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PhD thesis defense of Dries Devisscher

PhD thesis defense of Dries Devisscher

Oct 11, 2019 - 13.00 uur

Universiteit Hasselt

campus Diepenbeek

Agoralaan Gebouw D

3590 Diepenbeek

Lokaal auditorium H4


De heer Dries DEVISSCHER



Dries Devisscher invites you to the public defense of his doctoral thesis entitled:

"Insights in molecular interactions in bulk heterojunction organic solar cells by synthesis of novel electron donor materials".

Promoter: Prof. Dr. Wouter Maes

Copromoter: Prof. Dr. Peter Adriaensens and Dr. Laurence Lutsen


With the negative consequences of global warming becoming increasingly apparent, the pressure is mounting to shift our society away from carbon intensive energy sources. Even though solar electricity generation has increased tremendously over the past decades, it is clear new and existing photovoltaic applications still have a lot of untapped potential. Among the emerging solar cell technologies, organic photovoltaics (OPV) are interesting due to the high chemical tuneability of the active layer components, the ability to be printed from solution on inexpensive flexible substrates, a good performance in low light conditions and a high power/weight ratio. Due to the rapid increase of the power conversion efficiency (PCE) of bulk heterojunction (BHJ) OPV devices in recent years, particularly by the development of novel non-fullerene acceptors, the commercialization of OPV applications is closer than ever. Nonetheless, some fundamental aspects regarding the influence of the chemical structure of the active layer components on the donor:acceptor interface and nanoscale morphology remain to be unraveled. As the photoactive layer in BHJ OPV devices consists of two finely intermixed components, an electron donor and an electron acceptor, the molecular arrangement of these materials on the nanoscale has a major influence on the underlying physical properties that govern processes such as exciton dissociation, charge separation and charge transport. In this doctoral thesis, a number of electron donating semiconducting materials were developed, designed to afford insights into the structure-property relationships governing the donor-acceptor interactions present in BHJ OPV blends. In particular, the impact of solubilizing alkyl side chain length, halogen atom substitution, increased planarization and donor:acceptor ratio were studied for a number of different OPV systems. The combination of several dedicated analyzation techniques including sensitive external quantum efficiency measurements and proton wideline solid-state NMR provided essential information, allowing further understanding of several important aspects influencing OPV device efficiency. Although no direct attempts at improving the applicability were made, these enhanced fundamental insights will ultimately aid in the commercialization of OPV. In combination with other existing and new renewable energy technologies, the emergence of OPV will contribute to the solution to the energy crisis that mankind is facing in the 21th century.