Organic spintronics

Researchers at Osaka University have designed "bifacial" ladder polymers - rigid, double-stranded polymer backbones with two deliberately different molecular faces - that show chirality-induced spin selectivity (CISS) exceeding ±90%, among the highest spin-polarization values reported for an organic chiral material. 

The team's key innovation is a chirality-assisted synthesis: a C₂-chiral bifacial monomer, built with two different substituents in a syn arrangement, is polymerized so the resulting ladder polymer keeps a uniform facial orientation along the entire chain. That regioselective, "one-handed" backbone is what earlier bifacial polymer designs struggled to control. Thin films of the resulting homochiral polymer self-assemble into one-handed supramolecular helices, with circular dichroism signals over 100 times stronger than non-ladder or monomeric references, and the chiral structure survives brief exposure to 300°C.

Researchers RIKEN in collaboration with several other Universities, developed an organic solid-state spin filtering device. The device is based on a thin layer of artificial molecular motors.

The researcher explain that the artificial molecular motors demonstrate four times chirality inversion by light irradiation and thermal treatments during the 360-degree molecular rotation. This means that the spin-polarization direction of electrons that pass through the molecular motors are switched by light irradiation or thermal treatments.

Researchers from the University of Utah developed two spintronics devices based on perovskite materials. The researchers use these new devices to demonstrate the high potential of perovksites for spintronics systems. This is a followup to the exciting results announced in 2017 by the same group that showed advantages of perovskites for spintronics.

The researchers use an organic-inorganic hybrid perovskite material that has a heavy lead atom that features strong spin-orbit coupling and a long injected spin lifetime.The first device is a spintronic LED which works with a magnetic electrode instead of an electron-hole electrode. The perovskite LED lights up with circularly polarized electroluminescence.

Xiaoshan Xu, assistant physics and astronomy professor at the University of Nebraska-Lincoln (UNL), was awarded with $750,000 from the US Department of Energy (DoE) to advance his spintronics research.

The main target of Prof. Xu's research is to investigate how organic spintronics works, and hopefully advance organic spintronics materials and devices.

The European Research Council (ERC) granted a six-year €9.7 million grant to professor Jairo Sinova from Johannes Gutenberg University Mainz (JGU) for its spintronics research. Professor Sinova will collaborate with researchers from the UK and the Czech Republic.

The project is titled "Spin-charge conversion and spin caloritronics at hybrid organic-inorganic interfaces". The researchers hopes that by combining principles of inorganic spintronics with organic materials (polymers) they will achieve better results than if they used purely inorganic systems. The advantages of using polymers include the flexibility of the material, control over the physical properties, and the fact that they are relatively easy to produce.

Researchers from the University of Utah (the same professor whose "Spin Effects in Organic Optoelectronic Devices" talk we just posted on) developed a new platinum-doped polymer that can be used to create light emitting devices, efficient OLEDs and OPVs and perhaps even Spintronics-based memory devices.

The basic idea is to take an organic polymer and insert (dope) platinum atoms at different intervals. Different intervals result in different light colors - including white. So the same molecule can emit different colored light at the same time and thus achieve white light. The researchers created two versions of the same polymer. The Pt-1, which emits violet and yellow light as it has a platinum atom in every unit or link. The Pt-3 has a platinum atom every third unit and it emits blue and orange light. We do not have more information regarding how these materials can be used as Spintronics devices.

Professor Z. Valy Vardeny from the University of Utah talks about several important developments in the field of organic spintronics and magnetic field effect in organic optoelectronic devices.

Vardeny talks about a spin-OLED that they developed in 2012 using using two FM injecting electrodes, where the electroluminescence depends on the mutual orientation of the electrode magnetization directions. This development has opened up research studies into organic spin-valves in the space-charge limited current regime.

Researchers from Tohoku University have shown that electron spins can be preserved for long distances using optimized organic compounds. This is because organic compounds are made mostly from carbon, in which the spin–orbit interaction is quite small. Using fullerene (C60) films the researchers made devices in which electrons traveled up to 110 nm at room temperature while preserving their spin.

The researchers used fullerence because there's no hydrogen in it (common in other organic materials) and this helps reduce the hyper fine interactions between electron and nuclear spins that can induce spin-flipping events. They built an organic spin valve in which two ferromagnetic electrons are placed in contact with an organic layer.

Researchers from the University of Arizona and the University of Kaiserslautern demonstrated how organic molecules interact with the magnetic electrode in so-called spintronic devices. Organic Spintronics is interesting because organic semiconductors have several advantages as they can be manufactured cheaply and can be processes at low temperatures.

Using ultra-fast, time-resolved measurements probing the interface between an organic semiconductor and a magnetic metal, the researchers showed that spin controls the time an electron stay trapped in the molecule. This shows that the organic molecule interacts with the magnetic electrode in a spin-dependent way. This is called a spin-filter effect.

Researchers from the University of Utah developed a new kind of Spintronics OLED device known as a spin-polarized OLED. This is a light emitting bipolar spin valve which uses a magnetic field to align the spin of the electrons and the electron-holes in the organic materials - causing it to support more current and be brighter.

The researchers hope that in the future it will be possible to control the light color using magnets. This technology also promises to turn OLEDs brighter. It's still about five years away from commercialization - mainly because it requires a very cold (-28F, -33C) temperature currently.