Photodriven spin selectivity in chiral organic molecules and devices

Project Information

PHOTOCODE

Grant agreement ID: 101104276

DOI

10.3030/101104276

Project terminated on 31 October 2025

EC signature date 8 May 2023

Start date 1 October 2023

End date 30 September 2027

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 265 099,20

Coordinated by

UNIVERSITA DEGLI STUDI DI FIRENZE
Italy

Periodic Reporting for period 2 - PHOTOCODE (Photodriven spin selectivity in chiral organic molecules and devices)

Reporting period: 2025-10-01 to 2027-09-30

Summary of the context and overall objectives of the project

Optical control of electron spin in organic molecules, thin films, and optoelectronic devices has the potential to revolutionize multiple technological sectors, including renewable energy, illumination and displays, information technology, sensing, healthcare, and quantum computing.

The overarching goal of PHOTOCODE is to exploit a recently discovered phenomenon — the chirality-induced spin selectivity (CISS) effect — to achieve unprecedented control of spin processes in organic molecules and devices. To this end, the project investigates how electron spins are influenced by molecular chirality, using electron donor–acceptor (D–A) dyads as model systems and focusing on the mechanism of photoinduced electron transfer.

PHOTOCODE is structured around three main objectives, designed to establish how the CISS effect can be understood and harnessed at the molecular level:

Outgoing phase
Obj. 1: Identify the key molecular parameters that govern photoinduced CISS in chiral D–A organic dyads (e.g. optimal donor/acceptor molecules, bridge architectures, functional groups).
Obj. 2: Provide direct experimental evidence of how CISS influences the photophysics of organic dyads relevant for optoelectronic applications, using time-resolved electron paramagnetic resonance (EPR) spectroscopy.
Return phase
Obj. 3: Integrate the most promising dyads into prototype opto/spintronic devices — specifically, spin-organic photovoltaics (SOPVs) — to demonstrate how spin-selective transport can enhance photoconversion efficiency.

In the long term, PHOTOCODE aims to establish chirality as a powerful tool to control the interplay between light and electron spins. This will drive advances in opto- and spintronics and has the potential to deliver broad impact for: (1) society, through new devices that improve quality of life for European citizens; (2) the economy, by stimulating innovation; (3) policy, by contributing to green photovoltaic technologies that support the EU target of net-zero greenhouse gas emissions by 2050; and (4) international leadership, by positioning Europe at the forefront of next-generation optoelectronic and spintronic technologies.
In addition, the ability to control spins via molecular chirality offers exciting opportunities in quantum information science, where light-driven spin control and initialization can be applied to molecular spin qubits. In this way, PHOTOCODE contributes to several Quantum Flagship priority areas (such as quantum computing and quantum sensing) and consolidates Europe’s leadership in the second quantum revolution, reinforcing its scientific excellence and global competitiveness in quantum research.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

As part of the outgoing phase in the Wasielewski group (Department of Chemistry, Northwestern University), I focused on the spin photophysical characterization of chiral donor–acceptor (D–A) dyads using optical techniques (WP1) and electron paramagnetic resonance (EPR) spectroscopy (WP2). My work addressed two families of chiral molecules originally proposed in the project: in the first, chirality is placed on the bridge (D–chiral bridge–A), while in the second chirality is on the donor (chiral D–bridge–A). The study of the first family was published early in the fellowship, but it revealed critical limitations that encouraged me to concentrate on the second family. These latter molecules displayed ideal absorption and electron-transfer properties for our investigations. They consist of a helicene-based donor (a helical molecule previously shown to produce strong CISS polarization in devices) covalently linked to a perylenediimide (PDI) acceptor, well known for its electron-accepting ability. Within the first few months, I completed the photophysical characterization of this dyad and achieved Milestone 1 (M1).

Building on this result, I extended the study to additional dyads with the same donor and acceptor units but varying molecular bridge lengths. By tuning the bridge length, we maintained high charge-transfer efficiency while slowing down recombination of the charge-transfer (CT) state. This optimization produced CT states with lifetimes longer than 200 ns, which are ideal for detection by time-resolved EPR spectroscopy. This effort led to the first observation of a radical pair by EPR in helicene-based dyads. Further EPR experiments carried out in liquid crystals allowed us to probe the orientation dependence of the radical-pair features and to study the spin polarization mechanism with higher precision. To isolate the role of chirality, I also investigated achiral analogues of the dyads, providing a direct comparison. These experiments resulted in the direct detection of CISS-mediated spin polarization in dyads where chirality is on the donor rather than on the bridge (Milestone 2, M2). The analysis revealed that stronger CISS polarization occurs when the electron travels through a chiral bridge than when chirality is located only on the donor. This provides fundamental guidelines for rationalizing the CISS mechanism and holds significant potential for the future design of molecules for spintronics and quantum information science.

In parallel, I broadened my research on light-induced spin polarization mechanisms to a new class of molecules based on metalloporphyrins covalently linked to free-base porphyrin chromophores. This additional line of research produced important results. First, the conceptual framework of this approach was published as a review/perspective article. Second, transient absorption/EPR studies on a vanadyl–free-base porphyrin dimer experimentally demonstrated the strength of this strategy for quantum information science. Specifically, I observed the generation of a long-lived spin-polarized quartet state at room temperature, which could serve as a molecular qudit. This discovery opens promising directions for using light to manipulate molecular qubits based on transition metals under practical conditions. In collaborative work, we also proposed a novel spin polarization mechanism capable of polarizing both electron and nuclear spins, with potential applications in areas such as NMR spectroscopy. I am now extending these spin photophysical studies to additional metalloporphyrin-based dimers and trimers. Although these activities were not originally part of the proposal, they have substantially broadened the scope and strengthened the impact of PHOTOCODE.

During the return phase at the Laboratory of Molecular Magnetism (University of Florence), I started exploring the technological applications of the studied chiral D–bridge–A dyads for organic photovoltaic devices and photodynamic therapy. Despite encouraging preliminary results, these activities were interrupted after one month to allow me to begin two individual grants (ERC and FIS) and establish my independent career as a group leader.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

During PHOTOCODE, I investigated new spin-photophysical pathways in different classes of molecules. While the results of my outgoing phase are rooted in fundamental science, they hold strong potential for broader impact.

In particular, the study of the CISS effect in donor–acceptor dyads can influence the field of organic solar cells, where electron-transfer pathways and spin management are central to achieving efficient and stable devices. Moreover, the results have direct relevance for quantum technologies based on molecules. The interplay of light, chirality, and spin opens new opportunities for spin initialization and readout of molecular qubits, even at room temperature.

Building on the success of my Marie Curie work, I plan to extend these studies to fully explore their technological potential. In the coming years, I have secured prestigious funding to establish a strong research group and new laboratories. My next steps will include the development of optoelectronic devices based on the molecular building blocks studied during PHOTOCODE, with applications in organic photovoltaics, renewable energy generation, and spintronics. In parallel, I will further investigate porphyrin-based molecular platforms for quantum information science, with a focus on practical implementations.

This program of work will bridge the fundamental advances achieved in my Marie Curie fellowship with more applied technologies, paving the way toward long-term commercialization. To support this transition, I will leverage the research environment of the University of Florence — host of my return phase — ensuring access to the necessary resources for further research, prototyping, IPR support, and technology transfer.