Perovskites

A University of North Carolina at Chapel Hill research team has demonstrated a novel way to encode quantum information directly within the light produced by two-dimensional perovskites - opening a potential path to simpler, more efficient quantum communication systems. The study explores how spin dynamics in two-dimensional organic–inorganic hybrid perovskite (2D-OIHP) quantum wells can generate polarization-encoded photons suitable for secure communication protocols.

Two-dimensional perovskites are well known for their performance in light-emitting and photovoltaic devices, but the UNC team, led by Professor Andrew Moran, has shown they can also act as microscopic light sources whose intrinsic exciton spin behavior defines the polarization of emitted photons. When ultrafast laser pulses excite the material, they generate pairs of bound charge carriers - excitons - whose spins determine the polarization of emitted light.

Researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) and the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center (EFRC), University of Wisconsin-Madison, University of Colorado Boulder, Duke University and University of Utah have discovered a new process to induce chirality in halide perovskite semiconductors, which could open the door to cutting-edge electronic applications.

The development is the latest in a series of advancements made by the team involving the introduction and control of chirality. Chirality refers to a structure that cannot be superimposed on its mirror image, such as a hand, and allows greater control of electrons by directing their spin. The researchers have been able to create a spin-polarized LED using chiral perovskite semiconductor in the absence of extremely low temperatures and a magnetic field, as was previously reported. The newest advance accelerates the materials development process for spin control.

In a recent sturdy, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northern Illinois University discovered that they could use light to detect the spin state in a class of materials called perovskites (specifically in this research methylammonium lead iodide, or MAPbI₃). 

To understand spin, consider electrons orbiting the atomic nucleus. When atoms are close together, they can share some of their outer electrons, which creates a bond between them. Each bond contains two electrons that are ​“paired,” meaning they share an orbital — the region where they move. Now, each of these paired electrons has one of two possible spin states: spin up or spin down. If one electron is spin up, the other is spin down. Since we can’t know exactly which electron has which spin without looking at them, we say they exist in a quantum superposition — a state where they are both spin up and spin down until observed.

Researchers from Cambridge University in the UK, Korea's DGIST and Harvard University in the U.S have shown that electron spins could become more efficient and easier to manage through a light-based approach using halide perovskite semiconductors. The team observed ultrafast spin-domain formation in polycrystalline halide perovskite thin films in response to irradiating the films with circularly polarized light at room temperature.

Photoinduced spin-charge interconversion in semiconductors, with spin-orbit coupling, could provide a route to spintronics that does not require external magnetic fields, which tend to be challenging to control. An electron can have two spin states, up or down, and these states can be used to store and process information. But manipulating spin states can be tricky, requiring the use of magnetic fields on perfectly ordered materials at extremely low temperatures to work.

A team of researchers at MIT, Complutense University of Madrid and the University of Pavia has designed a perovskite-based device that combines aspects of electronics and photonics, that could lead to new kinds of computer chips or quantum qubits.

The new work involved sandwiching tiny flakes of a perovskite material in between two precisely spaced reflective surfaces. By creating these perovskite sandwiches and stimulating them with laser beams, the researchers were able to directly control the momentum of certain “quasiparticles” within the system. Known as exciton-polariton pairs, these quasiparticles are hybrids of light and matter. Being able to control this property could ultimately make it possible to read and write data to devices based on this phenomenon.

Scientists from the University of Warsaw, Poland-based Military University of Technology, CNR Nanotec, the University of Southampton and the University of Iceland have designed a new photonic system with electrically tuned topological features, constructed of perovskites and liquid crystals. The new system can be used to create efficient light sources.

Perovskites are highly-studied materials that have the potential to revolutionize the solar energy fields, among others. These are durable and easy-to-produce materials, the special property of which is a high solar light absorption coefficient and they are therefore used to develop new, more efficient photovoltaic cells. In recent years, the emission properties of these materials, so far underestimated, have been used.

A team of researchers from the National Renewable Energy Laboratory (NREL) and the University of Utah has developed a new type of LEDs that utilizes spintronics without needing a magnetic field, magnetic materials or cryogenic temperatures.

“The companies that make LEDs or TV and computer displays don’t want to deal with magnetic fields and magnetic materials. It’s heavy and expensive to do it,” said Valy Vardeny, distinguished professor of physics and astronomy at the University of Utah. “Here, chiral molecules are self-assembled into standing arrays, like soldiers, that actively spin polarize the injected electrons, which subsequently lead to circularly polarized light emission. With no magnetic field, expensive ferromagnets and with no need for extremely low temperatures. Those are no-nos for the industry.”

Researchers from the NREL and the University of Utah have demonstrated how electron transport with a particular spin state through a two-dimensional hybrid organic-inorganic perovskite can be manipulated by introducing special organic molecules in the multilayer structure.

One way to control spin-polarized currents is through "chiral-induced" spin selectivity where the transport of electrons depends upon the transporting materials’ chirality—a structural property of a system where its mirror image is not superimposable on itself. The scientists have demonstrated how to integrate a chiral organic sublattice into an inorganic framework, creating a chiral system that can transport electrons with the desired spin control. In such systems, the chiral perovskite films act as a spin filter.

The Spintronics-Info team takes pleasure in recommending our new book - The Perovskite Handbook. This book gives a comprehensive introduction to perovskite materials, applications and industry. Perovskites offer a myriad of exciting properties and has great potential for several industry -including the spintronics one.

We believe that any spintronics professional would find that perovskite materials are an area of focus that should not be ignored. The promising perovskite industry is currently at a tipping point and on the verge of mass adoption and commercialization and the first display-related perovskites are already reaching the market.

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.