages associated with using microcontact printing lithography for grid fabrication of very fast resist deposition and compatibility with the low cost, low toxicity etchant ammonium persulfate. The processes of patterned resist deposition and metal etching is complete within less than 1 min. Using this approach, a grid electrode with a far-field transparency of 82% across the wavelength range 300–900 nm and a sheet resistance of 6.8 Ω sq−1 is demonstrated, which is shown to be a promising alternative to indium-tin oxide as the transparent electrode in perovskite photovoltaic devices.

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On-screen fingerprint sensor with optically and electrically tailored transparent electrode patterns for use on high-resolution mobile displays

Cited by 13 publications

References 32 publications

Patterning of Metal Nanowire Networks: Methods and Applications

Patterning of Metal Nanowire Networks: Methods and Applications

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

A Microcontact-Printed Nickel-Passivated Copper Grid Electrode for Perovskite Photovoltaics

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