1. What is LTPO

To put it simply, LTPO is a relatively new technology for producing display panels that allows them to use battery power more efficiently due to a dynamic refresh rate. In fact, it is a modification of an OLED display that uses low-temperature polycrystalline oxide (LTPO) instead of polycrystalline silicon (LTPS).

Apple Watch with dynamic refresh rate.

Displays like these were first tested by Apple in 2018, when the company was banging its head against the wall trying to solve the Apple Watch's constantly draining battery. Since then, the benefits of LTPO have attracted interest from other manufacturers of smartphones and other compact devices, where the screen is usually the biggest drain on battery power.

Popular smart watches with OLED display

2. Refresh rate and battery saving

Energy saving is one of the key tasks for mobile devices, because the duration of the gadget's operation without recharging directly depends on it. And it is the display that is one of the main energy consumers. The use of lithium-ion batteries of increased capacity helped to partially solve the problem of constant recharging, allowing the use of an average smartphone for several days. However, with the advent of displays with an increased refresh rate of 90 Hz, 120 Hz, the problem partially returned.

Most flagship smartphones of recent years support 120Hz refresh rate.

Recall that the display refresh rate indicates how many times the screen is updated per second and is measured in hertz (Hz). For a long time, the standard for mobile screens was 60 Hz. With this refresh rate, the screen is redrawn 60 times per second, which was optimal for most tasks that did not require highly smooth animation.

With the rise of fast-paced video and gaming (such as sports and action games), manufacturers have begun offering displays with refresh rates of 90Hz, 120Hz, and higher. Higher refresh rates make animations smoother and more responsive, but they also require more processing power and increase the display's power consumption, which in turn reduces the device's battery life.

This is where LTPO technology comes to the rescue, allowing the refresh rate to be changed adaptively depending on the content on the screen, reducing it when a high frequency is not needed.

Popular smartphones with LTPO display

3. Operating principles of the LTPO screen

To understand how LTPO works, it’s worth going back a few years to when OLED screens began appearing on the mobile, home, and computer market. A typical smartphone OLED panel consists of several layers: an emitter layer with organic light-emitting diodes that emit light, conductive layers that transmit electrical power, and protective layers to protect against external influences. Unlike other types of screens, each pixel in an OLED is controlled independently, allowing color and brightness to be changed at a macro level, and when “unnecessary” pixels are turned off, black looks truly black, not dark gray.

Basic diagram of an OLED screen.

Most OLED displays use low-temperature polycrystalline silicon (LTPS) for the transistors that are responsible for individual pixel operation. In general, LTPS provides high switching speeds and extremely precise pixel control, providing an unprecedentedly clear, bright and saturated picture. The downside is energy consumption. According to various estimates, an OLED screen can consume 20 - 50% more energy compared to IPS screens (depending on the brightness settings, refresh rate and content on the screen).

This is where LTPO (Low-Temperature Polycrystalline Oxide) comes in. It is essentially a modification of OLED that uses polycrystalline oxide instead of silicon. The main difference from LTPS is that LTPO allows the display to dynamically change the refresh rate depending on the content. This means that the refresh rate can drop to 1 Hz for static images, which significantly saves energy, and increase to 120 Hz for dynamic content, ensuring smooth images. This approach improves energy efficiency and extends the battery life of the device on a single charge, while maintaining all the benefits of OLED, including deep blacks and high contrast.

4. Which is better - LTPO or OLED?

At this point, some users may wonder what is better – OLED or LTPO? And as you may have guessed from the previous point, this is not quite the right way to put the question. LTPO is not a separate type of display, but rather a subtype of OLED, which is often called just that: LTPO OLED. The main difference between the two technologies is in the thin-film semiconductor transistors that control the individual operation of the pixels. And in terms of brightness, contrast, color rendering and black depth, they are virtually identical. It is also worth noting that Super AMOLED from Samsung is a slightly modified version of the OLED display, which can also support an adaptive refresh rate.

And now we come to the point. In recent years, smart watches and then smartphones have been equipped with screens with a high refresh rate. This indicator is measured in hertz and determines how many times per second the image on the display is updated. Previously, the standard was 60 Hz, now 90 Hz and 120 Hz screens are in fashion, on which the image in dynamics looks smoother and more pleasant. However, constant use of high refresh rates can greatly drain the battery. This is where LTPO comes to the rescue.

Low-temperature polycrystalline oxide allows screens to dynamically change the refresh rate from 1 to 120 Hz depending on the content on the screen. This is achieved due to the fact that LTPO manages the refresh rate adaptively, adjusting to the power tasks and the type of content displayed. Moreover, the screen does not have to follow generally accepted values like 60 or 90 Hz, if necessary, it switches to 15, 24, 99, etc. Hz.

OPPO Watch 3 Pro is one of the first Android smartwatches to support dynamic refresh rate.

Here's what it looks like in practice:

  • Static images and text. Since high refresh rates are not needed to display static content (books, text, interface), an LTPO display can reduce the refresh rate to a few hertz, minimizing energy consumption.
  • Watching movies. When watching videos, especially tech with a frame rate of 24 FPS (which is the standard for most movies), the screen can automatically switch to a refresh rate close to 24 Hz. This ensures synchronization with the frame rate of the video, which makes playback smoother and prevents possible screen tearing or artifacts.
  • Sports broadcasts: To capture fast movements and details during sports broadcasts, frame rates of 50 or 60 FPS are commonly used.
  • Games. In games where the frame rate can reach 60 FPS and above, adaptive hertz increases the screen refresh rate to the appropriate level, for example, 90 Hz or 120 Hz. However, it does this only if the smartphone's hardware is capable of providing a frame rate of more than 60 Hz in the game, otherwise the battery will be wasted.

This approach allows LTPO displays to efficiently manage power consumption and maintain optimal display quality, adapting to specific tasks and usage conditions.

Popular smartphones with OLED display

5. Equipment that uses LTPO OLED screens

Screens with an adaptive refresh rate were first discussed in 2018 after the presentation of the Apple Watch Series 4 smartwatch. Subsequently, this technology was used in the Apple Watch Series 5 and Series 6, as well as in smartphones from major Asian brands led by Samsung, Xiaomi, OnePlus and OPPO. Here are just a few examples of gadgets with such screens.

  • The Apple Watch 5 was one of the first wearable devices to feature LTPO displays, which significantly improved energy efficiency and extended battery life, especially when using the built-in sensors and wireless communication modules.
  • The Apple iPhone 13 Pro Max was the first Apple smartphone to use an LTPO OLED display with an adaptive refresh rate.
  • The Google Pixel 7 Pro was one of the first non-Apple flagships to use LTPO OLED technology. In addition to powerful hardware and a top-end camera, the smartphone stood out for its 6.9-inch display with a resolution of 3120x1440 pixels.
  • Xiaomi 12 Pro is the company's first smartphone with LTPO. Its 6.73-inch display supports a refresh rate of up to 120Hz, providing a smoother image and an improved user experience.
  • The Samsung Galaxy S22 Ultra also uses displays with LTPO 2.0 support, which allows the frequency to be reduced to 1 Hz, which is extremely convenient for saving energy when using the Always On function. At the same time, the official name of the screen sounds like “Dynamic AMOLED 2X” to emphasize the unique features of its displays.
  • Similar designations are used by other manufacturers like Realme, for example the display in the recent Realme GT 2 Pro is designated as AMOLED LTPO2.

6. Conclusion

The first iPad models with LTPO OLED screens are rumored to be released in 2027.

In conclusion, LTPO is a promising technology that offers significant advantages in energy efficiency and dynamic display refresh rate. Although the technology is currently used primarily in premium devices due to its high cost, its potential for wider use is obvious. If it continues to evolve and component prices fall, we will likely see this technology used in larger mobile devices such as tablets and ultrabooks in the future.