
2024 Isaac Newton Medal and Lecture
The Isaac Newton laureate for 2024 is Professor Sir Richard Friend for pioneering and enduring work on the fundamental electronic properties of molecular semiconductors and in their engineering development.
Professor Sir Richard Friend has made a transformative impact in the understanding and engineering of the electronic properties of molecular semiconductors.
In the 1980s, he and his group pioneered the fabrication of thin-film molecular semiconductor devices. They showed these could demonstrate clean operation of diode and transistor devices, even with much higher levels of structural disorder than tolerated in inorganic semiconductor devices. These devices provided a powerful test bed to explore the special characteristics of electronic excitations in molecular semiconductors. They were later developed to support field-effect transistor (FET) circuits, and with ambipolar semiconductors, operation of light-emitting FETs. Flexible transistor arrays on plastic substrates are currently developed for use as active-matrix backplanes for e-paper and liquid-crystal displays.
The discovery in 1990 that semiconducting polymers could be used in light-emitting diodes (LEDs) triggered substantial research activity, both academic and industrial. Methods to control charge injection and to raise electroluminescence efficiencies brought good operational performance. Cambridge Display Technology, supported by a series of fundamental patents, was set up to develop advance polymer LED technology for displays. It is now part of the Sumitomo Chemical Company and supports a fully commercialised technology.
Molecular semiconductors require an interface between an electron donor and an electron acceptor to separate electron and hole from the electrostatically bound (excitonic) state formed by photon absorption. Friend and his group showed that blends of donor and acceptor materials, arranged to have a large interfacial area, could give close to unity yield for charge separation. They developed fundamental understanding of the processes necessary for long-range separation of electrons and holes, and more recently of the factors that control undesired electron-hole recombination to ‘dark’ spin triplet states.
Friend’s most recent research is on ‘radical’ molecular semiconductors designed to contain an unpaired electron spin. This has revealed schemes to achieve very high luminescence yields from excited states in the spin doublet manifold that avoid the problem of low energy spin triplet states in standard closed-shell systems. For extended molecular architectures, this has allowed demonstration of optical read and write of spin states.
About the Isaac Newton Medal and Lecture
The Isaac Newton Medal and Lecture recognises groundbreaking physicists. It is the most prestigious award of the IOP, one of the largest physical societies in the world. The Medal and Lecture were established in 2009 and notable awardees include former Nobel Prize winners.
The award includes a gold gilt medal, a certificate bearing short citation and sponsored prize and is awarded annually at a celebratory reception. IOP values long-term relationships with Isaac Newton laureates, drawing on their knowledge to shape IOP’s strategic impact work to ensure the health of the discipline as well as inviting contributions for IOP’s Physics World which has a global readership.