We demonstrate that
halide content strongly affects nonradiative
electron–hole recombination in all-inorganic perovskite quantum
dots (QDs). Using time domain density functional theory and nonadiabatic
molecular dynamics, we show that replacing half of the bromines with
iodines in a CsPbBr3 QD extends the charge carrier lifetime
by a factor of 5, while complete replacement extends the lifetime
by a factor of 8. Doping with iodines decreases the nonadiabatic charge–phonon
coupling because iodines are heavier and slower than bromines and
because the overlap between the electron and hole wave functions is
reduced. In general, the nonradiative electron–hole recombination
proceeds slowly, on a nanosecond time scale, due to small sub-1 meV
nonadiabatic coupling and short sub-10 fs coherence times. The obtained
recombination times and their dependence on the halogen content show
excellent agreement with experiments. Our study suggests that the
power conversion efficiencies of solar cells can be controlled by
changing the halide composition in all-inorganic perovskite QDs.
We investigate superconductor/insulator/ferromagnet/superconductor tunnel Josephson junctions in the dirty limit using the quasiclassical theory. We formulate a quantitative model describing the oscillations of critical current as a function of thickness of the ferromagnetic layer and use this model to fit recent experimental data. We also calculate quantitatively the density of states ͑DOS͒ in this type of junctions and compare DOS oscillations with those of the critical current.
An attractive two-dimensional semiconductor with tunable direct bandgap and high carrier mobility, black phosphorus (BP), is used in batteries, solar cells, photocatalysis, plasmonics, and optoelectronics. BP is sensitive to ambient conditions, with oxygen playing a critical role in structure degradation. Our simulations show that BP oxidation slows down charge recombination. This is unexpected, since typically charges are trapped and lost on defects. First, BP has no ionic character. It interacts with oxygen and water weakly, experiencing little perturbation to electronic structure. Second, phosphorus supports different oxidation states and binds extraneous atoms avoiding deep defect levels. Third, soft BP structure can accommodate foreign species without disrupting periodic geometry. Finally, BP phonon scattering on defects shortens quantum coherence and suppresses recombination. Thus, oxidation can be regarded as production of a self-protective layer that improves BP properties. These BP features should be common to other monoelemental 2D materials, stimulating energy and electronics applications.
Atomistic details govern quantum dynamics of charge carriers in metal halide perovskites, which exhibit properties of solid state and molecular semiconductors, as revealed by time-domain density functional theory and nonadiabatic molecular dynamics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.