Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High open-circuit voltage in transition metal dichalcogenide solar cells   The conversion efficiency of ultra-thin solar cells based on layered
materials has been limited by their open-circuit voltage, which is typically
pinned to a value under 0.6 V. Here we report an open-circuit voltage of 1.02 V
in a 120 nm-thick vertically stacked homojunction fabricated with
substitutionally doped MoS2. This high open-circuit voltage is consistent with
the band alignment in the MoS2 homojunction, which is more favourable than in
widely-used TMDC heterostructures. It is also attributed to the high
performance of the substitutionally doped MoS2, in particular the p-type
material doped with Nb, which is demonstrated by the observation of
electroluminescence from tunnelling graphene/BN/MoS2 structures in spite of the
indirect nature of bulk MoS2. We find that illuminating the TMDC/metal contacts
decreases the measured open-circuit voltage in MoS2 van der Waals homojunctions
because they are photoactive, which points to the need of developing
low-resistance, ohmic contacts to doped MoS2 in order to achieve high
efficiency in practical devices. The high open-circuit voltage demonstrated
here confirms the potential of layered transition-metal dichalcogenides for the
development of highly efficient, ultra-thin solar cells.

13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-th