Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exciton Regeneration at Polymeric Semiconductor Heterojunctions   Control of the band-edge offsets at heterojunctions between organic
semiconductors allows efficient operation of either photovoltaic or
light-emitting diodes. We investigate systems where the exciton is marginally
stable against charge separation, and show via E-field-dependent time-resolved
photoluminescence spectroscopy that excitons that have undergone charge
separation at a heterojunction can be efficiently regenerated. This is because
the charge transfer produces a geminate electron-hole pair (separation
2.2-3.1nm) which may collapse into an exciplex and then endothermically
(E=100-200meV) back-transfer towards the exciton.

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The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
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The categories of this paper are: eess
16
The categories of this paper are: stat
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph