Listen to a Report 丨 Dr. Xiao Yiming: Visionox's ViP Technology Will Push AMOLED Industry to the Next Level

Author:     Release Time: 2023-05-26

On May 21, 2023 (local time), the SID Display Week 2023 kicked off in Los Angeles. Visionox's first ViP-based flexible innovative terminal that can be folded with a bending radius of only 2mm made its debut overseas. During the event, Dr. Xiao Yiming, R&D Director of Visionox, was invited to deliver a speech about OLEDs, titled Development of Visionox intelligent Pixelization (ViP™) Technology in AMOLED Applications. His papers were also rated "excellent" and included in the SID Digest.

Since AMOLED was initially available for small-size mature applications and then for "micro, small, medium, and large-sized" applications, the performance of AMOLEDs needs further improvement to adapt to multiple applications. For example, improvements shall be made to the ultra-high resolution of micro displays, the brightness and lifetime of large-size displays, etc. However, these performance improvements are hindered by bottlenecks caused by the physical limitations of the FMM.

Visionox's ViP technology can significantly improve the performance of AMOLED products and fundamentally solve FMM-related problems in the manufacturing process. Consequently, it will push the AMOLED industry to the next level. Dr. Xiao Yiming, who was invited to give a speech about OLEDs, said that ViP technology breaks through FMM bottlenecks, such as precision limitation, low material utilization rate, single panelization, high tooling cost, and long development and production cycle. He also introduced seven advantages of ViP technology, including no FMM, high precision, and independent pixels.

"Independent pixel" means that many common layers are inserted in an FMM AMOLED device, serving all R/G/B pixels at once. However, ViP AMOLED pixels are photoetched, enabling the independently tunable AMOLED device structure with different colored pixels.

Better Visual Performance 

For sub-pixels with each color, all EL films, cathodes, and CVD packaging layers closest to the device can be fully customized according to the characteristics of RGB color, to enhance microcavity gain. This allows for a better balance between EL device efficiency and brightness decay. ViP AMOLED can achieve a JNCD of less than 1.0 at an angle of view of less than 75°; compared with FMM AMOLED, the EL device can achieve a 6.5% reduction in power consumption (it is derived from computer simulations).

Shorter Product Development Cycle

Independent R/G/B pixels can not only optimize the performance of independently tunable EL devices but also shorten the development cycle of OLED materials. The development of EL devices for FMM AMOLED starts with the B pixel device and proceeds to the R/G pixel device after determining the common layer material. However, the EL device for ViP AMOLED is not subjected to the common layer, and R/G/B pixel devices can be developed in parallel. Therefore, the total development cycle of EL devices can be shortened (by up to 30%, based on Visionox's experience).

Better Image Quality at Low Grayscales

ViP's unique structural design renders each sub-pixel independent, and the pixel-level isolation structure cuts off the current transmission path that leads to crosstalk in AMOLED displays. At present, flagship FMM AMOLED can achieve about 87% DCI-P3 gamut coverage at low grayscales (e.g. 2nit 48 grayscale), while ViP AMOLED can keep the same DCI-P3 coverage as at high grayscales, reaching over 100%.

Higher ppi and Aperture Ratio

Not using FMM, ViP technology is not subjected to ppi limitations and can achieve higher ppi. The PDL gap of ViP AMOLED can easily reach 10μm and can be reduced further to 8μm, reaching the highest pixel density of 1,500ppi (It is calculated when the paper is submitted and is further upgraded to 1,700ppi during subsequent process improvements). In this way, ViP AMOLED applications can enjoy an extension to near-to-eye display devices such as AR/VR. For products that demand a conventional ppi, the aperture ratio of ViP AMOLED will be boosted by reducing the PDL gap, which leads to great increases in the lifetime and JNCD of AMOLED.

Better Brightness Uniformity and Lower Power Consumption

FMM AMOLED is designed with thin cathodes and high resistance, resulting in severe IR-drop and uneven distribution of ELVSS potential in the AA region. To solve this problem, FMM AMOLED usually adds a certain buffer to the voltage and uses an IC with an IR-drop compensation function. Nevertheless, these measures could generate extra power consumption. In addition, the current varies with OPR (On Pixel Ratio), which leads to different ELVSS drops and causes differences in brightness. However, in ViP AMOLED, a metal mesh structure is formed by the isolated column structure around each pixel, which greatly reduces ELVSS access and routing resistances. Therefore, ViP technology solves the above problems caused by the high cathode resistance in FMM AMOLED with higher brightness uniformity and lower power consumption.

High brightness uniformity and low power consumption are of instrumental significance for large- and medium-sized AMOLED displays.

Higher Transmittance

Compared with FMM AMOLED, in areas where high transmittance is required (such as the second screen area of the display screen with an under-display camera), the transmittance of the display screen is reduced because of layer stack-ups and metal films (such as cathodes). Furthermore, the under-display camera gets a good tradeoff between display and transmittance through technologies, such as "serpentine electrode routing" and "edge-mounted circuit" pioneered by Visionox. However, metal routing inevitably passes through high-transmittance areas. These routings would form pinholes when passing through light holes, resulting in strong diffraction and reducing the image quality of optical sensors, such as under-display cameras, to some extent.

Because the ViP-based EL device is patterned using a photolithographic process, useless films (e.g. cathode and EL film) in high-transmittance areas can be removed to improve transmittance. In addition, the ViP-based unique structure can cover the pinholes caused by metal routing, which will reduce pinhole diffraction and improve the image quality of under-display sensors, such as under-display cameras.

More Flexible Production and Delivery

The replacement of FMM by ViP can solve problems, such as high template design cost and long template production and delivery time with lowered minimum order quantity. The ViP process can achieve the target shape through photolithography and customize the panel shape based on customer requirements. It also enables more compact and economical panelization on a glass substrate of the same area to increase utilization.

During his speech, Dr. Xiao Yiming said the new ViP technology brings higher performance to meet higher product requirements, that is, by improving display performance and shortening delivery time, consumer electronics terminal manufacturers can obtain more innovative and competitive products.

Every year, the SID event sets up various technical sessions to conduct in-depth discussions on the status quo, difficulties, and cutting-edge trends in the field of technology, with speakers from leading enterprises or research institutions in this field. In addition to the ViP report, Visionox was also invited to give a speech on its dual-band dual-polarized 5G millimeter-wave antenna-on-display.