Novel semiconductor generates circularly polarised light

Researchers under the leadership of Professor Dr Felix Deschler at Heidelberg University’s Institute for Physical Chemistry have developed a semiconductor that can generate light while simultaneously giving that light a certain spin. According to the researchers, the so-called chiral perovskite material has great technological potential that could be suitable for optoelectronics, telecommunications and information processing.

Materials science researchers have previously tried to generate bright, circularly polarised light. It is considered difficult to achieve a distinct chirality — which describes the rotation of light in a specific direction — as well as high photoluminescence quantum efficiency (PLQE). The PLQE value expresses the ability of a material to emit light. Inorganic semiconductors are able to emit high brightness but usually exhibit low light polarisation. In contrast, organic molecular semiconductors have high polarisation, but their brightness can be limited by losses due to dark conditions.

“Until now, a material that truly combines the high luminescence quantum efficiency of inorganic semiconductors and the strong chirality of organic molecular systems has been lacking,” Deschler said.

To obtain the desired brightness and high polarisation, the researchers developed a hybrid metal-halide perovskite semiconductor with a layered structure. The researchers integrated a customised chiral organic molecule into the perovskite structure as a hybrid component. Using a small aromatic molecule with a precisely placed halogen atom in the aromatic ring gave rise to novel chiral perovskites with the structural designation R/S-3BrMBA2PbI4. Doctoral candidate Shangpu Liu said the ability to dramatically alter the structure while training good material performance underscores the ability of perovskite materials to tolerate distortion in the crystal structure.

Due to their distorted crystal structures, chiral 3BrMBA2PbI4 perovskites exhibit a better degree of circularly polarised luminescence than other materials, even at room temperature. Using laser spectroscopy measurements, the researchers unravelled the processes behind the generation of this special light. The researchers were also able to show that the novel materials are promising for applications that require circularly polarised light. They implemented the materials in light detectors that can record and differentiate the chirality of the incident light. The researchers also developed light-emitting diodes (LEDs) from which light can be generated from electricity.

The research findings were published in the journal Science Advances.

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