Periodic Reporting for period 5 - TWIST (Twisted Perovskites - Control of Spin and Chirality in Highly-luminescent Metal-halide Perovskites)
Periodo di rendicontazione: 2025-04-01 al 2025-12-31
The ERC project TWIST investigated whether electron‑spin control and crystal‑handedness (chirality) can be exploited in hybrid metal‑halide perovskites—materials already vital for high‑efficiency solar cells and LEDs. Modern technologies such as data storage and quantum communication benefit from spin manipulation and circularly polarised light, yet perovskites have been used only for charge transport and emission, leaving their magnetic and chiral capabilities untapped. TWIST asked whether tiny amounts of magnetic ions can be added without harming optoelectronic performance and whether the lattice can be engineered to emit bright circularly polarised light intrinsically. The work showed that magnetically‑doped perovskites exhibit strong opto‑spintronic interactions for all‑optical spin control and that newly discovered chiral hybrid perovskites are promising emitters for photonic and optoelectronic applications.
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.
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.
During TWIST’s lifetime the programme far outgrew its original roadmap, delivering a series of spin‑optics breakthroughs in chiral and magnetically‑doped hybrid perovskites.
The team showed that transition‑metal ions can be incorporated into both layered Ruddlesden‑Popper and three‑dimensional metal‑halide perovskites at loadings of tens of percent while retaining paramagnetism and good photoluminescence efficiencies. The project discovered systematic tuning of the Néel temperature in cobalt‑halide antiferromagnets via the organic spacer and halide with unusually strong exchange interactions. These synthetic routes have become reference procedures, opening a reliable platform for spin‑physics studies in a class of semiconductors that was previously inaccessible.
A hallmark of the project is the ultrafast holographic Faraday‑rotation microscope which captures spatio‑temporal spin‑pattern evolution with unprecedented speed and sensitivity, exposing subtle charge‑spin transport imbalances and providing a foundation for ultrafast spin‑dynamics investigations across many material systems.
Transition-metal doping was found to raise the luminescence yield of layered perovskites and, under strong magnetic fields, to generate intense circularly polarised emission by lifting spin degeneracy. Even without external fields, low‑level doping extends spin lifetimes through motional narrowing. Complementary compositional engineering of chiral perovskites amplified these lifetimes by orders of magnitude, pointing to materials where spin coherence persists on technologically relevant timescales.
Work on chiral perovskites produced several state‑of‑the‑art advances. By dissecting the excitonic origin of circularly polarised luminescence, the team identified crystal symmetries that maximise CPL, establishing a clear design rule for future emitters. Exciton funneling toward emissive sites further boosted CPL quantum yields, opening a realistic pathway toward efficient circularly polarised LEDs.
Collectively, these results place TWIST at the cutting edge of spin‑optical perovskite research, yielding high‑visibility publications, a patent‑application for a device concept, and experimental tools now shared with the wider community. The outcomes deepen fundamental understanding of spin and chirality in hybrid semiconductors and lay a solid foundation for future spin‑optoelectronic devices and circularly polarised light sources that could transform information processing, communication, and sensing technologies.
The team showed that transition‑metal ions can be incorporated into both layered Ruddlesden‑Popper and three‑dimensional metal‑halide perovskites at loadings of tens of percent while retaining paramagnetism and good photoluminescence efficiencies. The project discovered systematic tuning of the Néel temperature in cobalt‑halide antiferromagnets via the organic spacer and halide with unusually strong exchange interactions. These synthetic routes have become reference procedures, opening a reliable platform for spin‑physics studies in a class of semiconductors that was previously inaccessible.
A hallmark of the project is the ultrafast holographic Faraday‑rotation microscope which captures spatio‑temporal spin‑pattern evolution with unprecedented speed and sensitivity, exposing subtle charge‑spin transport imbalances and providing a foundation for ultrafast spin‑dynamics investigations across many material systems.
Transition-metal doping was found to raise the luminescence yield of layered perovskites and, under strong magnetic fields, to generate intense circularly polarised emission by lifting spin degeneracy. Even without external fields, low‑level doping extends spin lifetimes through motional narrowing. Complementary compositional engineering of chiral perovskites amplified these lifetimes by orders of magnitude, pointing to materials where spin coherence persists on technologically relevant timescales.
Work on chiral perovskites produced several state‑of‑the‑art advances. By dissecting the excitonic origin of circularly polarised luminescence, the team identified crystal symmetries that maximise CPL, establishing a clear design rule for future emitters. Exciton funneling toward emissive sites further boosted CPL quantum yields, opening a realistic pathway toward efficient circularly polarised LEDs.
Collectively, these results place TWIST at the cutting edge of spin‑optical perovskite research, yielding high‑visibility publications, a patent‑application for a device concept, and experimental tools now shared with the wider community. The outcomes deepen fundamental understanding of spin and chirality in hybrid semiconductors and lay a solid foundation for future spin‑optoelectronic devices and circularly polarised light sources that could transform information processing, communication, and sensing technologies.