Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dark Self-Healing Mediated Negative Photoconductivity of Lead-Free
  Cs3Bi2Cl9 Perovskite Single Crystal   Halide perovskites are recently emerged as one of the frontline
optoelectronic materials for device applications and have been extensively
studied in past few years. Among these while, lead-based materials were most
widely explored, investigation of optical properties of lead-free perovskites
is limited. Being optically active, these materials were expected to show
light-induced enhanced photoconductivity and the same was reported for lead
halide perovskite single crystals. However, on contrary, herein, light-induced
degradation of bismuth halide perovskite Cs3Bi2Cl9 single crystals is reported
which was evidenced by negative photoconductivity with slow recovery. The
femtosecond transient reflectance (fs-TR) spectroscopy studies further revealed
these electronic transport properties were due to the formation of
light-activated metastable trap states within the perovskite crystal. The
figure of merits of Cs3Bi2Cl9 single-crystal detectors such as responsivity (17
mA/W), detectivity (6.23 X 10power 11 Jones) and the ratio of current in dark
to light (~7160) was calculated and it is found that they are comparable or
higher to reported perovskite single crystals based positive photodetectors.
This observation for lead-free perovskite single crystals which were optically
active but showed retroactive photocurrent on irradiation remained unique for
such materials.

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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: eess