Dynamics of singlet and triplet excitons in organic semiconductors

PhD ceremony: Mr. O.V. Mikhnenko, 14.30 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Dynamics of singlet and triplet excitons in organic semiconductors

Promotor(s): prof. M.A. Loi, prof. P.W.M. Blom

Faculty: Mathematics and Natural Sciences

Organic semiconductors open the door to new applications in electronics and optoelectronics where low costs, light weight, and biocompatibility are more important than durability and high performance. For instance, organic light-emitting diodes and solar cells can be integrated into clothing, newspapers, windows, etc. The working principle of these devices relies on the creation and recombination of excitons – nanometer-sized and electrically neutral quasiparticles that carry useful energy. Excitons in organic semiconductors can be viewed as strongly bound pairs of positive and negative elementary charges. In organic solar cells, the energy of absorbed light is transported by excitons to a specially designed interface, where they decompose into positive and negative charges leading to the generation of electrical current. Therefore, the motion of excitons – exciton diffusion – is a very important process. In particular, it is crucial to know how far excitons can diffuse for the design of solar cells. This thesis focuses on exciton diffusion in organic semiconductors and on related phenomena. The main achievements that are described here are twofold. (i) We have developed two new methods to measure the exciton diffusion parameters and (ii) we have used these tools to improve our understanding of excitonic processes in organic semiconductors.