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Influence of the Iodide to Bromide Ratio on Crystallographic and Optoelectronic Properties of Rubidium Antimony Halide Perovskites
journal contribution
posted on 2018-12-07, 00:00 authored by Stefan Weber, Thomas Rath, Kathrin Fellner, Roland Fischer, Roland Resel, Birgit Kunert, Theodoros Dimopoulos, Andreas Steinegger, Gregor TrimmelRubidium antimony
halides are a promising low toxic alternative to organo-lead halide
perovskites as photovoltaic material. In this contribution, we systematically
investigate the influence of varying the bromide to iodide ratio on
the structural, optical, and photovoltaic properties of Rb3Sb2Br9–xIx (x = 0–9). Single
crystal data reveal that all compounds crystallize in a 2D-layered
monoclinic crystal structure. Sequential substitution of iodide with
the smaller bromide does not change the crystal system; however, increasing
the bromide content results in a shrinkage of the unit cell as well
as in a blue shift of the absorption onset, increasing the band gap
from 2.02 to 2.46 eV. Whereas the photovoltaic properties of bromide
rich compounds are limited due to a preferential orientation of the
layered structure parallel to the substrate, which is detrimental
to charge transport, solar cells with Rb3Sb2I9 as absorber material display power conversion efficiencies
of 1.37%. Moreover, the devices exhibit low hysteresis properties
and are stable for more than 150 days stored under inert atmosphere.