WOLED display with a-Si backplane
Among those things that are accepted in the display industry, one of them is that a-Si (the standard backplane for 75% of the display industry) is not just not stable enough to drive AMOLED displays. AUO tried in 2003 and offered an RGB demo but ultimately failed. Since then, the more complex and expensive IGZO and LTPS-based backplanes have become the norm for large displays and mobile displays, respectively.
This convention has now been overturned by the work of a 3-year-old start-up called Mattrix Technologies, a University of Florida spin-off and one of my clients (IC08 Mattrix is the new NVerPix – with new switches) . As far as I know, this is now a world first – a lower emission white OLED display with a-Si as a switching transistor. The pixels in this full-color demo are based on Mattrix’s SHUTTER technology, a vertically arranged three-terminal device that combines drive-TFT, storage capacitor, and OLED, and a very different take on backplane designs. TFT used in today’s AMOLED displays. .
So what are the benefits of this technology I hear you ask? Well several times. First, there is a reduced cost for the backplane needed to drive the OLED. The technology uses the cheapest semiconductor process (a-Si), but also drastically reduces the complexity of the compensation circuit. Second, the current density in the vertical channel is 2-3 times lower, which widens the design space so as to improve the service life or make the screens brighter. The vertical channel also decouples the current path from the gate-oxide interface, reducing image burn-in.
Emissive apertures, as relevant in bottom emitting devices, are also improved. The technology makes it possible to use or build cheaper factories, as the expensive, high masked backplanes can now be replaced with something significantly cheaper. There is less opex in the fab and this allows older a-Si fabs, from Gen 4 to Gen 10, to be reused (with a new frontplane) as OLET fabs.
The net present values (NPV – today’s value of a longer term investment – publisher) of new OLED manufacturing projects of all types are also significantly improved. It’s a win-win solution for old and new factories. All fabulous. The technology is ideally suited for emissive TV technologies and replacing LTPO for mobile applications, as you get the capabilities of low-power display technology with refresh rate management options.
The “secret sauce” is in multiple areas, from a proprietary nanocarbon source electrode (materials supplied by JSR Corp.) to a slightly different driving method and the SHUTTER structure itself. A cross-sectional image of the SHUTTER architecture is shown in Figure 1. Not only is the architecture fully compatible with a wide range of self-emissive materials, from phosphorescent OLEDs / solutions, and TADF to QD OLED and QDEL, but a key point is that it can be implemented with existing equipment and processes in all display configurations: both top and bottom transmission; WOLED + CF, RGB FMM and RGB IJP.
The demonstrator itself, as shown in Figure 1 below, is a 4.7 inch WOLED panel manufactured by Mattrix on a conventional LCD backplane supplied by a Japanese subcontractor. It has a brightness of 500 cd / m² and a resolution of 85 dpi (demo TV). The increased panel aperture ratio results in a> 250% increase in lifespan compared to OLED control devices.
It is remarkable that a demonstration of this quality can be performed on a small, outsourced, completely conventional a-Si line with off-the-shelf materials (relatively mid-range, non-proprietary OLEDs) without any mura correction or pixel compensation. .
Implications of STREAM development
This technology radically simplifies the production of AMOLED and improves the performance of the product. So far, backplane yield losses have been perhaps 40% of the overall yield challenge in OLEDs: this makes a drastic difference, as we would now expect a-Si type yields instead. in the backplane.
In my opinion, this technology makes LTPS less important. This makes IGZO less important. It allows companies with only basic a-Si capabilities and older factories to compete with AMOLED. This radically changes the economics of new and old factories in AMOLED: as a result, we might expect more AMOLED devices and faster conversion of price-sensitive computing categories such as tablets and laptops. The implications, if adopted, could be very changeable for the industry.
Granted, this is a very interesting development and while mass production may still take a few years, it is something we should all watch out for as a new strategic option for the OLED industry. (IH)
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Ian Hendy is a poster strategy consultant based in London, UK. Hendy Consulting provides growth strategy, technology strategy, and deal / M&A assessments for players along the display value chain. Mattrix is a client of Hendy Consulting.
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