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nano tech 2023 (February 1-3, 2023)


nanotech 2023 Perovskite QD is useful for wavelength conversion film and CF of LCD

February 1-3, 2023, nano tech 2023 was held in Tokyo Big Sight. Main topics are picked up.


As concerns electronics device, Ise Chemicals and Yamagata University announced to jointly develop a new quantum dot (QD) device using perovskite crystal. It's named as Perovskite Quantum Dots (PeQDs).

PeQDs is a just new QD. In short, emission property is obtained by Nano size function of Nano size perovskite crystal. As you know, perovskite crystal is composed of ABX3 structure. In this material, organic cation such as MA+, transition element ion such as Pb2+, Sn2+, and halogen ion such as Br-, Cl-, I- are used as A site, B site, and X site respectively.


Pic.1 Pe-QDs dispersion liquid
In the conventional QD, emitting color is controlled by its grain size. On the other hand, in case of PeQDs, it's possible to control emitting color by not only its grain size but also composition of X site. Concretely, blue and violet, green, and red are emitted by use of Cl, Br, and I respectively as X site. Emitting color can be determined at will by these parameters. As a result, margin of grain size distribution is enlarged. In a word, it's not necessary to control grain size uniformity severely at manufacturing process of PeQDs.

This PeQDs are emitted by absorption of UV light. Its photo luminescence quantum yield (PLQY) of RGB colors are 100 %. And also, in same as the conventional QD, sharp spectrum can be obtained by narrow half maximum full-width (20 - 45 nm). In the present moment, it's coated by various coating methods, but can be printed in the near future by the ink-jet printing method.


Fig.1 Picture and structure image of FTFR
It's mainly useful for wavelength conversion film and color filter of LCD. In short, conversion property is effectively used, concretely, it's emitted by absorption of UV light with shorter wavelength than that of PeQDs. For this reason, B-light is converted to G and R colors. As a result, G and R color plane lighting film is realized by use of B-LED. It's greatly effective for vegetable farming. If G-film is set at roof of a plastic greenhouse, UV light in solar can be converted to a pacific wavelength. As a result, food value and yield of vegetable can be improved.

In case of the latter, G dot and R dot are patterned by use of PeQDs, on the other hand, B dot is not patterned (blank). As a result, B light of B-LED is transmitted in front without change, on the other hand, it's converted to G and R colors in G and R sub-pixels. In short, device is composed of B-LED backlight, LC cell, and PeQDs-CF.

Ise Chemical is supplying a PeQDs dispersion liquid as sample in the present moment. And also, the company developed mass siesizerd method, which was named as FTFR (Forced Thin Film Micro-reactor). As a result, it's possible to mass-produce at 5000 mL/h.

Really wearable OLED lighting device is realized by builting in ultra-slim battery


Pic.3 Reverse side of ultra-slim OLED lighting device with slim battery cell

Pic.2 Pilot-produced OLED samples
On the other hand, Nippon Shokubai exhibited various flexible OLED lighting devices, such as roll type, curved type with PET substrate, and passive matrix display with glass substrate. They are composed of cathode/electron injection layer (EIL)/electron transport layer/emitting layer/hole transport layer/hole injection layer/anode. In short, device is an inverted structure using originally organic and inorganic hybrid layers as EIL instead of alkali series material. Its lifetime is superior because of high gas barrier property due to original EIL. In the present moment, current efficiency and lifetime (half brightness life) are 5 mA/cm2 and 100,000 h respectively.

In this time, an ultra-slim lithium ion battery cell "EnerCera (NGK Insulators)" was mounted on reverse side of OLED module due to realization of wearable property. As a result, total thickness was reduced same as 0.55 ㎜. In a word, it can be worn easily.

By the way, the company will construct mass production structure by the end of the year, and released at 2024.

Contact angle is increased and slit drop property is control by ultra-hydrophobic technology

With respect to manufacturing infrastructure, Citizen Watch appealed an original ultra-hydrophobic treatment technology. As figure 2, polydimethylsiloxane (PDMS) is treated to ultra-hydrophobic state by fine structure using patterned laser irradiation and nanoimprinting. Typical contact angle of water is increased to approximate 150 degree.


Pic.4 Comparison of hydrophobic property
　　　light:PDMS substrate left:ultra-hydrophobic PDMS substrate


Fig.2 Process flow of ultra-hydrophobic substrate
In this technology, it's possible to control slip drop property by devising dimension and arrangement of fine structure pattern. In a word, slip drop property from PDMS substrate can be controlled. As picture 4, the conventional PDMS substrate and this ultra-hydrophobic PDMS substrate were exhibited in the booth, and also, they were dropped with water. In the former, after enlargement of droplet, it was dropped at one time：on the other hand, in the latter, it was dropped at real-time. Of course, it's possible to control same slip drop property as that of the conventional PDMS substrate, too.

By the way, main applications are considered to be micro flow channel, precious mold, medical systems, and so on.

Structure of perovskite solar cell is simplified by use of CNT sheet as anode

As regards manufacturing process of perovskite solar cell, Zeon proposed that a single wall carbon nano tube (CNT) sheet was used as anode. As figure 4, CNT sheet is directly laminated on perovskite layer as anode. As a result, device structure can be simplified by unnecessary of hole transport layer and evaporated anode. For this reason, manufacturing process cost can be reduced, too. Furthermore, corrosion does not occur because of resolution-free of halogen element.

IPCE (incident photon-to-current efficiency) of the latest device is 18 % at interior, and 11 % at outdoor environment. In short, it is lower than that of the conventional device. For this reason, carrier injection height of perovskite layer and CNT sheet should be reduced in practical use. By the way, it's necessary to form a gas barrier film on CNT layer because of porous property of CNT.


Fig.3 Structure of the conventional device and proposed device using CNT sheet


Clay material is swept and coated as gas barrier film

As concerns gas barrier film of organic device, Kunimine Industries appealed a clay gas barrier material "Kunipia-RC series", which was produced at outsourcing from National Institute of Advanced Industrial Science and Technology (AIST).

It's a paste inclusive of main clay composition at 20 - 60 % concentration. It's solved into acetonitrile, ethanol, and 2-propanol, and then, coated on the substrate and dried at 100 ℃. In this coating process, montmorillonite crystals with plate shape crystal are selectively oriented by sweeping coating such as cast coating method and slit coating method.

As figure 4, impurities such as H2O and O2 are blocked by stack of this clay crystal. However, water-vapor transmission ratio (WVTR) is approximate 10-2g/m2/day, which is insufficient for organic device. For this reason, it's necessary to stack this film and inorganic film such as SiN series film.


Fig.4 SEM image of clay gas barrier film and generation mechanism of gas barrier property


Film with ultra-high gas barrier film is useful for perovskite solar cell

Toray announced to develop a barrier film with ultra-high gas barrier film, which was evaporated, for perovskite solar cell, various sensors, and so on. In this film, some inorganic compounds are co-evaporated. Its manufacturing cost is 1/5 than that of the conventional sputtering coated film because of ultra-high speed deposition and R2 process.


Pic.5 Film roll with gas barrier film by evaporation at ultra-high speed
WVTR is 10-3g/m2/day. If 2 films are laminated on top and bottom of perovskite solar cell at sandwich shape, practical gas barrier property is considered to be obtained. And also, basic characteristics such as flexibility (R=3㎜), transmittance (90 %), and haze (1 % and under) are almost sufficient as transparent film.

Polythiophene series polymer is used for conductive material and paint of flexible product


Pic.6 Pilot-produced transparent heater by coating transparent organic conductive material
As to transparent conductive material, Iwatsu Chemical Cross proposed to use a polythiphene series organic conductive material for transparent conductive film and paint. It's easy to correspond to flexible products compared to the conventional ITO film. Of course, after curved calibration and stretch calibration, initial conductive property is not degraded. Typical sheet resistance is approximate 200 Ω/□, but it can be adjust to some extent by concentration of liquid. Its transmittance is 85 - 90 %. Of course, sheet resistance and transmittance becomes with relationship of trade-off.

In the booth, tray for prevention of static charge, transparent heater, and film for liquid crystal shutter using this material were exhibited. It was indicated to be adopted for mass use yet.

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