Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sn/Ge substitution in
  ((C$_\textrm{n}$H$_{2\textrm{n}-1}$NH$_3$)$_2$PbI$_4$; n=3): An emerging 2D
  layered hybrid perovskites with enhanced optoelectronic properties$^\dag$   Two-dimensional (2D) perovskites show higher stability in comparison to their
three-dimensional (3D) counterparts. Therefore, 2D perovskites have invoked
remarkable attention in basic understanding of their physical properties and
optoelectronic applications. Here we present a low-dimensional naturally
self-assembled inorganic-organic (IO) hybrid systems based on primary cyclic
ammonium-based (C$_{\textrm{n}}$H$_{2\textrm{n}-1}$NH$_{3}$) semiconductor
series [viz. ((C$_{\textrm{n}}$H$_{2\textrm{n}-1}$ NH$_3$)$_2$PbI$_4$; n=3-6)].
However, the wide bandgap nature and presence of toxicity due to lead (Pb)
prohibit their applications. Therefore, in the present work, we study the role
of Ge/Sn substitution and Pb-vacancy (Pb-$\boxtimes$) to reduce concentration
of Pb and to enhance solar cell efficiency by the formation of mixed perovskite
structures. We have discussed the effect of spin-orbit coupling (SOC) using
state-of-the-art hybrid density functional theory (DFT). We find the mixed
conformers with Pb-$\boxtimes$ do not possess structural stability. Moreover,
they have indirect bandgap, which is not good for solar cell applications. Only
those conformers, which have favourable thermodynamics and structural
stability, are considered for further study of optical properties. Our results
infer that Sn substitution is more favorable than that of Ge in replacing Pb
and enhancing the efficiency. Exciton binding energies calculated using
Wannier-Mott approach for pristine and substituted conformers are larger than
lead halide perovskites, while the electron-phonon coupling is smaller in the
former. From computed spectroscopic limited maximum efficiency (SLME), these 2D
perovskites show enough promise as alternatives to conventional lead halide
perovskites.

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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: q-fin
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con