OLED Devices: Explaining Infinite Contrast Ratios
With an impressive range of unique selling points, organic light-emitting diode (OLED) devices have successfully enriched the display market to become one of the dominant technologies used in smart devices, cell phones, and – to a lesser extent – televisions.
Although conventional liquid crystal displays (LCDs) and premium, quantum dot-enhanced panels maintain a competitive edge – particularly with respect to peak brightness, color saturation, and manufacturing capacity – OLED devices offer unprecedented contrast ratios thus exceptional high dynamic range (HDR) performance.
In fact, OLEDs are often described as having technically infinite contrast ratios. This blog post looks at the unique architecture of OLED devices to explain the principle in more detail.
Basics of OLED Devices: Understanding Contrast Ratios
In display panel terminology, contrast ratios refer to the difference in luminance between the brightest white and the darkest black that a screen can produce at any one time. High peak brightness levels and vivid colors are now a staple of premium display technologies with high dynamic range (HDR) and wide color gamut (WCG) capabilities, yet this presents a risk of producing images that seem over-saturated with washed-out black areas. Maximising contrast yields more realistic pictures with brighter highlights and darker shadows.
This simple premise is complicated by the fact that manufacturers no longer report contrast ratios as a numeric key performance indicator (KPI). Even when contrast ratios were readily displayed, there has never been a standardized testing format, which means white-to-black levels could be tested with varying light outputs. The result would be an attractive yet inaccurate marketing product details.
Another complication to understanding contrast ratios is the fact that various external factors can impact the appearance of contrast on the screen, including ambient lighting, screen reflectivity and viewing angles.
Though it can be difficult to precisely quantify, video contrast is largely defined by two key parameters:
- Peak brightness: Expressed in candela per square meter (cd/m2), or nits.
- Black level: Determines the amount of light emitted from the darkest areas of an image.
OLED devices typically exhibit inferior peak brightness levels to LCDs as they are self-emissive, using no back- nor edge-lighting for illumination. This is used to their advantage when it comes to their black levels, however. Displays with LED lighting achieve black representation on screen by attempting to block as much of the incoming light as possible. In premium displays This is enhanced by localized dimming, but light from neighboring pixels can still bleed over, causing blacks to look grey. On an OLED device, the light output of each individual pixel can be switched off, which leads to true black representation on-screen.
OLED devices can obtain black levels of 0 nits, the result is a technically infinite difference between the darkest and brightest points on-screen.
Avantama: Materials Suppliers for OLED Devices
At Avantama, we specialize in the development of functional materials for display applications and OLED devices. If you would like to learn more, simply contact a member of the Avantama team today.