Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Functionality-directed Screening of Pb-free Hybrid Organic-inorganic
  Perovskites with Desired Intrinsic Photovoltaic Functionalities   The material class of hybrid organic-inorganic perovskites has risen rapidly
from a virtually unknown material in photovoltaic applications a short 7 years
ago into a ~20% efficient thin-film solar cell material. As promising as this
class of materials is, however, there are limitations associated with its poor
long-term stability, non-optimal band gap, presence of environmentally-toxic Pb
element, etc. We herein apply a functionality-directed theoretical materials
selection approach as a filter for initial screening of the compounds that
satisfy the desired intrinsic photovoltaic functionalities and might overcome
the above limitations. First-principles calculations are employed to
systemically study thermodynamic stability and photovoltaic-related properties
of hundred of candidate hybrid perovskites. We have identified in this
materials selection process fourteen Ge and Sn-based materials with potential
superior bulk-material-intrinsic photovoltaic performance. A distinct class of
compounds containing NH3COH$^+$ with the organic molecule derived states
intriguingly emerging at band-edges is found. Comparison of various candidate
materials offers insights on how composition variation and microscopic
structural changes affect key photovoltaic relevant properties in this family
of materials.

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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: astro-ph
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th