The project was organised into four linked research strands. The first strand studied introducing transition‑metal ions into both layered and three‑dimensional perovskite crystals at concentrations ranging from a few percent up to several tens of percent while the host material stays paramagnetic and retains high‑quality optical behaviour. These “magnetically doped” perovskites provide a robust platform for studying how spins interact with light, even though the original aim of achieving ferromagnetism proved unattainable. The second strand shifted focus from ferromagnetic order to other spin phenomena, including antiferromagnetic cobalt‑halide perovskites whose magnetic transition temperatures can be tuned by changing the organic spacer molecules. A newly built holographic Faraday‑rotation microscope, the first of its kind to image spin patterns over large areas in real time, revealed how spin textures evolve on ultrafast timescales and how charge and spin transport become subtly unbalanced.
The third strand examined the photophysical impact of magnetic doping. Incorporating manganese ions into layered perovskites not only increased their light‑emission efficiency but also, under strong magnetic fields, produced intense circularly polarised luminescence by lifting spin degeneracy. Even without external fields, optically induced alignment of the manganese spins generated a large Verdet constant, a measure of magnetic‑optical activity, while low‑level doping was found to lengthen spin lifetimes through a motional‑narrowing effect. Parallel work on chiral perovskites showed that careful compositional design can extend these lifetimes by orders of magnitude.
The most productive strand dealt with chiral perovskite photonics. By dissecting the excitonic origins of circularly polarised emission, the team identified crystal symmetries that maximise the effect, providing a clear design rule for future emitters. A newly discovered chiral hybrid perovskite exhibited circularly polarised light output brighter than previously reported materials. To overcome the instability of colloidal chiral nanostructures, a surface‑functionalisation strategy was introduced that transfers chirality to bulk nanocrystals, resulting in highly ordered domains that lase at remarkably low thresholds. An unexpected result revealed that the strongest chiroptical activity can arise from mixtures that are not fully enantiopure, expanding the palette of compositions available for optimisation. Finally, using exciton funneling toward emissive sites within bulk nanostructures, the researchers showed how to boost the quantum yield of circularly polarised light, paving the way toward efficient light‑emitting diodes that emit directly in a defined handedness – a concept already protected by a patent application.
The results of this project have been disseminated through a variety of channels. A focus was the interaction with the scientific community at conferences through invited and contributed talks. To present the work to a broader audience, workshops with the interested public showcased the research topic. Engagement with the wider public happened through press releases and social media, presenting our work in an accessible form to society.
In summary, TWIST has clarified how magnetic dopants and chiral crystal architectures influence spin dynamics and light emission in perovskites, establishing a solid foundation for future spin‑optoelectronic devices and circularly polarised light sources. The knowledge generated not only deepens our fundamental understanding of spin and chirality in these versatile materials but also brings us closer to practical technologies that could transform information processing, communication, and sensing in the years ahead.
