OLED is an emerging display and lighting technology that enables beautiful and efficient displays and lighting panels. Thin OLEDs are already being used in many mobile devices and TVs. Polymer-OLEDs (or PLEDs, also used to be called P-OLEDs) are OLED devices made from polymer (large-molecules) materials.
PLEDs vs SM-OLEDs
Basically you can make OLEDs from two kinds of materials: small-molecule (SM-OLED) or large-molecules, or polymers. Virtually all OLED displays on the market toady are using Small Molecules, and are produced using evaporation processes.
PLED (P-OLED) materials do not perform as good as SM-OLEDs in terms of lifetime and efficiency, but are easily soluble and so can be easily adapted for printing and other solution-based processes. In the past some believed that the soluble nature of PLEDs mean that these materials will be the future of OLED displays, but that has not been the case yet. There has been great progress in evaporation processes and materials - and also in soluble SM-OLEDs.
CDT / Sumitomo
UK-based Cambridge Display Technology (CDT) is the company that holds the basic patents for PLED technologies. The company licensed its technology to several companies, including Philips, Seiko Epson, Osram, Dupont and Delta Optoelectronics, but it does not seem as it anyone is pursuing PLEDs at the moment besides Sumitomo Chemicals (which owns CDT).
Sumitomo and CDT are still developing PLED materials and panels. Sumitomo is providing emitter materials for JOLED (who started low volume production of printed OLED monitor panels in December 2017, see below) and is hopefully gearing up to start mass production of its own OLED lighting panels.
JOLED (Japan OLED) was established in August 2014 by Japan Display, Sony and Panasonic with an aim to become an OLED medium display (10-30 inch) producer. JOLED is using a printing process which should result in lower cost production (but of lower performance displays) compared to evaporation printing.
JOLED is using PLED materials produced by Sumitomo (see above). The company started commercial low-volume production of its 21.6" 4K OLED panels towards the end of 2017 at the company's pilot 4.5-Gen line. JOLED has announced plans for a mass production 5.5-Gen line that will be established in Nomi City, Ishikawa Prefecture, by 2020.
Panasonic's 2013 56" OLED TV prototypes
In January 2013 Panasonic unveiled a 56" 4K (3840x2160) OLED TV panel prototype that was produced using an all-printing method and PLED materials. Panasonic says that all the organic materials were deposited using ink-jet printing. The panel's TFT substrate was supplied by Sony (and actually made by AUO. It's an Oxide-TFT panel) as part of the two companies collaboration. The lifetime and efficiency of this TV was not disclosed.
In December 2013 Sony and Panasonic announced that they are canceling the OLED TV JV. Panasonic is now producing OLED TVs - but these use WRGB OLED panels produced by LG Display.
PLEDs in the market
In the past, several PMOLED makers produced PLED based small-sized display modules, mostly alpha-numeric and single-color panels. As of 2018, PLED PMOLEDs are not in production any more.
PLED PMOLED module (OSD)
P-OLED (PLED) vs pOLED
P-OLEDs, or PLEDs, are a class of OLED materials. Somewhat confusingly, LG Display is branding its mobile flexible AMOLED displays as pOLEDs (plastic OLEDs). For more information on LGD's pOLEDs, click here.
The latest PLED news:
Researchers from the Imperial College London developed a new class of PLED materials that exhibit circularly polarized luminescence. Basically this means that the new materials emit polarized light which could make for more efficient Polymer-OLED devices as none of the light will be blocked by the external anti-glare circular polarizer added to the display.
In 2013 researchers from the ICL has reported they are researching the usage of Helicenes as emitter materials in PLED devices that also emit circularly polarized light - the researchers termed these devices CP-OLED (Circularly-Polarized OLED). Helicenes materials are thermally-stable polycyclic aromatics with helically-shaped molecules.
At the OLED Korea conference, both Merck and Sumitomo detailed their latest OLED inkjet material performance.
Researchers from Sweden's Chalmers University have developed a new "double doping" process that basically doubles the efficiency of Polymer OLED emitter materials.
The researchers explain that doping in organic semiconductors operates through what is known as a redox reaction, in which the dopant molecule receives an electron from the semiconductor which increases the electrical conductivity of the semiconductor. The efficiency limit of current doped organic semiconductors has been limited by the fact that each dopant molecule was able to to exchange one electron only. In the new research it was shown how it is possible to move two electrons for every dopant molecule which increases the conductivity of the organic material.
Researchers from the University of California Berkley developed a new flexible and lightweight blood oxygen sensor that can map oxygen levels over large area. The sensor uses an array of red and near-infrared OLEDs, together with organic photo-diodes, printed on a flexible substrate.
The research was supported by Cambridge Display Technology, which means that these red and near-infrared printed OLEDs use polymer emitters (PLEDs).
Many OLED producers believe that Ink-Jet printing of OLED emissive materials is the best way to achieve lower-cost OLED TV production, and to enable OLEDs to compete in the medium part of the TV market. Ink-Jet printing is an efficient process (less material waste compared to evaporation) and it can be very quick as well. The main drawbacks of inkjet are the limited resolution and the need for soluble emissive materials which are less efficient compared to evaporation ones.
A Kateeva OLED ink-jet printing system
These challenges are being overcome, and it seems that at least four groups (in Korea, Japan and China) are charging forward towards mass production of ink-jet printed OLEDs. Ink-jet printer makers and soluble material suppliers are also optimistic ink-jet printing commercialization will soon be here as the material performance gap is diminishing.
A few day go JOLED announced that it started commercial shipments of its 21.6" 4K OLED panels for use in medical monitors, in its low-volume 4.5-Gen ink-jet printing production line.
Following JDI's decision to halt its plans to increase its stake at JOLED, the company is now seeking to raise $900 million to support its plan to start mass producing OLEDs in 2019. According to a report from Japan the company has received commitments from Sony and Panasonic and both Sumitomo Chemical (who supplies its PLED materials to JOLED) and Screen Holdings (who supplies its equipment to JOLED) are likely to take part in the financing round as well.
In June 2017 JOLED announced that it started to sample 21.6" 4K OLED panels, with plans to initiate low volume production at its 4.5-Gen pilot inkjet production line. JOLED announced today that it has began commercial shipments of these panels. We do not know JOLED's first customer but it is likely to be Sony.
JOLED says that it has now achieved the necessary product quality and production yields. The product was already selected for use in medical monitors (again, we believe this is Sony, who we know received JOLED's first samples and already has its own 25" OLED medical monitor that uses Sony's own OLEDs). JOLED also aims to ship these panes to other OLED monitors applications.
Sumitomo Chemical acquired CDT back in 2007, and since then the Japanese company has been developing it's PLED (polymer-based OLED) materials and technologies. While initially Sumitomo aimed to produce materials for displays, in recent years it has focused mostly on OLED lighting materials and even panel production.
A noted exception was Panasonic's OLED TV development project which used printing technologies and Sumitomo's PLED materials. But Panasonic terminated this project in 2013. We speculated that JOLED, which is based on Panasonic's technology (and other technologies as well), uses PLED materials in its prototypes, but we were not sure.
Researchers at the University of California, Santa Barbara and the Dow Chemical Company have chosen a bottom-up approach to patterning emissive polymers, aiming to solve some of the problems that plague Solution-based protocols for OLED manufacture.
The team started with a layer of indium tin oxide and used light-activated chemistry to pinpoint specific locations on the surface for polymer growth. Key to the success of this approach are designer iridium photocatalysts that serve two roles: First, as the catalyst to build the emissive brush polymers, and then as a necessary dopant for the resulting OLED arrays.
Researchers from the Technical University in Dresden have developed a method to produce polymer TADF emitting molecules. Up until now most TADF materials are based on small molecules or chromophores linked to a polymer network.
This research focused on actual polymer TADF, and using a controlled extension of the conjugation of the monomers HOMO wavefunction, the researchers were able to to increase thephotoluminescence quantum yield from about 3% to about 71%. The reseachers say that this is an encouraging first step towards polymer TADF emitters.