PhD thesis defense of Gaël Heintges
Oct 17, 2019 - 13.30 uur
TU Eindhoven, 5612 AZ Eindhoven, Nederland
Lokaal Atlas 0.710
Gaël Heintges invites you to the public defense of his doctoral thesis entitled:
"Influencing the photovoltaic properties and aggregation of diketopyrrolopyrrole based polymers via structural modification".
Promoter: Prof. Dr. Wouter Maes - UHasselt
Copromoter: Prof. Dr. Ir. René Janssen - TU/e
Organic solar cells are an attractive technology in which organic materials are used to harvest light. These solar cells can be made lighter, in many colours and even semi-transparent, opening up new applications such as building integration. The active layer in these cells is generally comprised of two materials: an electron donor, which in our case is a semi-conducting polymer, and an electron acceptor, in our case a fullerene derivative. The energy levels of both materials can be tuned to achieve the best photovoltaic efficiency. Also the morphology of the active layer, i.e. the extent to which both materials mix, is crucial to achieve a high efficiency.
In this thesis, diketopyrrolopyrrole based polymers were developed for use as electron donors in organic solar cells. By tuning the aggregation properties of the material, control over the active layer morphology could be achieved. It was found that introducing branching into the polymer architecture had a dramatic effect on the solubility of the polymer and photovoltaic efficiency of the solar cells. Also changing the branching point in the solubilizing alkyl side-chain proved to have a large effect. In both cases, it was impossible to separate the effects of intrinsic solubility of the monomers from the influence of molecular weight. This was however made possible by producing a series of siloxane substituted polymers. Here, we found that the molecular weight can have a larger effect on the morphology formation than the intrinsic solubility. Finally, the influence of a terpolymer design on the energy levels of the material and photovoltaic properties was investigated.