Researchers have pioneered a new technology that could improve the efficiency and brightness of OLED displays used in television and smartphone screens.
The research team led by the University of Cambridge and the Eindhoven University of Technology created an organic semiconductor that forces electrons to move in a spiral pattern.
The semiconductor that the team developed emits circularly polarised light — meaning the light carries information about the ‘handedness’ of electrons.
The internal structure of most inorganic semiconductors, such as silicon, is symmetrical, which means that electrons move through them without any preferred direction.
However, in nature, the team said that molecules often have a chiral (left- or right-handed) structure.
By using molecular design tricks inspired by nature, the researchers created a chiral semiconductor by nudging stacks of semiconducting molecules to form ordered right-handed or left-handed spiral columns.
They say that one promising application for chiral semiconductors is in display technology. Current displays often waste a significant amount of energy due to the way screens filter light.
The chiral semiconductor developed by the researchers naturally emits light in a way that could reduce these losses, thereby making screens brighter and more energy-efficient.
In typical OLED displays, an external circular polarizer above the pixels absorbs roughly 50% of emitted light. The new technology, makes OLED pixels emit polarized light themselves, eliminating the need for an external polarizer, thereby reducing power consumption and boosting brightness, reported Flatspanel HD.
Polarizer-free OLEDs such as Samsung’s recently unveiled 5000-nit OLED use on-cell film (OCF) instead of an external polarizer, reportedly gaining about 33% brightness, according to Samsung.
The semiconductor by way of the new technology discovered by the research team is based on a material called triazatruxene (TAT) that reportedly self-assembles into a helical stack, allowing electrons to spiral along its structure.
“When excited by blue or ultraviolet light, self-assembled TAT emits bright green light with strong circular polarisation — an effect that has been difficult to achieve in semiconductors until now,” said co-first author Marco Preuss, from the Eindhoven University of Technology.
“The structure of TAT allows electrons to move efficiently while affecting how light is emitted.”
The researchers then modifying OLED fabrication techniques to successfully incorporate TAT into working circularly polarised OLEDs (CP-OLEDs). These devices, they claimed, showed record-breaking efficiency, brightness, and polarisation levels.
