Grades 6–8 · Computing
How can an OLED screen make light at each pixel?
An OLED display contains tiny light-emitting regions controlled by electrical circuits. OLED means organic light-emitting diode. Here, organic refers to carbon-containing materials in thin layers, not to food or living organisms.
In the diagramLight is emitted within the OLED stackelectrodeemitting layer−+lightelectrons + holes → light-producing excitationSubpixels are controlled to form an imageLayer thicknesses are enlarged; color designs vary by display.
When a suitable voltage is applied, one electrode supplies electrons and the other creates electron vacancies called holes. Charges move through the layers. When an electron and a hole combine, energy can be released as light from the emitting material.
The screen controls different regions to form an image. Red, green and blue light contributions combine in our vision to produce many colors. Different products generate these colors in different ways, including direct emission and color-conversion layers.
An LCD usually controls light from a separate backlight. An OLED region produces its own light, so a region intended to be black can be switched off. That difference explains the strong dark contrast, although real screens still have reflections, control limits and aging materials.
About this explanation
Starting knowledge: Know that pixels form images and electrical charges can move in materials.
Sources
- U.S. Department of Energy — OLED Basics