Extending the Functionality of the Organic Layer in 2D Hybrid Perovskites
María C. Gélvez-Rueda a, Ferdinand C. Grozema a
a Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
nanoGe Perovskite Conferences
Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
International Conference on Perovskite Thin Film Photovoltaics
Jerusalem, Israel, 2019 February 24th - 27th
Organizers: Lioz Etgar and Kai Zhu
Oral, María C. Gélvez-Rueda, presentation 042
DOI: https://doi.org/10.29363/nanoge.nipho.2019.042
Publication date: 21st November 2018

2D hybrid perovskites are a promising class of materials for optoelectronic applications such as light emitting diodes, photodetectors and solar cells. Compared to the more researched 3D hybrids they have several advantages, including an improved stability in ambient conditions and the possibility of introducing functionality in the organic layer. So far, the organic layer is only used to tune their band gap, dielectric environment and dimensionality, while the transport of charge carriers remains restricted to the inorganic metal-halide octahedrals. In this work we aim at introducing functionality in the organic layer for instance to improve charge separation or tune the sensitivity of photodetectors.  In general, there is a lack of understanding on how the organic cations affect the charge and excited state dynamics of 2D hybrid perovskites and whether the transport can be extended to the organic layer. In this work we use unique time-resolved microwave conductivity techniques, combined with time-resolved fluorescence and femtosecond transient absorption to study the charge and excited state dynamics of a large variety of 2D organic-inorganic perovskites. First, we have found that the thickness of inorganic layers highly affects properties such as mobility, yield of charge dissociation, exciton binding energy. Second, pure 2D perovskites (n=1) with different organic groups (BA, BZA, HA) exhibit new electronic transitions at low temperature that may be associated with different nature of the excitonic states (free exciton, biexcitons, trions). Finally, we have explored the possibility to adapt the organic cations, so that they start playing a role in defining the opto-electronic properties. It is, for example, possible to improve the charge transport to the organic layer through the formation of charge-transfer complexes between a charge-donating and charge-accepting molecule. We synthesized 2D hybrid perovskites containing a donor molecule (Pyr-C4-NH3+), which serves as a reference material, but with improved transport between the inorganic layers.  And subsequently, we intercalated strong electron acceptors (TCNQ and TCNB), leading to the formation of charge-transfer complexes with the Pyr-C4-NH3+ donor molecules. We will present several examples where the organic cation affects the charge transport properties, the dissociation of exciton and the optical properties.

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