Research led by scientists 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), 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.” Most traditional optoelectronic devices in use today exploit control of charge and light but not the spin of the electron.
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.
The details are spelled out in a newly published paper, “Remote Chirality Transfer in Low-Dimensional Hybrid Metal Halide Semiconductors,” which appears in the journal Nature Chemistry. The key was in introducing a chiral molecule with a different headgroup into the perovskite. The chiral molecule intentionally does not fit into the perovskite lattice but “twists” the structure from the surface. The chiral molecule transfers its properties several unit cells or layers deep into the perovskite structure. This twist can be controlled by employing left- or right-handed chiral molecules into the grain boundaries and surfaces of a perovskite film, which control the spin properties accordingly. Such twisted structures enable unique functionalities for energy applications where spin-control adds additional potential by acting as electronic spin filters.
Md Azimul Haque, the first author of the paper, said introducing chirality to the low-dimensional perovskite semiconductors generally includes a chiral molecule being present in the perovskite lattice, which needs extensive analysis every time one changes the composition of the chiral molecule. The ability of a proximal chiral molecule to transfer its properties without changing the perovskite composition makes the process simple, faster, and less limiting on the composition, he said.
“We can create materials with known properties now with added chirality very easily compared to traditional methods,” said Haque, a postdoctoral researcher. “The next step is to experiment with the materials and incorporate them into new applications.”
Funding for the research comes from the EFRC program of the Office of Science within the Department of Energy. The work relied on a broad range of expertise drawn from CHOISE, including NREL, University of Utah, University of Colorado Boulder, University of Wisconsin–Madison, and Duke University.
Hybrid perovskites refer to a crystalline structure, containing both inorganic and organic components. In other semiconductors, such as those made from silicon, the material is purely inorganic and rigid. Hybrid perovskites are soft and more flexible, “so a twisting molecule on the surface, will extend the effect deeper into this semiconductor than it can in most rigid, inorganic semiconductors,” said Joey Luther, an NREL senior research fellow and corresponding author.
His coauthors from NREL are Steven Harvey, Roman Brunecky, Jiselle Ye, Bennett Addison, Yifan Dong, Matthew Hautzinger, Kai Zhu, Jeffrey Blackburn, Joseph Berry, and Matt Beard. Other coauthors from CHOISE include Andrew Grieder, Yuan Ping, Junxiang Zhang, Seth R. Marder, Heshan Hewa Walpitage, Zeev Valy Vardeny, Yi Xie, and David B. Mitzi.
“This is a new way to induce chirality in halide perovskites,” Luther said, “and it could lead to technologies that we can't really envision but might be somewhere along the lines of polarized cameras, 3D displays, spin information transfer, optical computation, or better optical communication—things of that nature.”
