Perovskite-Inspired 2D Antimony-Based Absorber Layers for Optoelectronic Applications
Nadja Giesbrecht a, Andreas Weis a, Thomas Bein a
a Ludwig-Maximilians-Universität München, Department Chemie, Germany, Butenandtstraße, 5-13, München, Germany
Oral, Nadja Giesbrecht, presentation 027
Publication date: 25th November 2019

The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications due to toxicity and instability issues. Therefore, perovskite-inspired new lead-free compounds are sought-after as new candidates for photovoltaic applications. However, most of the suggested substitutions are either oxidation unsteady or suffer from indirect and wide bandgaps. Here, we demonstrate the first thin-film synthesis of a stable MA3Sb2I9 in the perovskite-like 2D polymorph with narrow and direct bandgaps. So far, the reported MA3Sb2I9 absorber layers only crystallized in the zero-dimensional dimer structure with wide indirect bandgap properties but already reached photovoltaic efficiencies above 2.8 %. Thus, after being successful with lead acetate for optimal film formation,[1],[2] we introduce a crystallization process based on antimony acetate precursor and sustainable solvents like MeOH and EtOH for the application of the promising 2D polymorph in solar cells. To confirm the improved absorption properties in the layered structure, we investigated the electronic band structure and experimentally verified the presence of a semi-direct bandgap at around 2.1 eV. Using in situ XRD methods, we validate the stability of the layered phase towards high temperature and moisture. With the incorporation of two-valent metal cations, we show how the bandgap in the layered structure narrows further, revealing a new class for promising lead-free absorber layers. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.

The authors are grateful for funding from the Clusters e-conversion and NIM (German Research Foundation, DFG).

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