Organic radicals—molecules with an unpaired electron—could replace the dark, energy-wasting states that plague today’s organic semiconductors. Current organic light-emitting diodes (OLEDs) and solar cells lose efficiency because some of their excited electrons fall into low-energy “triplet” states that cannot emit light or contribute to current. The researchers propose building a new class of open-shell organic semiconductors that, because they already contain an unpaired electron, have no such dark states. This means nearly every excited electron can be used—for light emission in displays, or for charge generation in photovoltaics. The team will chemically modify a known radical (TTM) to create three types of materials: narrow-band emitters for sharper, more efficient screens; radical-based polymers that absorb sunlight strongly for solar cells; and high-spin systems that can be controlled with light for quantum technologies. If successful, the work could push display and solar-cell efficiencies beyond current limits and open a route to optically addressable spin states for quantum computing. This is fundamental science—no device is ready for market—but it directly tackles a core physical bottleneck in organic electronics.
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The development of new materials and devices that are relevant towards achieving net-zero either by energy generation OR by reducing power consumption is of critical importance to avoid the worst effects of climate change. Closed shell organic semiconductors have been phenomenally successful in energy related device applications. Organic Light Emitting Diodes (OLEDs) have become ubiquitous technology and organic photovoltaic devices (OPV) have efficiencies approaching those of conventional inorganic technologies. In order to move beyond the state-of-the-art it is necessary to overcome the fundamental issue associated with dark, low energy triplet states in these materials. We propose to create a new family of organic semiconductors and devices based on open-shell materials. The materials have the unique combination of high luminescence efficiency and absence of lower energy dark states meaning that the major loss processes in current generation optoelectronic devices can be overcome. Additionally, the presence of unpaired electrons means that these materials can also be used to optically generate high-spin states for use in quantum applications. Following on from our initial discovery that organic radicals based on (tris[2,4,6-trichlorophenyl] methyl) TTM can be made emissive through correct chemical functionalization. We propose a series of chemical systems which will achieve improved and unique optical properties. We will then use these new materials to understand and demonstrate their performance in a series of (spin)optical device applications. Specifically we will aim to design i) highly emissive, stable organic radicals with narrow FWHM for use in display technology. ii) strongly absorbing radical based polymers for use in organic photovoltaics and iii) high-spin radical systems which can be optically manipulated. Thus we propose a true paradigm shift in organic optoelectronic design and function by moving from closed-shell to open-shell systems. In doing so we believe that we open the door to a new chapter of spin and optically active materials which retain or improve upon all the benefits of traditional organic semiconductors whilst eliminating their biggest problems.
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