Investigation of Triple Cation Tin Perovskite Solar Cells
Gregor Trimmel a, Thomas Rath a, Stefan Weber a, Jasmin Handl a, Theodoros Dimopoulos b, Birgit Kunert c
a Institute for Chemistry and Technology of Materials (ICTM), NAWI Graz, Graz University of Technology, Stremayrgasse 9, Graz, 8010, Austria
b AIT Austrian Institute of Technology, Center for Energy, Photovoltaic Systems, Vienna Austria
c Institute of Solid State Physics, Graz University of Technology, Austria
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Gregor Trimmel, 142
Publication date: 11th February 2019

In the last years, tin perovskites have shown to be the most promising alternative to lead perovskites and power conversion efficiency values of above 9% have now been reached. Similar to lead based materials, key parameters for further improvements of tin perovskite solar cells are in the optimisation of the chemical composition by varying both, A-cations as well as the halogenide X-anions as well as in the optimisation of the layer formation. In this contribution, a novel triple cation tin perovskite MA0.75FA0.15PEA0.1SnI3 (methylammonium (MA), formamidinium (FA) and phenylethylammonium (PEA)), which was stabilized with 10% SnF2, was investigated exhibiting superior photovoltaic properties than the corresponding double cation-perovskites in our device setup. In comparison to the FA-PEA compound, this MA rich perovskite has an extended absorption and photocurrent generation up to a wavelength of 1000 nm. Based on the XRD-data, a mixed 2D/3D structure was identified, similar to the already known FA-PEA compound. Also in this material, the processing parameters such as spin coating conditions, anti-solvent dripping, as well as annealing are of crucial importance leading to solar cells with power conversion efficiencies up to 5.0% (measured with a shadow mask) and notably good stability under glovebox conditions. After more than 5000 hours, the devices exhibit still 87% of the initial efficiency. Furthermore, we investigate the incorporation of bromide into this triple cation tin iodide perovskite by the partial substitution of iodide yielding MA0.75FA0.15PEA0.1SnBrxI3−x (x = 0 – 1). As expected, this substitution leads to an increase of the band gap as well as an enhanced open circuit voltage. Increasing the bromide content above x = 1 yields thin films with pinholes resulting in lower device performance and large hysteresis.

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