Kyushu University scientists demonstrate that organic semiconductor laser diodes have been realized. This will start the era for laser applications in the fields of optical communications, healthcare, biosensing, and displays.
The field of light-emitting devices has always prodded scientists to search for carbon-based organic materials. This research has paved the way in organic laser diodes that use these materials in light emission instead of gallium arsenide and gallium nitride in inorganic semiconductors.
There are similarities between lasers and organic light-emitting diodes (OLEDs) as an application of electricity results to light emission of a thin layer of organic molecules. The high efficiency and vibrant colors of OLEDs have made these a popular option to smartphone displays.
The light produced by organic laser diodes is purer compared to that in OLEDs. However, the lasing process needs currents with magnitudes higher than those used in OLEDs. Devices that used in previous researches fail to function due to these extreme conditions before the process of lasing could be observed.
There were numerous false claims of generating electricity from the lasing of organic materials. Moreover, insufficient characterization has led to the incorrect identification of occasions as lasing.
Research findings of the scientists from the Center for Organic Photonics and Electronics Research (OPERA) at the said university have shown the possibility for the existence of organic semiconductor laser diodes. They published their results in the journal Applied Physics Express.
"I think that many people in the community were doubting whether we would actually one day see the realization of an organic laser diode," says Atula S. D. Sandanayaka, lead author on the paper, "but by slowing chipping away at the various performance limitations with improved materials and new device structures, we finally did it."
The crucial step in lasing involves population inversion where a large amount of electrical current is injected into the organic layers. The concern here is that organic materials are highly resistant to electricity.
Moreover, efficiency decreases of organic materials and devices due to different process loss that results in higher current needs.
"To overcome these obstacles, the research group led by Prof. Chihaya Adachi used a highly efficient organic light-emitting material (BSBCz) with a relatively low resistance to electricity and a low amount of losses--even when injected with large amounts of electricity. But having the right material alone was not enough," according to Nanowerk.
The team also created a grid-like structure on top of the electrodes to inject electricity into the organic thin films.
"By optimizing these grids, we could not only obtain the desired optical properties but also control the flow of electricity in the devices and minimize the amount of electricity required to observe lasing from the organic thin film," says Adachi.
