Tin Alloying in Layered MA3Sb2I9 Thin Films: Assessing the origin of enhanced absorption and stabilizing charge states
Andreas Weis a, Patrick Ganswindt a, Hannah Illner a, Clement Maheu b, Nadja Glück c, Shizhe Wang a, Florian Wolf a, Rik Hooijer a, Thomas Mayer b, Thomas Bein a
a University of Munich (LMU), Department of Chemistry and Center for Nanoscience (CeNS), 81377 Múnich, Alemania, Múnich, Germany
b TU Darmstadt, Surface Science, Jovanka-Bontschits-Str. 2, Darmstadt, 64287, Germany
c Department of Materials Science and Engineering, Monash University, Clayton, Victoria, 3800 Australia, Wellington Rd, Clayton, Australia
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Poster, Andreas Weis, 251
Publication date: 20th April 2022

Heteroatom alloying of lead-free perovskite derivates was shown to be a highly promising route to circumvent some of the problems this class of materials faces for application as optoelectronic material. Here, we demonstrate the first, facile solution-based synthesis of Sn-alloyed layered MA3Sb2I9 thin films by precursor engineering, combining acetate and halide sources. An increasing concentration of tin halides in different oxidation states leads to a boost in absorption over the whole visible spectrum. We demonstrate phase pure synthesis with homogeneous thin film morphologies and elucidate the heterovalent incorporation of Sn into the MA3Sb2I9 lattice, proving the formation of additional states in the bandgap by theoretical calculations. With this, we dissect the absorption increase into three singular components which we attribute to Sn intervalence and Sb-Sn “defect-to-band” transitions. Finally, we show the charge-stabilizing effect of the system through robustness towards precursors in mixed oxidation states, discussing the ambiguous formal oxidation state and trace the improved ambient stability of this material back to this property.

The authors acknowledge funding from the Bavarian Network “Solar Technologies Go Hybrid”, the German Science Foundation (DFG) focus program SPP 2196 and the DFG Excellence Cluster e-conversion (EXC 2089/1-390776260). The authors thank Dr. Steffen Schmidt for performing the SEM measurements.

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