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 points of ultra-dark blacks (surpassing those previously seen on plasma TVs) and super-punchy contrast.
MORE: Best 4K OLED TV deals
But it hasn't been a smooth ride for OLED since then. First there was news 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. This left LG as the sole manufacturer of OLED screens.
Fast-forward to 2018 and we now have seven TV manufacturers with OLED sets in their TV line-up: LG, Panasonic, Sony, Philips, Toshiba, Bang & Olufsen and Loewe. The other six all source their panels from LG Display.
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 products 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 black levels from ultra-thin screens while, at the same time, making TVs 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 can't achieve true blacks as the backlight affects neighbouring pixels.
With an OLED panel, the organic pixels are self-emissive, which means they generate their own light - and so can become pitch-black when 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 in the OLED TVs we see today.
OLED also includes an additional white pixel alongside the usual red, green and blue sub-pixels, with the aim of delivering 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, as they don't require a separate backlight.
To give you an example of just how slim, LG showed off an OLED display just 0.97mm deep back in 2015, while you can actually buy the more recent "Wallpaper" TV (the £8000 OLED65W7), which measures just 2.57mm. It's really very flexible.
But of greater interest is 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 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 out at 800nits.
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 - 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 you still don't see OLED TVs smaller than 55in.
Prices have thankfully come down in the last few years, due in no small part to an increase in LG Display's yield for 4K OLED panels: the Philips 55POS9002 costs just £2000, while LG's OLED55B7V and OLED55C7V (originally priced at £3000 and £2500) are now available for around £1500. Bargain.
They're still pricey, though. 2017's Sony KD-55A1 cost £3500 at launch, although it's now available for around £2500. Larger 65in screens are naturally more expensive, too.
Another 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 conceivably be affected. We've never experienced any issues during our tests, mind you.
Thankfully, based on our most recent OLED TV experiences, the sets are definitely getting better, as well as 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 combined. LG introduced the first 4K OLED TV - the 55EG960V - in 2015, and since then it's become an incredibly impressive pairing.
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 and Award-winning 65A1, the Panasonic TX-55EZ952B (the HDR performance of which is its only weak spot), while all LG's 2017 OLED TVs come with Dolby Vision HDR support as standard. More recently still, the Ambilight-toting Philips 55POS9002 grabbed our attention with its stunning 4K HDR picture.
There are even more 4K HDR OLEDs in the pipeline: Panasonic revealed two new OLED ranges at CES 2018, LG unveiled its 2018 OLED TV series and Sony announced its new AF8 OLED range. We've also still yet to see Toshiba's first OLED, the 65X9863DB.
And if that wasn't enough, LG also showed off a mammoth 88in 8K OLED display at CES 2018 - not only the world's biggest OLED screen (current screens max out at 77in) but also the first time 8K resolution has been displayed on an OLED. A sign of things to come? We wouldn't be selling off your 4K TV just yet...
What about curved, flexible and rollable OLED TVs?
Thanks to the thinness of an OLED panel, manufacturers have been curving, bending and rolling them up to discover new ways of displaying and implementing display technology.
Samsung was the first to curve an OLED and, while there was a brief flirtation with curved TV screens in 2016, it's now fallen from fashion. In our opinion, a curved screen makes more sense on a phone - like the LG G Flex, G Flex 2 or Samsung Galaxy S8+ - than on a TV.
But it's LG Display who has been doing weird and wonderful things by developing flexible OLED screens, creating a 77in screen that's completely rollable, and there's the ultra-thin "Wallpaper" range, which sticks to your wall using magnets and wobbles a fair bit.
And at CES 2018, we laid eyes on a fully rollable 65in 4K HDR TV. It can change its aspect ratio according to what you're watching (either 16:9 or 21:9), roll down to just a bar of information showing weather and location, or simply disappear out of sight. Could this be the future of TV in the home? We're certainly intrigued...
While a lot of these displays are being developed for advertising signage, and others might seem like a novelty, we wouldn't be surprised to see some of the technology trickling 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 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.
However, Samsung - the main champion of this technology - has claimed its 2017 QLED screens deliver all the benefits of OLED (deep blacks) but with much brighter whites (beyond 1500nits of peak brightness) and 100% reproduction of the colour volume. Hisense has also jumped on the QLED bandwagon, having failed to impress rather with its own ULED (Ultra LED) take on the tech with the £2000 65XT910.
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 plumb 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 previously promised a 4K quantum dot TV, but is instead 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 results in more accurate colours and greater viewing angles - we're curious to see how this will improve on LG's own OLED performance, especially since it's now announced Nano Cell LCD TVs for 2018.
What are the best OLED TVs?
Tested at £2000 / compare latest prices
Adding Ambilight to OLED is a delight, but what wows us is the Philips's spectacular HDR performance - it's even better than Sony's A1. If you're after the best 4K HDR performance from an affordable OLED, this is our current favourite.
Tested at £4500 / compare latest prices
Sony's first 4K OLED range is stunning. Winner of a What Hi-Fi? Award 2017, this gorgeous 65in Sony is an absolute joy to behold. Pricey, but entirely worth it.
Tested at £3000 / compare latest prices
Have your heart set on an LG OLED and want the perks of Dolby Vision? Not only is this superb 4K OLED TV our 2017 Product of the Year for TVs, it's also had its price slashed in half - making it even more desirable than before.
Tested at £3500 / compare latest prices
Imagine the Sony 65A1, but more manageable in both screen-size and budget. The 55in A1 is just as good as LG's 2017 OLED TVs, and has a unique sound solution. It set a new benchmark for OLED screens.
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 (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.