Active Chemistry Physics & Astronomy

Design and Characterization of Inverted Singlet and Triplet Excited States with Organic Radicals (DECOR)

In plain English

AI plain-English summary

A molecule’s first excited state usually traps energy as a dark, weakly emitting triplet state, wasting light and lowering device efficiency. This project flips that order, designing molecules where the first excited state is a bright singlet instead. The problem is fundamental: in most organic molecules, the lowest excited state is a triplet, which emits poorly and limits the performance of LEDs, solar cells, and photocatalysts. The researchers aim to break Hund’s rule—a basic quantum-mechanical principle—by creating “inverted” singlet–triplet molecules. They will couple these molecules to stable organic radicals, whose unpaired electrons allow magnetic measurements to confirm the inverted energy ordering. If successful, the work could enable more efficient upconversion, where low-energy light is converted to higher energy, effectively getting more usable work from less input. This would improve energy efficiency in displays, lighting, and solar cells, and could boost photocatalysis for making fine chemicals and pharmaceuticals with lower energy demand. The project is fundamental science—it explores a counterintuitive quantum effect in molecular design—but it directly targets UN Sustainable Development Goals for clean energy and responsible production. Past fundamental work on excited-state ordering has already transformed display and solar technologies.

View original technical description
The exchange of energy between p-conjugated molecules and light underpins current and future technologies for displays from light-emitting diodes, electricity generation in solar cells, bioimaging and photochemical production. These applications require molecules to transition between different excited energy states within a manifold of levels. The ‘normal’ ordering of molecules set the first excited states to have weak light absorption and emission properties, forming (triplet) states that are detrimental for these applications by lowering their efficiency. In this proposal we explore ‘inverted’ molecules – working against ‘normal’ expectations from quantum mechanics (Hund's rules) to solve this problem – where now the first excited states (singlet) exhibit strong light absorption and emission. By coupling these molecules to stable radicals with unpaired electron states we enable magnetic characterization of ‘normal’ vs ‘inverted’ order of levels. We will explore new opportunities in upconversion that converts lower energy states to higher energy: demonstrating the potential to get more energy and work done from less in future applications. This project will push the boundaries of spin and optical properties of advanced molecular materials for energy management with potential future applications in more efficient and sustainable energy generation and consumption (UN SDG 7: Affordable and Clean Energy; UN SDG 11: Sustainable Cities and Communities), as well as photocatalysis in production of fine chemicals and pharmaceuticals (UN SDG 12: Responsible Consumption and Production). The programme is enabled by two leading early-career researchers from the UK (Evans) and Japan (Aizawa) with complementary expertise in molecular materials design, characterization and exploitation.

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Researchers

Emrys Evans (Principal Investigator)

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Original classification

Research and Innovation

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