FWO travel credit for participating in a conference abroad at '2019 MRS Fall Meeting & Exhibit' Boston USA 01-06 / 12/2019 (R-10781)

In 2015 a new field of research, namely organic-inorganic hybrid perovskites to be used as semiconductors for thin-film electronic devices, was started within the group. After one year of exploratory research to get acquainted with the field we decided to focus on low-dimensional hybrid perovskites in which larger conjugated chromophores potentially acting as semiconductors are incorporated by self-assembly using the inorganic scaffold as a template. In this way the organic chromophores confined between the sheets of the inorganic layer, can take an organization for the organic chromophores that resemble the order observed in a single crystal. The number of inorganic sheets can easily be tuned by changing the stoichiometry of the organic small and large building blocks. In this way, a fluent transition of electro-optical properties can be achieved of the inorganic part from confined 2D structures to strongly delocalized quasi-3D structures. We extended this concept not only to organic chromophores but also to organic charge-transfer complexes. For all these concepts proof-of-concept have been delivered in the last few years. These are concepts that are either scarcely investigated or totally new, respectively. The potential value of the research results is high for thin-film electronics or even optoelectronics, given the versatility of the concept and the wide variation in building blocks that can be used. Actually, it is an effort to merge the world of inorganic perovskite semiconductors with the world of organic semiconductors and given the novelty the impact for future technological developments is high. The new concept that will be presented allows for creating a wide variation of essentially 2D layered structures using larger organic building blocks. For example, the use of carbazole ammonium salts in 2D hybrid perovskites leads to materials for solar cells with enhanced photoconductivity and stronger resistance toward moisture yielding solar cells with strongly enhanced stability compared to the reference 3D MAPI perovskite material [1]. Also, the use of pyrene ammonium salts to synthesize 2D hybrid perovskites has been explored. Transitions between 1D and 2D structures were observed by specific modification of the stoichiometry of the components and also in function of temperature. A detailed analysis of the stability under thermal stress has been reported [2]. In combination with the introduction of extra secondary interactions in the organic layer, a material is obtained with an exceptionally low bandgap, only 1 eV. This was realized by intercalating strong electron acceptor molecules (e.g. TCNQ and TCNB) in the organic layer. The pyrene chromophore acting as a donor together with TCNQ or TCNB leads to the formation of an organic charge transfer complex between the inorganic sheets. As well formation of 1D and 2D structures was observed depending on processing conditions [3, 4]. In the most recent work we are exploring mono tethered oligo-thiophene ammonium salts as building blocks for low dimensional hybrid perovskites. In conclusion, a new group of truly organic-inorganic hybrid materials is disclosed with possibly new applications for thin film electronics.

Keywords:POLYMER KINETICS

Disciplines:Physical chemistry of materials, Supramolecular chemistry, Synthesis of materials, Organic chemical synthesis, Physical organic chemistry