jp8b11554_si_001.pdf (1.35 MB)
Band-Edge Engineering at the Carbon Dot–TiO2 Interface by Substitutional Boron Doping
journal contribution
posted on 2019-02-19, 00:00 authored by Dipayan Sen, Piotr Błoński, Michal OtyepkaWe
investigated the heterostructures of pristine and boron-doped
carbon dots (CDs) with TiO2 using a first principles approach.
Heterojunctions of CDs and TiO2 demonstrated type II band
alignments that promote spatial separation of charge carriers and
were well suited for sensitizer configuration. However, large CD band
gaps severely restricted their optical efficiencies. Substitutional
boron doping of the CDs introduced new electronic states and pulled
the CDs’ conduction band minimum (CBM) down, resulting in dramatic
reduction of CD band gaps (by 48–57%). The resulting band alignment
of the boron-doped CD–TiO2 heterostructures were
found to be type I, in which CBM and valence band maximum of TiO2 straddled those of CDs and photoexcited carriers could migrate
to CD side. This indicated better suitability for device configurations
where conducting channel lies through the CDs but elevated the chance
of recombination loss. However, the internal electric fields at these
heterojunctions were found to selectively promote electron migration
and hinder hole migration, which we postulate could counter the recombination
loss in these systems. The obtained results offer insights into designing
a new generation of water-splitting photocatalysts that would be able
to utilize a broader spectrum of solar radiation than the current
solutions.