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PhD thesis defense of Roald Herckens

PhD thesis defense of Roald Herckens

Sep 24, 2019 - 15.00 uur

Universiteit Hasselt

campus Diepenbeek

Agoralaan Gebouw D

3590 Diepenbeek

Lokaal auditorium H4


De heer Roald HERCKENS



Roald Herckens invites you to the public defense of his doctoral thesis entitled:

"Synthesis of organic ammonium salts and their self-assembly in low-dimensional hybrid organic-inorganic perovskites".

Promoter is Prof. Dr. Dirk Vanderzande.

Copromoters are Prof. dr. Wouter Maes and dr. Laurence Lutsen.


Material properties have a major influence on the development of applications and their potential features. In this way, material design has a large impact on the ongoing progress in countless technological fields. Perovskites are a class of materials with a variety of remarkable properties depending on the chemical composition. In the case of lead-halide organic-inorganic hybrid 3D perovskites, a subclass of these materials, a number of features render them a suitable candidate for photovoltaics. Solar cells based on these materials have reached power conversion efficiencies up to 25.2%. Presently, one of the key challenges in this field is the limited stability of these solar cells. The goal of the work in this thesis was to overcome the stability issues surrounding hybrid perovskite materials and to further broaden the scope of the material class. These objectives were explored by performing cation substitutions and by lowering the dimensionality of the material, with a strong focus on two-dimensional (2D) hybrid organic-inorganic perovskites.

In this work, a selection of organic ammonium salts was synthesized and incorporated in 2D perovskites. The stability of solar cells based on these materials was thereby significantly enhanced. Additionally, the tunability of these hybrid perovskites was broadened by incorporating a variety of functional organic compounds in low-dimensional perovskites. The thermal behavior of the materials was linked to the structure of organic layer. Finally, an additional degree of complexity was introduced in the organic layer by applying charge-transfer complexes in the perovskite structure. The resultant material serves as a proof-of-concept which greatly increases the versatility of the material class.

The results of this work emphasize the flexibility of this material class and the tunability of the material properties. Applying functional organic structures in low-dimensional perovskites can lead to materials where the organic and inorganic layer have synergistic properties.