Diamond Annual Review 2023/24

45 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 3 / 2 4 Caging chromophores offers a bright future for organic optoelectronics Organic electronic devices, based on organic materials instead of traditional inorganic semiconductors, are already finding their way into consumer devices. Your smartphone display, for example, may take advantage of organic light-emitting diodes (OLEDs). Organic electronics is a rapidly growing field of research developing next-generation electronic devices with potential applications in everything from healthcare to renewable energy. The unique properties of organic materials, such as their flexibility, low cost, and environmental sustainability, make them an attractive alternative to traditional electronic materials. However, although printable optoelectronics show great promise in the lab, this is frequently not transferred to real-world situations. The problem lies in the molecules’ tendency to stick together, an aggregation that adversely affects their electronic properties.​ Researchers report the development of a self-assembling supramolecular pseudo-cube formed from six perylene diimides (PDIs). This rigid cage assembly prevents these chromophores fromaggregating and therefore retains their electronic properties. It also creates an excited multimer that acts as an excited-state reservoir. They used X-ray Diffraction at I19 beamline to prove that they have created the desired structure. The cube was as they designed it. Their results demonstrate that self-assembly is a powerful tool for retaining and controlling the electronic properties of organic semiconductors, bringing molecular electronics deviceswithin reach.​Exciting as these discoveries are, the teamhas a long list of future research projects, includingmaking themolecules chiral to see if they can produce circular-polarised light and introducing guest molecules into the supramolecular cages. Heckelmann, I. et al. DOI: 10.1002/anie.202216729​ Figure: Synthesis and structure of the supramolecular pseudo-cube. a, Self-assembly of PDI ligand L into pseudo-cube C with only one of six ligands depicted for clarity. b, Structure of C as derived from synchrotron-based single-crystal X-ray diffraction. Counterions and co-crystallised solvent molecules are omitted for clarity. c, Relative orientation of possible PDI transition dipole moment couplings in the cubic cage. Pushing boundaries in piezoceramics: The impact of strontium acceptor dopants Conventional PZT piezoceramics – used in everything from spark generators and parking sensors to medical ultrasonics – can’t function at high temperatures, limiting their industrial applications. They’re also lead- based materials, which face legal restrictions due to their toxicity to people and the environment. In light of these issues, there is considerable interest in developing lead-free, high temperature piezoelectric materials. BiFeO3-BaTiO3 (BF-BT) ceramics are promising candidates, and researchers at the University of Manchester have been seeking to understand the mechanisms of how we can process and modify the composition of these materials to improve their properties. To do so, they have been working with a spin-out company from the University of Leeds. They investigated the unusual technique of adding strontium as an acceptor dopant. Although the strontium disrupted the microstructure – as expected – the team found that, in small amounts, it still improved the ferroelectric and piezoelectric properties. They used in situ synchrotron X-ray diffraction at the I15 beamline and digital image correlation (DIC) macroscopic strain measurements to measure the electric field-induced strain. This work demonstrates that acceptor dopants can be used to tune piezoelectric properties. The lightly Sr-doped 0.7BiFeO3-0.3BaTiO3 ceramics exhibited a high Curie temperature (around 500 °C ) and enhanced ferroelectric and piezoelectric properties, making them potential candidates for high temperature lead-free piezoelectric materials in the future. Yang,Z. et al . DOI:10.1016/j.jmat.2023.04.007 Figure: (a) Macroscopic strain-electric field relationships determined from the analysis of XRD peak profiles for the Sr-doped BF-BT ceramics. (b) Comparison of the strain-field results obtained from analysis of XRD data and DIC measurements for both 0.3Sr and 1.0Sr BF-BT ceramics.