Organic light-emitting diodes (OLEDs) have become a dominant technology in the display industry and hold great promise for a variety of applications in the fields of lighting, visible communication, sensing and healthcare. Current research efforts focus on the development of thermally-activated delayed fluorescent (TADF) emitters that promise highly efficient and long-lifetime performance without the use of any heavy metals. These materials show a small energy gap between their singlet and triplet energy levels allowing the up-conversion of non-emissive triplets to light-emitting singlets at room temperature via the reverse intersystem crossing process. Although efficient triplet harvesting can take place in TADF OLEDs, the dynamics involved in the TADF mechanism need to be faster to substantially reduce the accumulation of long-lived triplet excitons during the device operation and improve their overall performance. This project addresses this research challenge by proposing an innovative approach based on the integration of sub-wavelength photonic nanostructures into TADF OLEDs. Via their effects on the local photonic density and the dielectric permittivity of the effective media, the photonic nanostructures will be engineered to accelerate both radiative decay and reverse intersystem crossing rates. This will improve the efficiency of OLEDs, especially at high brightness and increase their lifetime. The successful outcome of the project is expected to lead to an improvement of the TADF OLED technology and will be highly relevant for a range of other applications in fields as diverse as organic optoelectronics, sensing and photochemistry.

Mathematics is the language of science and hence is universal. On the other hand, mathematics is also part of culture, and one notices important cultural differences in the historical development of mathematics in Japan and in the Netherlands. Despite the globalization and the internationalization of science, many of these aspects are visible even today. In our opinion, bringing together two different mathematical traditions is highly beneficial. This difference in style is largely present today in the respective communities in the Netherlands and Japan. However, there are also methods and techniques that develop in parallel (e.g., lace expansions, large deviations). Scientific discussions, exchange of ideas, and collaboration between the communities is already present on the individual level but there is a definite need, and in fact, some urgency, to bring the cooperation and collaboration on a higher level. In both countries, we currently have a surprisingly strong upcoming generation of talented young researchers. Now is the right moment to create the necessary momentum for the training of the next generation and to shape the future collaboration between the communities. It is important to add that in the field of probability theory Japan and the Netherlands both have a very prominent position, and are able to compete with mathematical “superpowers” like the US and France. With the present application, our primary objective is to facilitate collaboration between the two communities. In fact, we plan that the Japan-Netherlands Seminar in Probability will become a regular event, alternating between the two countries every 1-2 years.

This travel grant will enable Prof. Stephen Eichhorn (University of Bristol) to undertake collaborative work together with Prof. Tetsuo Kondo (Kyushu University, Japan) in the area of hydrophobic interactions in cellulose nanofibres. Cellulose is the most utilised material on the planet. Current annual production stands at a staggering 10^12 tonnes. Given its density this is about 20 times the volume of steel. It is primarily produced by plant cell walls but can also by some gram-negative bacteria and one known animal (tunicates). The structure of cellulose is such that chemical groups which decorate the sugar units making up the chains of the polymeric structure, are involved in hydrogen bonding - like in ice. This presents a dichotomy, in that although the basic sugars that make up cellulose are soluble in water, the polymer cellulose is not. This is usually attributed to the extensive hydrogen bonding present but given that the material will not dissolve in most solvents, this is now thought to not be the only contributing factor. Recently, the concept of a hydrophobic interaction (where two water 'hating' surfaces come together) within the cellulose structure, between the faces of the glucose rings, has been postulated - the so-called 'Lindman effect - as a limiting factor in its solvation. The hydrophobic effect itself is well-understood for relatively simple molecules, but for cellulose and complex macromolecules our understanding is still very much in development. Better understanding of this effect in cellulose could lead to greater exploitation of the material, particularly its use in composites by exploiting the inherent hydrophobicity of certain surfaces of a new form of cellulose nanofibre (a fibre with lateral dimensions <100nm). This form of cellulose nanofibre is produced by the group at Kyushu University using high pressure water jets - called Aqueous Counter Collision. The purpose of this grant is to form a collaboration to better understand the properties of this material. Professor Eichhorn currently has a large EPSRC funded program of research investigating the formation of hydrogels (EP/N03340X/2) using cellulose nanofibers; one potential area of exploitation is their use in composite materials. Professor Kondo has just received funding from NEDO (New Energy and Industrial Technology Development Organization)- Feasibility Study Program to study the interaction of thermoplastic polymers with cellulose. The work from these grants, combined with this travel, will enable the group to establish some new research lines in this area.