In the last couple of years, consumers are hearing about this newfangled display technology called OLED. OLED (Organic Light Emitting Diode) is considered as the future of flat panel display. Is it really?
A brief history
First of all, allow me to straightened the misinformation about the “newness” of OLED. The basis of technology itself have actually been around since the 1960’s by Martin Pope and some of his co-workers at New York University when they developed ohmic dark-injecting electrode contacts to organic crystals. The display application, however, was done on the Canadian side in 1965. W. Helfrich and W. G. Schneider of the National Research Council in Ottawa produced double injection recombination electroluminescence for the first time in an anthracene single crystal using hole and electron injecting electrodes, which is the forerunner of modern OLED TV.
How it works
A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a layer of substrate. The organic molecules are electrically conductive. These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductors (the “Organic” part of “OLED”). Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer. The structure which have been around since 1965, thanks to both Canadians mentioned above.
Of course these OLEDs need to be applied on something. For a high resolution display like a TV, an amorphous-silicon/microcrystalline-silicon backplanes are used to manufacture large-sized displays whereas for a small-sized displays such as mobile phone screens, Low Temperature Polycrystalline Silicon Thin-Film Transistor (LTPS TFT) is used. As for the front, a plastic material called PET (Polyethylene Terephthalate) is used to seal and protect the OLED material from dust and moisture.
According to “IEEE Transactions on Components, Packaging and Manufacturing Technology” released in 2011, transfer-printing is the choice technology to assemble large numbers of OLED and devices efficiently. How does it work? The following is the quote from the above white-paper: “It takes advantage of standard metal deposition, photolithography, and etching to create alignment marks commonly glass, or other device substrates. Thin polymer adhesive layers are applied to enhance resistance to particles and surface defects. Microscale ICs are transfer-printed onto the adhesive surface and then baked to fully cure adhesive layers. An additional photosensitive polymer layer is applied to the substrate to account for the topography caused by the printed ICs, reintroducing a flat surface. Photolithography and etching removes some polymer layers to uncover conductive pads on the ICs. Afterwards, the anode layer is applied to the device backplane to form bottom electrode. OLED layers are applied to the anode layer with conventional vapor (sic) deposition, and covered with a conductive metal electrode layer.”
In other words…it’s a hyper complex manufacturing process and because of its complexity, this is why we didn’t hear large-sized OLED until a couple of years ago.
Advantages of OLED
Due to the nature of emissive display where each and individual sub pixel can be controlled individually, the potential for better accuracy is much higher on an OLED display. This can not be achieved by transmissive display technology without various complex and fragile technological band aids such as Quantum Dot, colour filters, special glass and coatings which will ultimately can only be applied to higher prices TVs.
In a transmissive display technology, the only way to achieve true black is by turning off the backlighting of the LCD panel. It is an acceptable solution but even at the very best, currently the TV can only dim up to 640 zones whereas in OLED the display can shut off each pixel individually…in the case of 4K TV…4 million zones!
For the time being, OLED is actually not more expensive than LCD displays of the equivalent quality. In the future OLED will definitely be more affordable. However, to achieve a similar quality to OLED, the price for an LCD will remain the same due to the amount and cost of band aid technologies needed to be utilized.
Image Retention and Burn In
I have not yet had the chance to “ruin” an OLED TV, but from playing back 2.35:1 image ratio on my first generation OLED more than 90% of the time (and the OLED TV have now clocked more than 1,000 hours), I have yet to see any image retention caused by the black bars. On the other hand, when I go to Las Vegas for CES or Denver for CEDIA, I always see burned-in image on the airports’ LCD panel. My point is, unless you deliberately want to create image retention, with either technology, it’s very difficult to do so.
Refresh rate is directly correlated to a display’s response time. OLEDs have a much faster response time than an LCD. Using response time compensation technologies, the fastest modern LCDs can reach as low as 1 ms response times for their fastest color transition and are capable of refresh frequencies as high as 144 Hz. According to LG, their 2014 OLED response times are up to 1,000 times faster than LCD putting conservative estimates at under 10 μs (0.01 ms), which in theory could accommodate refresh frequencies approaching 100 kHz (100,000 Hz). Due to their extremely fast response time, OLED displays can also be easily designed to be strobed, creating an effect similar to CRT flicker in order to avoid the sample-and-hold behavior used on both LCDs and some older (pre 2014) OLED displays that creates the perception of motion blur.
Unlike regular LCD, OLED have a true 178-degree viewing angle which means as long as you can see the picture shown on an OLED, you will have the same colour rendition. With LCD, even in the best case scenario, you can only get a maximum of 90-degree viewing angle while maintaining colour rendition without any colour shift.
The Disadvantages of OLED
This is where LCD shines (literally). As there is no need for each individual sub pixel to light itself, the backlights of an LCD can be boosted to any level the manufacturers feel like. However, considering the recommended brightness level set by THX is 35 fL (foot-Lambert) and even a 30 year-old tube TV can achieve that brightness without any problem, except for outdoor applications, why would anybody need super-duper-brightness level? So yes, it is not as bright as LCD, but it can yield brightness far higher than recommended anyway, thus making this disadvantage a moot point.
With LCD, you usually get between 60,000 to 100,000 hours of full lifespan although I don’t quite understand where the manufacturers get those numbers as I have yet to witness an LCD panel that lasted longer than 20,000 hours…and I do witness a LOT of LCD displays. On the other hand, OLED “only” have the lifespan of 40,000 to 70,000 hours. Once again, it is a moot argument as if you watch your TV for 8 hours a day, every day, for almost 14 years, you will only hit the 40,000 hour mark.
With so many advantages and only two non-disadvantage disadvantages, OLED is a clear winner regardless how you want to slice it. Yes it is going to cost you around $10,000 for a 65” Premium UHD OLED…but it will also cost you around the same amount of money to buy a comparable (not quite, but you know what I mean) LCD TV with full-array backlight system…so why buy LCD?