CEATEC 2022 IGZO-TFT E-Paper and perovskite solar cell are popular

October 18 - 21, CEATEC 2022 were held in Makuhari Messe. Main topics are closed up in this here. By the way, the online exhibition is opened on the official homepage (https://www.ceatec.com/en/) until October 31st.

As concerns display, Sharp and E Ink Holdings appealed to collaborate with IGZO (InGaZnO) -TFT backplane for microcapsule type electrophoretic display, and exhibited 8-inch 300ppi full color panel as a prototype.

As you know, E Ink developed a new coloring method in 2018. In this method, Y (yellow), M (magenta), C (cyan), and W (white) coloring toners are used, and they are filled into micro-capsules. Display mechanism of this panel is same as that of the conventional monochrome panel; however, gay scale is controlled by stacking level of toners in the front electrode, which is determined by applied voltage. In short, charge level of toner is controlled with respect to each color because of different threshold voltage. Of course, if white is displayed, W toner is adhered to the front electrode, on the other hand, if black is displayed, 3 toners (Y, M, and C) are adhered to the front electrode.

Pic 1. E-Paper by IGZO-TFT driving

As a result, number of colors is increased same as 32,768 (32 gray scale). By the way, that of the conventional micro color filter (CF) panel is mere 4096. And also, brightness is approximate double compared to CF panel because of without black toner, absorbs reflect light. Of course, opening ratio, in short, actual light utilization efficiency is increased because display mechanism is not based on spatial segmentation method such as CF panel.

However, response speed becomes to be slower because of its display mechanism, and rewriting time was about 15 sec. For this reason, E-Ink changed driving method from a-Si TFT to IGZO (InGaZnO) -TFT, which had high carrier mobility. As a result, driving voltage can be highly applied. Therefore, it's possible to rewrite monochrome image for 0.35 sec, and color image for 0.5 - 1.5 sec.

Sharp will supply IGZO backplanes to E Ink from now.

Kyocera exhibits an originally aerial display system

On the other hand, Kyocera exhibited an aerial display system, which was originally developed.

Pic 2. Aerial display system

Its system is composed of TFT-LCD panel and 2 original mirrors. As its name, in this system, displayed image seems to be floated from viewers. Furthermore, it's possible to operate floated image by touch operation because of use of motion sensor. In this time, 6-inch image was displayed, however, large size and high resolution image can be displayed by making use of TFT-LCD panel with same size and resolution.

Medical system, amusement system, exhibition display, and dashboard of automobile are considered to be useful as its applications. The company will release this system oneself at 2026.

Toshiba brushed up perovskite solar cell using plastic substrate

With respect to perovskite solar cell, Toshiba exhibited a real flexible device with PET plastic substrate unlike in last year (online exhibition). Its IPCE (incident photon-to-current efficiency) was enhanced from 15.1% to 16.6% in this year. Furthermore, device size was enlarged to 703 cm². However, release time will be 2025.

Most feature is an originally developed coating technology (the meniscus coating method) of perovskite (PVK) layer. Figure 1 shows its process. It's possible to uniformly coat PVK ink on a large substrate by making use of surface tension of ink.

In the past, the company coated PbI ink, and dried, the next, coated MAI ink, and dried. In short, crystal MAPbI3 was obtained by 2 step process. In this time, 1 step process was developed. Concretely prepared MAPbI3 in advance is coated with control of crystal growth by the meniscus method.

Figure 1. Image of meniscus coating

The company previously developed a two-step coating process that first applied a layer of PbI2 (lead iodide) ink to a substrate, followed by a layer of MAI (methyammonium iodide, CH3NH3I) ink, triggering a reaction that formed an MAPbI3 layer. However, this multi-step approach had a low coating rate and often left unreacted sections in PVK layer. The alternative is a one-step process that applies MAPbI3 ink directly, but it is not easy to control crystallization of the MAPbI3 and obtain a uniform PVK layer across a large area. A new coating method that solves these problems was required.

Sharp exhibited a flexible perovskite solar cell for the first time

By contrast, Sharp exhibited a perovskite solar cell in the first time, and announced to release as a flexible solar cell in the near future.

Pic 3. Film-based perovskite solar cell

As you know, the company has released dye-sensitized solar cells (DSC) yet. For this reason, the company selected the meso-porous type, which was created from DSC. Concretely, device is composed of transparent anode/electron transport layer (ETL)/porous ETL + perovskite layer/hole transport layer/metal cathode. Perovskite material is sorbed into porous electron transport layer. This is reason why moving length of electron in perovskite can be reduced. As a result, IPCE is increased.

As picture 3, 30 × 30 cm module was exhibited with PET film. However, its IPCE was not disclosed because of first prototype. The company will release the device in 2024 - 2025.

Micro Technology appealed ultra-thin glass with patterned electrodes

Pic 4. Ultra-thin glass samples with some electrodes

As regards material, Micro Technology exercised presence. Main exhibit was ultra-thin glasses with patterned electrodes. Their thickness can be adjust at will, for example 0.05 - 0.2 �o by wet etching technology using hydrofluoric acid. Its maximum size is 730 × 920�o.

Of course, the company supplies this ultra-thin glass with some patterned electrodes. In the booth, soda lime glass samples (200×200�o) with Ti/Cu seed layers and patterned Cu electrode were exhibited. As picture 4, it's possible to curve easily in case of 0.05 �o thickness.