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Download filePersistent Quantum Coherence and Strong Coupling Enable Fast Electron Transfer across the CdS/TiO2 Interface: A Time-Domain ab Initio Simulation
journal contribution
posted on 2018-10-16, 00:00 authored by Hamid Mehdipour, Alexey V. Akimov, Joanna Jankowska, Ali T. Rezakhanai, Saeedeh S. Tafreshi, Nora H. de Leeuw, Alireza Z. Moshfegh, Oleg V. PrezhdoFast
transfer of photoinduced electrons and subsequent slow electron–hole
recombination in semiconductor heterostructures give rise to long-lived
charge separation which is highly desirable for photocatalysis and
photovoltaic applications. As a type II heterostructure, CdS/TiO2 nanocomposites extend the absorption edge of the light spectrum
to the visible range and demonstrate effective charge separation,
resulting in more efficient conversion of solar energy to chemical
energy. This improvement in performance is partly explained by the
fact that CdS/TiO2 is a type II semiconductor heterostructure
and CdS has a smaller energy band gap than UV-active TiO2. Ultrafast transient absorption measurements have revealed that
electrons generated in CdS by visible light can quickly transfer into
TiO2 before recombination takes place within CdS. Here,
using time-domain density functional theory and nonadiabatic molecular
dynamics simulations, we show how electronic subsystems of the CdS
and TiO2 semiconductors are coupled to their lattice vibrations
and coherently evolve, enabling effective transfer of photoinduced
electrons from CdS into TiO2. This very fast electron transfer,
and subsequent slow recombination of the transferred electrons with
the holes left in CdS, is verified experimentally through the proven
efficient performance of CdS/TiO2 heterostructures in photocatalysis
and photovoltaic applications.