Proceedings of nanoGe Fall Meeting 2018 (NFM18)
DOI: https://doi.org/10.29363/nanoge.nfm.2018.238
Publication date: 6th July 2018
During the last years, three-dimensional hybrid perovskites were in the spotlight because of their very promising properties as semiconductor materials for solar cells, but also for optoelectronic applications in general. Indeed, with a low temperature and precursor solution based synthesis and certified 20% photovoltaic efficiency, 3D hybrid perovskites have been claimed as the new big thing in photovoltaics1. Further studies must be conducted to understand in detail the properties of this material, but especially to overcome one of its main flaws: degradation issues.
Currently, two-dimensional hybrid perovskites are getting attention of the scientific community mainly due to two reasons: the improvement of the stability and the chemical composition versatility, much higher than for the 3D-peovoskites. In fact, in the 3D case, the size of the “cages” created by the octahedral network limits the candidates as organic/inorganic cation, which is not the case of layered 2D hybrid perovskites. With these materials, we are expending the field of possibilities and it can lead to better tunability of the photophysical properties.
We are reporting here (time-dependent) density functional theory calculations [(TD)-DFT] on alkyl-ammonium lead iodide perovskites, and more specifically, the influence of the alkyl chain length of the spacer cation on the electronic structure and optical properties of the material. We predicted significant changes using long or short chains. Indeed, if the inorganic layers fix the electronic properties, the length of the organic cation showed to have an indirect effect. With long alkyl chains, as dodecyl chains, an opening of the electronic band gap occurs, due to the influence of the supramolecular packing on the structure organization of the octahedra network. For the case of long organic spacer dodecylammonium lead iodide perovskites, organic chains adopt a polyethylene-like packing, causing distortions in the inorganic frame and leading to the observed electronic band gap opening. These theoretical results are in agreement with experimental data and demonstrate that organic saturated chains can modify the optoelectronic properties of layered halide perovskite semiconductors2.
1 J. Bisquert, Journal of Physical Chemistry Letters 4(15):2597, 2013
2 C.Quarti, et al., Journal of Physical Chemistry Letters, DOI: 10.1021/acs.jpclett.8b01309
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