Discovery of New Singlet Fission Materials

After few decades of investigations just a handful of materials undergoing singlet fission are known despite the strong interest for fundamental science (photophysics, quantum dynamics, quantum chemistry) and the acknowledged potential for technological applications in photovoltaics and other optoelectronics devices. The limited number of available materials is very concerning because one needs a large pool of compounds to optimize device performance, processing and integration with other materials. Moreover, the fundamental understanding is severely limited when the systems that can be studied are so few.

This proposal will address the key limitation of the field, identifying a set of materials suitable for singlet fission by an innovative high-throughput computational screening approach. For all the new candidates found within this project a synthetic route is available and the crystal structure is known, i.e. the prediction will be about EXISTING MOLECULAR MATERIALS rather than hypothetical molecules. Unsuitable molecular arrangements in the crystal are taken into account and all the criteria for singlet fission can be imposed in parallel. The prediction will be accompanied by a level of confidence obtained by calibrating the method against a large number of know experimental data (Objective 1).

Our preliminary work on a small sample of the compounds to be screened and on the calibration of the methodology has already led to the discovery of few highly promising candidates. Our projections indicate that more than a hundred new molecules (not already known to undergo singlet fission) can be discovered in this way.

The computational screening is followed by a thorough post-processing analysis to identify new design rules for singlet fission and assess the validity of the old ones. These rules will guide the development of new singlet fission materials from the lead compounds identified by this work (Objective 2).

The preliminary experimental validation of the prediction is part of this project (Objective 3). A small sub-set of molecules to be characterized optically will be selected among those easier to obtain from collaborators or commercially. The optical characterization will be performed by our partner Prof. S. Reineke (TU, Dresden).

The UK has invested vigorously in all aspects of organic electronics and the field is mature enough that many initiatives are currently focusing on value-creation. With economic benefits and the potential societal impact already well recognized, this proposal envisions two paths to maximize its impact.

INTELLECTUAL PROTECTION OF PROMISING MATERIALS. The set of molecules for singlet fission is of obvious commercial value because intellectual protection can be sought for materials that are not already patented as singlet fission materials and one can include chemical variations of lead compounds that are likely to display similar characteristic. As part of our impact plan, we will seek exploitation of the newly discovered molecules in collaboration with the Liverpool IP team and involving at the appropriate time an external private sector partner.

DATABASE & KNOWLEDGE. A database of computed excited states electronic structures can be invaluable for optoelectronic research as many interesting questions can be asked and answered by a simple database search. R&D teams can be interested in a particular set of energy levels, polarity, functional groups and can see how often that set of features is present in the database. This tool can be made available at a nominal fee (to support its maintenance) to the academic community and will be licenced to the private sector. It should be noted that such database is not just for singlet fissions but for any properties involving singlet or triplet excited states, including most problems of contemporary relevance to OLED, one of the most commercially successful area of organic electronics.

The key results of this research will be published in peer reviewed journals with very high impact publications expected. The scientific training into a novel combination of computational chemistry, solid state physics and data science will enhance the career prospects of the PDRA. When combined with the training programme in professional skills, available within the host institution, the project will facilitate the emergence of new leaders in computer aided materials discovery.