In control of exciton and charge dynamics in molecular crystals

Información del proyecto

ICONICAL

Identificador del acuerdo de subvención: 648433

DOI

10.3030/648433

Proyecto cerrado

Fecha de la firma de la CE 28 Mayo 2015

Fecha de inicio 1 Junio 2015

Fecha de finalización 31 Mayo 2020

Financiado con arreglo a

• EXCELLENT SCIENCE - European Research Council (ERC)

Coste total

€ 2 000 000,00

Aportación de la UE

€ 2 000 000,00

Coordinado por

TECHNISCHE UNIVERSITEIT DELFT
Netherlands

Periodic Reporting for period 4 - ICONICAL (In control of exciton and charge dynamics in molecular crystals)

Período documentado: 2019-12-01 hasta 2020-05-31

Resumen del contexto y de los objetivos generales del proyecto

It is the aim of the work proposed here to achieve control over charge and excited state dynamics in organic crystalline materials and in this way to come to solid state materials with explicit built-in functionality. The charge and excited state dynamics do not only depend on the properties of individual molecules but are to a large extent determined by the interactions between multiple molecules. By careful engineering of the properties of individual molecules and of the way they aggregate in the solid state crystalline materials it is in principle possible to design materials that exhibit a specific functionality. Examples of this are materials that are optimized to give high charge carrier mobilities and high exciton diffusion coefficients. Both of these properties are of direct relevance for electronic devices based on these materials, such as photovoltaic cells and light-emitting diodes. It is also possible to design more complex functionality in these materials. A first example of this is singlet exciton fission, a process by which one singlet excited state transforms into a combination of two triplet states. This spin-allowed process is of considerable interest in organic photovoltaics since it can in principle increase the maximum thermodynamic efficiency by a factor 1.5. A second example of complex functionality is upconversion of low energy photons into higher energy photons. This is possible by combining two low-energy triplet excited states into a single singlet excited state by triplet-triplet annihilation. The latter is the reverse process of singlet exciton fission.

A successful implementation of these ideas can lead to a substantial improvement in the efficiency of solar cells based on organic materials and more efficient organic electron devices. This will benefit society in terms of a cleaner generation of electricity and more energy-efficient devices.

Trabajo realizado desde el comienzo del proyecto hasta el final del período abarcado por el informe y los principales resultados hasta la fecha

During this project we have made significant progress in control the opto-electronic properties of crystalline materials. During the 5 years of the project we have:
- unraveled the relation between solid state packing and the charge transport properties
- obtained significant new insight in the mechanism of singlet fission andd the relation between molecular structure and solid state packing and the efficiency of singlet fission
- achieved a theoretically proposed new device structure for photo-chemical upconversion of red photons followed by direct extraction of electrons
- established a new research direction involving the incorporation of large conjugated organic chromophores into 2D pervoskite structures. This has uncovered many new interesting directions to incorporate new functionality in these materials.
The research has led to the publication of over 30 peer-reviewed scientific papers, several of them in high-impact journals. Several publications on the final results are still in preparation.

Avances que van más allá del estado de la técnica e impacto potencial esperado (incluida la repercusión socioeconómica y las implicaciones sociales más amplias del proyecto hasta la fecha)

The work in the project has led to several publications in high impact journal such as Nature Chemistry and Nature Materials. These contribution are clearly pushing the boundaries of knowledge in design and characterisation of solar cell materials. In addition, during the project we have significantly expanded the scope by also studying hybrid organic/inorganic pervskite materials with a specific focus on materials where the organic part is key in determining the properties. We have been able to define clear guidelines related to the incorporation of large conjugated organic molecules, which are the key subject of the project, into hybrid perovskite materials and in this way introduce new properties. No socio-economical or wider societal implications have emerged from the project so far.

Mechanism of singlet fission in crystalline materials