Chemists at RIKEN have developed a new molecule that significantly enhances the performance of organic electronic devices while being more stable than previous alternatives.
This advancement could make it suitable for industrial manufacturing, according to a study published in Advanced Materials.
Traditional electronic devices are made from hard semiconductors like silicon.
However, organic semiconductor molecules are increasingly being used in devices such as OLED displays in televisions and cell phones.
These organic electronic devices offer the potential for thin, light, and flexible gadgets, which are difficult to achieve with inorganic materials.
“Organic electronic devices are strong candidates for thin, light, and flexible devices,” says Kazuo Takimiya, the lead researcher from the RIKEN Center for Emergent Matter Science.
Organic semiconductors need help from molecules known as dopants to improve their performance.
Dopants can enhance the flow of charge through the semiconductors. Some dopants, for example, have high-energy electrons that can be easily released into the semiconductor material.
However, existing electron-donating organic dopants tend to be unstable, making them difficult to design, synthesize, and handle.
Takimiya’s team had previously studied derivatives of a molecule called tetraphenyl dipyranylidene, which can readily donate electrons to organic semiconductor materials. By making further tweaks to this molecule, they improved its stability at high temperatures.
The most promising modification involved adding nitrogen-based amine groups, which push electrons into the molecule’s central region.
The resulting molecule, named DP7, was found to have electrons at a sufficiently high energy level. Experiments showed that DP7 is very stable and can be added to devices using vacuum deposition, a common process in semiconductor manufacturing.
The team tested DP7 in several organic electronic devices, including an organic field-effect transistor (OFET). This OFET consisted of a thin film of buckminsterfullerene (buckyballs) on top of a silicon-based substrate. The researchers added ultrathin patches of DP7 to connect the buckminsterfullerene layer to gold electrodes.
The interface between buckminsterfullerene and DP7 showed much lower electrical resistance than previous variants of the dopant. In fact, it had one of the lowest resistances of any electron-doped OFET reported to date, significantly enhancing the flow of electrons into the buckminsterfullerene layer.
Additionally, the device demonstrated remarkable stability, showing no degradation after being stored in an inert atmosphere for two weeks.
DP7 is also easy to produce from commercially available chemicals using just two chemical reactions. Takimiya is optimistic about its potential industrial applications. “For commercial devices, it could be used to improve the conductivity of the electron-transport layer in OLEDs, which are fabricated by vacuum processes,” he says.
The researchers are now on the lookout for other stable dopants with even greater electron-donating abilities. This development opens new possibilities for the design and manufacturing of organic electronic devices, paving the way for more efficient, stable, and flexible electronics in the future.
