jp5b07059_si_001.pdf (2.22 MB)
Relationship between Carbon Nitride Structure and Exciton Binding Energies: A DFT Perspective
journal contribution
posted on 2015-11-12, 00:00 authored by Sigismund Melissen, Tangui Le Bahers, Stephan N. Steinmann, Philippe SautetGraphitic (g)-CxNyHz has become
a popular element in photocatalytic water splitting cells. Recently,
the crystal structures of completely polymerized g-C3N4 and incompletely polymerized g-C6N9H3 crystals based
on the triazine and heptazine monomers have been characterized. In
this manuscript we evaluate the atomic and electronic nature of these
structures using DFT. The study revealed strongly corrugated structures
for the fully polymerized g-C3N4 and planar structures for the incompletely polymerized g-C6N9H3. The exciton binding energies
of the heptazine-based structures are lower than that of their triazine-based
analogues and lower for the completely polymerized structures than
their incompletely polymerized analogues. The rather low dielectric
constant and charge mobilities result in high exciton binding energies
and hence low dissociation probabilities for these excitons. This
confirms the necessity of a morphology inspired by bulk heterojunction
architectures to ensure efficient charge carrier generation. The studied
compounds can be considered intermediates between typical inorganic
and organic semiconductors in terms of their photoabsorption properties.
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photoabsorption propertiesExciton Binding Energies3Npolymerized structuresdissociation probabilitiesCarbon Nitride Structurecrystal structurescharge carrier generationpolymerized analoguesheptazine monomers6Nbulk heterojunction architecturescharge mobilities resultDFT PerspectiveGraphiticexciton binding energiesphotocatalytic water splitting cells
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