Researchers Transfer Chirality to Enhance Optoelectronic Material Properties

Researchers at Buffalo have achieved a significant result in materials science: successfully transferring chirality, the property of being left- or right-handed, to a non-chiral molecule, creating a novel material with enhanced optoelectronic potential. In a study published in Nature Communications following an early-access release, the team chemically combined a chiral perovskite semiconductor with an organic compound to overcome a key limitation of these materials, their inability to efficiently absorb visible light. The resulting system can absorb visible light and distinguish between left- and right-handed light waves, potentially advancing areas like optical communications and sensing. “We were able to transfer the properties of chirality to a non-chiral molecule,” says Wanyi Nie, associate professor in the UB Department of Physics and the study’s corresponding author, explaining that the material “retains the handedness while adding the ability to respond to visible light.”

Chiral Perovskites Enhanced with F4TCNQ Dopant for Visible Light Absorption

This achievement, detailed in a recent Nature Communications publication following an early-access release, addresses the inefficiency of many chiral semiconductors in capturing visible light, a crucial factor for practical applications. Traditionally, these materials primarily absorb ultraviolet light due to their large bandgap, hindering their use in technologies reliant on the visible spectrum. The University at Buffalo-led team, supported by the National Science Foundation, tackled this challenge by chemically combining a perovskite-based chiral semiconductor with F4TCNQ, an organic molecule known for its ability to readily accept electrons. This dopant molecule effectively lowered the energy threshold for light absorption, enabling the composite material to respond to visible light while retaining the chiral properties of the perovskite. The resulting charge transfer state, where electrons move from the chiral host to the dopant, is key to this enhanced functionality.

Co-author Dave (Hsinhan) Tsai, assistant professor in the UB Department of Chemical and Biological Engineering, illustrates the interaction using an analogy to a basketball play. “The chiral molecule is the guard and the dopant molecule is the forward. Guards read the play and then pass the ball to the forward,” he says. This “assist” allows the material to differentiate between left- and right-circularly polarized light, potentially improving applications like advanced polarized light sensors, optical communications, and photocatalysis. Currently, the team is focused on elucidating the precise mechanisms governing the transfer of chiral properties from the semiconductor to the dopant molecule; Nie notes, “We see that the ability to tell left- from right-handed light is being passed from one material to another, but we don’t yet fully understand how electrons carry that information across, and what governs this process.”

Electron Transfer Mechanism Transfers Chirality Between Host and Dopant Molecules

Researchers are increasingly focused on harnessing chirality, the property of being non-superimposable on its mirror image, in semiconductor materials for advanced optoelectronic applications, but a longstanding limitation has hindered progress. Many chiral semiconductors efficiently absorb only ultraviolet light, restricting their functionality. The key to this innovation lies in an electron transfer mechanism between the perovskite host and the dopant molecule, F4TCNQ, which readily accepts electrons. This transfer is not merely additive; the resulting material maintains the handedness inherent to chiral semiconductors, adding a crucial new capability.