Televisions have evolved rapidly over the past few years - we've seen smart functionality, 4K Ultra HD resolution and HDR all become established features. OLED technology has also managed to work its way on to the long list of TV jargon, with its main selling point being ultra-dark blacks (surpassing those previously seen on plasma TVs) and super-punchy contrast.
But it hasn't been a smooth ride for OLED since then. First, there was news that Sony and Panasonic had ended an OLED TV production partnership in order to focus on Ultra HD LCD TV production, and in 2015, Samsung decided to ditch OLED and concentrate on 4K LCD screens, leaving LG as the sole manufacturer of OLED screens.
Fast forward to 2017, and we now have seven TV manufacturers with OLED sets in their TV line-up: LG, Panasonic, Sony, Philips, Toshiba, Bang & Olufsen and Loewe. They still source all the panels from LG Display, who remain the only company actually producing OLED TV panels.
Samsung, meanwhile, is backing a different horse when it comes to TV tech: QLED. Don't confuse QLED with OLED, though - they're two completely different TV technologies. Samsung does produce OLED screens, quite a lot of them in fact, but only for mobile devices - like the new iPhone.
But what's all the fuss about OLED anyway? How does OLED technology work, what's so good about it and which are the best OLED TVs to buy? Let us explain.
What is OLED?
OLED – Organic Light-Emitting Diode – is a type of display technology that makes it possible to reach dark blacks and build ultra-thin televisions, while at the same time making them more efficient and eco-friendly.
Here’s how OLED technology works: an organic, carbon-based film is placed between two conductors, and when an electrical current is passed through, it emits light.
This process takes place in every single pixel in an OLED display.
This differs from an LCD (Liquid Crystal Display) panel, which requires a backlight (typically made of standard LEDs) to light up the liquid crystals and create an image. Not only does this require a lot of energy, you also don't get true blacks as the backlight affects neighbouring pixels.
On an OLED panel, the organic pixels are self-emissive, which means they generate their own light - and can go pitch black when each pixel is turned off.
There are two types of OLED technology: Passive-Matrix (PMOLED) and Active-Matrix (AMOLED). Active-Matrix requires electronics to switch each pixel on or off individually, which is better for displaying deep blacks, and therefore the type used for the OLED TVs we see today.
OLED pixels also include an additional white pixel alongside the usual red, green and blue sub-pixels, which aims to deliver more varied and accurate colours, as well as increasing a display's lifespan.
What are the advantages of OLED TV?
OLED technology has several advantages over LED-lit LCD TVs.
First, there's design – OLED sets are lighter and thinner than LCDs since they don't need a separate backlight.
To give you an example of just how slim, LG showed off an OLED display just 0.97mm thin back in 2015, while you can buy the more recent "Wallpaper" TV (the £8000 OLED65W7), which measures just 2.57mm. It's really very flexible.
But of greater interest is the picture quality. Because each pixel can be turned off individually, OLED TVs deliver absolute black and stronger contrast ratio – the holy grail for AV purists. We've seen this striking contrast and depth time and time again on OLED TVs such as the five-star LG OLED55B7V.
Since OLED pixels emit their own light and colour, viewing angles also tend to be much wider than LED-backlit LCDs: colour and contrast retain their intensity from as far as 90 degrees off centre.
And while Samsung's 2017 QLED sets are significantly brighter (the QE49Q7C reaches 1500nits), OLED panels are catching up. You can get 1000nits of peak brightness from a 2017 LG OLED (such as on the OLED65E7V), where previously it topped off at 800nits.
MORE: Sony KD-55A1 review
What are the disadvantages of OLED TV?
OLED is extremely expensive to produce, and consequently, OLED TVs are expensive to buy.
In its infancy, OLED production had a punishingly low yield rate, which meant that for every set fit for sale, a high number were consigned to the scrapheap. This made the technology expensive to produce - and this is one of the main reasons why you still don't see OLED TVs under 55in.
Another one of OLED’s problems concerns the pesky blue pixel. The organic material used to create blue light deteriorates more quickly than red and green, which means its lifespan is shorter and, over time, the colour balance could be affected, although we've never experienced any issues during our tests.
Thankfully, based on recent OLED TVs, the sets are definitely getting better - and more affordable.
More after the break
What about 4K HDR OLED TVs?
But with the advent of 4K Ultra HD resolution, it was only a matter of time before the two cutting-edge technologies were combined. LG introduced the first 4K OLED TV - the 55EG960V - in 2015, and since then it's become an incredibly impressive combination.
HDR (High Dynamic Range) isn't exclusive to OLED TVs, but it can make a huge impact on OLED's picture performance by displaying even greater variations in colour and brightness.
4K OLED TVs with HDR include the stellar Sony KD-55A1, the Panasonic TX-55EZ952B (whose HDR performance was the weakest link), while all of LG's 2017 OLED TVs come with Dolby Vision HDR support as standard.
There are even more 4K HDR OLEDs in the pipeline: we've seen Panasonic's flagship TX-65EZ1002 at CES 2017, Toshiba's first OLED, the 65X9863DB and the new Philips 65POS9603 at IFA 2017, as well as the BeoVision Eclipse - B&O and LG's joint offering that comes with a motorised stand and soundbar-like speaker.
What about curved OLED TVs?
Samsung and LG were the first to launch curved OLED screens. There's been a lot of scepticism over the curve - is it genuinely useful or is it just another gimmick?
We saw it as both a plus and a minus in our review of Samsung's first curved OLED TV. “It’s an outlandish idea,” we said, “not unlike a concept car: it’s very cool, even if it might not be entirely practical”. A curved set also can’t be as easily wall-mounted as a flat screen.
The argument in favour is that some people feel a curved set can enhance the viewing experience. Samsung has claimed in the past that it provides “depth to the content displayed for a more life-like viewing experience”, and delivers an “immersive panorama effect". LG has said the curve is there to “remove the problem of screen-edge visual distortion and detail loss”.
However, manufacturers' enthusiasm for curved OLED TVs has cooled somewhat in the last year, with flat OLED screens now dominating the market. At the start of 2017, LG and Sony announced they would stop making curved TVs, OLED or otherwise. Samsung is the only one still making curved screens for some of its 2017 LCD TVs.
What about flexible OLED TVs?
And if that wasn't enough from LG, the company has also been developing even more flexible OLED screens.
We've already mentioned the ultra-thin "Wallpaper" W7 range OLED, which sticks to your wall using magnets and wobbles a fair bit.
But LG has recently pushed the boundaries even further, creating an OLED panel that's transparent and completely rollable. This 77in screen can be rolled up into a tube just 8cm in diameter and is 40% transparent.
Don't expect to see these screens in the home just yet; they're designed for advertising purposes only.
LG has unveiled similar technology on a much bigger scale for advertising screens. And it's doubled its production of OLED and flexible OLED panels at the same time as increasing its investment, which should hopefully bring the price down for us punters.
Displays like the Wallpaper W7 and the roll-up TV might seem like a novelty, but we wouldn't be surprised to see some of that technology trickle down to consumer products in the next few years.
What are the alternatives to OLED TVs?
Quantum dot technology is the biggest rival to OLED screens, most notably Samsung's most recent variant, QLED.
QLED (Quantum-dot Light-Emitting Diode) uses tiny semiconductor particles only a few nanometers in size, which, in theory, emit their own light. It's based on existing quantum dot technology, where the bigger particles emit red light and the smaller ones do blue light, for instance.
In current TVs, however, they don't emit their own light, and need backlighting just like conventional LED-lit LCD panels do to create an image.
However, Samsung - who is the main proponent of this technology - claims its 2017 QLED screens will deliver all the benefits of OLED (deep blacks) but with much brighter whites (beyond 1500nits of peak brightness) and a 100% reproduction of the colour volume.
The QLEDs we've tested so far - the five-star QE55Q7F and the four-star QE49Q7C - deliver brilliant whites and superbly detailed colours, but they still can't quite reach the same black depths as an OLED. The QLED sets are almost as expensive as the equivalent OLEDs, too, despite quantum dot TVs being easier and cheaper to manufacture than OLED.
LG also previously promised a 4K quantum dot TV, but it's now planning its own version using Nano Cell technology. Unlike quantum dot, which uses different-sized particles, nano cell technology uses uniform particles of around 1 nanometer in diameter. LG claims this will result in more accurate colours and greater viewing angles - although we're curious to see how this will improve on LG's own OLED performance.
Chinese manufacturer Hisense has introduced its own take on the tech - ULED (Ultra LED) - which it claims can produce a picture quality as good as OLED but for much cheaper. We're not convinced, however, as the Hisense 65XT910 failed to impress us despite the £2200 price tag. And it seems Hisense agrees, as it's also planning to jump on the QLED bandwagon with Samsung.
What are the best OLED TVs?
Tested at £3500
Sony's first 4K OLED range is stunning. The 55in A1 is just as good as LG's 2017 OLED TVs and even has a unique sound solution. Is this the new benchmark for OLED screens?
Tested at £5000
Sure you can get smaller (well, 55in) LG OLED screens for cheaper, but this big 65in screen is a mighty fine option - if you can afford it.
Tested at £3000
Have your heart set on an LG OLED? This superb 4K OLED TV is arguably the pick of its 2017 range.
Tested at £2500
This Curry's exclusive is another appealing LG OLED set, and one of the most affordable one we've seen in 2017.
Tested at £3000
Panasonic's second 4K OLED range (also its most affordable) gets close to picture perfection, but is let down by its middling HDR performance.
Tested at £2800
Philips's first OLED set isn't the subtlest of performers, but OLED and Ambilight are a potent and immersive combination.
Tested at £2700
This was one of the most affordable 4K OLED TVs around in 2016 - it's still not cheap, but you get a lot for your money.
Tested at £5000
This Award-winning E6 essentially has the same screen as LG's 2016 flagship OLED65G6V, but with a slightly smaller soundbase. It's £1000 cheaper, too.
What about OLED phones?
OLED displays have been used in phones for a good few years, with AMOLED the most common type of OLED screen for portable devices. While LG dominates larger OLED panel production, Samsung has something of a monopoly when it comes to smaller screen sizes.
Recent flagship phones including the LG V30, Samsung Galaxy S8 and OnePlus 5 have all used AMOLED screens, and they've now been joined by the new Apple iPhone X, after Apple reportedly ordered 70 million OLED screens from Samsung.
OLED screens on phones allow for the same picture performance benefits as seen on OLED TVs - brighter, more dynamic colours and deeper blacks - while also helping deliver lightweight, super-slim displays. OLED screens can also be curved or flexible, which is proving increasingly useful as smartphone designs evolve.