Developing Long-lived Room-temperature Phosphorescence Under Optical And Electrical Excitation

Long persistent phosphors are widely commercialized as glow-in-the-dark paints for watch indicators and emergency signs. Although present glow-in-the-dark materials are made using inorganic materials, some organic molecules are also known to show long-lived emission called phosphorescence. Organic long-lived phosphorescent materials have advantages in areas such as solubility, color tunability, processability, and biocompatibility.

Phosphorescence, which is a spin-forbidden transition from the triplet excited state to the single ground state, is often quenched by the competing nonradiative deactivation process at room temperature. To observe long-lived phosphorescence from organic molecules at room temperature, the nonradiative deactivation needs to be minimized. The origin of this nonradiative deactivation can be divided into components from the guest emitters and host matrices. To suppress the nonradiative deactivation caused by the host matrices, host-guest systems using hosts that are polymers, hydroxyl compounds, and crystalline molecules have been reported. However, all of these systems are electrical insulators because they have nonaromatic backbones, so they are not suitable for use in semiconducting devices.

Here, Prof. Kabe, Prof. Adachi, and co-workers from Kyushu University report long-lived phosphorescence at room temperature through suppression of the nonradiative deactivation in conventional organic semiconducting host-guest systems, which are often used as the emitting layer of organic light-emitting diodes (OLEDs).

The researchers found that long-lived triplet excitons of the guest emitters can be transferred to host molecules even when the triplet energy level of the host is higher than that of the guest emitters. Because this reverse energy transfer is a thermally assisted process, nonradiative deactivation by the host matrix is significant at room temperature in the conventional host-guest system. To confine the long-lived triplet excitons to the emitting molecules, a very large triplet energy gap between the guest emitters and the host molecules of over 0.5 eV is required. By confining the long-lived triplet excitons in the semiconducting host-guest system, they demonstrated long-lived room temperature phosphorescence from OLEDs.

Because the triplet exciton dynamics is important for many optoelectronic devices such as OLEDs, organic solar cells, photon-upconversion systems, and non-linear optics, obtaining long-lived triplet excitons in semiconducting host-guest systems will help to advance the understanding of these devices.

This study, Confinement of long-lived triplet excitons in organic semiconducting host-guest systems was recently published in the journal Advanced Functional Materials and selected as a back cover.

About The Author

Ryota Kabe
Ryota Kabe is an associate professor at Kyushu University in the Department of Chemistry and Biochemistry. Their areas of expertise are X-ray diffraction, fluorescence, crystallization, and semiconductor technology. Their research focuses on organic long persistence luminescence.

Speak Your Mind!

READ THIS NEXT

How Studying The Resting Brain Might Help Us Understand Why Night Owls Are At Increased Risk Of Developing Depression

It is estimated that 322 million people worldwide suffer from major depression every year. Depression is a serious mental health condition that can have debilitating effects on the individual and is a leading cause of disability. Understanding how this condition develops and identifying risk factors are key to developing strategies that work to prevent depression. […]

Developing Carbon-limiting Disposal Scenarios For Urban Pruning Waste

The removal of branches, fruits, inflorescences or foliage from urban afforestation promotes the longevity of trees, and the residues generated correspond to a significant portion of municipal solid waste. These residues are usually disposed of in landfills or dumps and, in some cases, incinerated. Urban tree and woody yard residues (urban pruning waste) represent a […]

The Psychology Of Vegetarianism

It seems like more and more people are going vegetarian nowadays, giving up meat and jumping aboard the bandwagon of plant-based dieting. Shifts in consumer preferences are accompanying the introduction of new plant-based products, from lab-grown meat alternatives to a plethora of dairy-free milk, cheeses, and ice creams. Vegetarianism has long garnered interest from the […]

Breaking The Acoustic Resolution Limit With A Metamaterial Magnifying Lens

The acoustic microscope is a critical component for a variety of applications including quality control, medical imaging, biomedical sensors, and focused ultrasound surgery, owing to its ability to distinguish objects separated by a small distance. The notion of an acoustic microscope can be traced back to 1936 when Sokolov proposed a device to provide magnified […]

Things That Start With A

According to the World of Science dictionary, over 100 science-related terms start with the letter A, from abiotic to atomic to azygos. This article catalogs a number of scientific words and concepts that begin with the letter A; concepts that help build a general backbone of scientific knowledge. With that in mind, grad you dictionaries as […]

On Dynamics Of Sine-gordon Soliton Under External Forcing

Solitons are pulsed like waves that propagate and collide with each other without losing their speed, shape or amplitude. This was first observed by John Scott Russel in a water canal near Edinburgh in 1834. Since then they have been found in several other fields like optical fibers, superconductor devices and galaxies from scales ranging […]

Welcome To Your Autonomous Life: Self Driving Cars Are A New Reality

Autonomous vehicles have become a hot topic among professionals in both automotive and technology fields. Recent headlines have consumers dreaming about their own personal robot chauffeur; but how close are we really? We will undoubtedly be able to sit behind the wheel (if the steering wheel will be there at all), enter a destination into […]