Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optoelectronic Properties and Defect Physics of Lead-free Photovoltaic
  Absorbers Cs$_2$Au$^{I}$Au$^{III}$X$_6$ (X=I, Br)   Stability and toxicity issues with the hybrid lead iodide perovskite
MAPbI$_3$ necessitate a hunt for potential alternatives. Here, we shed light on
promising photovoltaic properties of gold mixed-valence halide perovskites
Cs$_2$Au$_2$X$_6$ (X = I, Br, Cl). They satisfy fundamental requirements such
as nontoxicity, better stability, a band gap in the visible range, and a low
excitonic binding energy. Our study shows a favorable electronic structure,
resulting in a high optical-transition strength, and thus a sharp rise in the
absorption spectrum near the band gap. This, in turn, yields a very high
short-circuit current density and hence higher simulated efficiency compared
with MAPbI$_3$. However, careful investigation of defect physics reveals the
possibility of deep-level defects (such as V$_X$ , V$_{Cs}$, X$_{Au}$,
X$_{Cs}$, Au$_i$, and Au$_X$ , X = I, Br), depending on the growth conditions.
These can act as carrier traps and become detrimental to photovoltaic
performance. The present study should help in taking necessary precautions in
synthesizing these compounds in a controlled chemical environment, which should
minimize performance limiting defects and pave the way for future studies on
this class of materials.

35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
2
The categories of this paper are: math