Proceedings of nanoGe Fall Meeting 2021 (NFM21)
DOI: https://doi.org/10.29363/nanoge.nfm.2021.027
Publication date: 23rd September 2021
Halide double perovskites are an emerging class of materials with considerable structural and electronic diversity [1, 2, 3] and reliable stability towards heat and moisture under ambient conditions. We have recently shown that silver-pnictogen double perovskites, e.g. Cs2AgBiBr6, a material with promising optoelectronic properties, exhibit non-hydrogenic and strongly localized resonant excitons. This finding can be traced back to their chemical heterogeneity that leads to anisotropic effective masses and local field effects [4].
In this contribution, we systematically investigate how the electronic and optical excitations in halide double perovskites are impacted by the band edge orbital character. We use ab initio many-body perturbation theory within the GW approximation [6] and the Bethe-Salpeter equation [5] to compute excitations of a group of double perovskites with different valence and conduction band orbital character (Cs2AgBiCl6, Cs2AgInCl6, Cs2BiInCl6). We find that contrary to Cs2AgBiCl6, Cs2AgInCl6 and Cs2BiInCl6 exhibit delocalized excitonic states with low binding energy. Furthermore, carrier effective masses are highly isotropic and local field effects small, which we attribute to the orbital character at the band edges of these direct band gap semiconductors. Our results contribute to a detailed atomistic understanding of the light-matter interactions in chemically heterogeneous double perovskites and highlight the potential of these materials for light harvesting applications.
This work was supported by the Bavarian State Ministry of Science and the Arts through the Collaborative Research Network Solar Technologies go Hybrid (SolTech), the Elite Network Bavaria, the German Research Foundation (DFG) through SFB840 B7, the UK Engineering and Physical Sciences Research Council (EPSRC), and the Oxford University Press John Fell Fund. The authors would like to acknowledge computational resources at the Dutch national supercomputer Cartesius with the support of SURF Cooperative, MESA+ Institute of Nanotechnology and the Texas Advanced Computing Center (TACC) at UT Austin via the NSF funded XSEDE program.
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