Analysis of Sony Micro OLED high-brightness technology

In order to expand the application fields of OLED micro displays, further realization of high brightness is most expected. Especially in the use of AR glasses, brightness in an external light environment is required, so it is urgent to increase the brightness of the display. Of course, in other application areas, high-brightness technology is also very useful and is highly expected as an important technology to help extend the service life of OLEDs and reduce power consumption.

In order to meet these needs, Sony Semiconductor Solutions (hereinafter referred to as SSS) has improved luminous efficiency by using its own technology of generating microlenses in pixels, which has increased luminous efficiency by 2.2 times compared with traditional technologies. In addition, the light passing through the microlens is more collimated, which helps reduce crosstalk between color filters and improves viewing angle characteristics.

Improve luminous efficiency by using microlens technology

As shown in the following figure, by configuring the microlens on the OCCF (On Chip Color Filter) in the pixel, the light exit efficiency from the front direction of the OLED light-emitting layer is increased to 2.2 times that of the traditional structure. In applications such as AR glasses that require high brightness, in principle, it is desirable to obtain more parallel outgoing light, so this luminescent characteristic is very beneficial for this. In addition, in applications that do not require high brightness, the technology will help reduce power consumption and extend service life.

Improved viewing angle characteristics by using microlens technology

Because the light emitted from the microlens will be more parallel, it has the characteristic of reaching a peak in the front direction. This characteristic is very advantageous for polarizing optical systems such as AR glasses and optical waveguide optical systems. At the same time, this feature also helps minimize interference between adjacent color filters, resulting in the improved viewing angle as shown in the following figure. The deviation of tristimulus values when observing from an oblique direction also becomes small, which has the effect of improving color cast.

In about 8 years, the maximum brightness increased to 10 times

In addition to improving brightness by introducing microlens technology, SSS has also continuously taken effective measures to improve luminous efficiency. As shown in the figure below, the maximum luminous brightness has been increased in stages. In the future, in order to expand the application of OLED micro display products, we will continue to work hard to further promote the improvement of brightness.

■ References

Youske Motoyama et al DISTINGUISHED PAPERS, BEST OF Display WEEK2019

High‐efficiency OLED microdisplay with microlens array