Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dipolar cation accumulation at interfaces of perovskite light emitting
  solar cells   Ionic migration in organo-halide perovskites plays an important role in
operation of perovskite based solar cells and light emitting diodes. Despite
the ionic migration being a reversible process, it often leads to worsening of
perovskite based device performance, hysteresis in current-voltage
characteristics, and phase segregation in mixed halide perovskites being as the
most harmful effect. The reason is in dynamical band structure changes, which
controllable engineering would solve one of the biggest challenges for
development of light-emitting solar cells. Here we demonstrate controllable
band bending due to migration of both cation and anion ions in mixed halide
perovskite devices. The band structure rearrangement is demonstrated in light
emitting solar cells based on the perovskite with organic cations
methylammonium (MA+) and formamidinium (FA+), possessing non-zero dipole
momentum of 2.29 and 0.21 Debye, respectively, and with PEDOT:PSS and C60
transport layers having a high barrier of 0.8 eV for charge injection. Under
applied external voltage MA+ and FA+ cations move towards the electron
transport layer and form a dipole layer at the perovskite/electron transport
interface, which lowers threshold voltage for electroluminescence down to 1.7 V
for MAPbBr2I and 2.6 V for FAPbBr2I, whereas monohalide perovskite MAPbBr3 does
not demonstrate such behavior. This ability to in-situ change the device band
structure paves the way developing of dual-functional devices based on simple
design. It also makes mixed halide perovskites more flexible than mono halides
ones for developing different optoelectronic devices without the use of special
types of work function modifying transport materials.

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The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
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The categories of this paper are: adap-org
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg