Scientists discover how to control annihilation of photoexcitations

A recent study published in the journal Nature Chemistry challenges the conventional belief that photoexcitations, which occur when photons interact with a material, always annihilate each other upon proximity. Researchers from Northwestern University and Purdue University have found evidence that the annihilation of photoexcitations depends on the quantum phase relationships between them. Quantum interference, typically considered fragile, was shown to play a crucial role in determining the behavior of photoexcitations.

The team manipulated the crystallization of perylene diimide molecules, an industrial dye, by introducing different chemical side-groups. This led to the formation of crystals with distinct motifs and resulted in photoexcitations with contrasting quantum phase relationships. Consequently, the rate of annihilation varied significantly by orders of magnitude.

To confirm their findings, the researchers conducted quantum chemical calculations to predict the annihilation rates and validated these estimates through spectroscopic measurements. They employed techniques such as time-resolved microscopy-spectroscopy to separate the contributions of excitation mobility and the annihilation process itself.

The implications of this research are promising, as it opens up new possibilities for developing more efficient devices like solar cells. By achieving precise control over the quantum phases of photoexcitations through tailored crystal packing motifs, it may be feasible to enhance the density and mobility of these excitations. This breakthrough has implications in various fields, including optoelectronics and quantum information science.

According to Roel Tempelaar, an assistant professor of chemistry at Northwestern University, this research represents a significant advancement in molecular material design, utilizing quantum interference as a fundamental component. The ability to harness quantum interference may pave the way for the development of advanced molecular materials with diverse applications.

Source: Northwestern University

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