Abstract
Spontaneous polarization is shown to enhance the lifetimes of photogenerated species in BaTiO3 . This is attributed to polarization-induced surface band bending acting as a thermal barrier to electron/hole recombination. The study indicates that the efficiencies of solar cells and solar fuels devices can be enhanced by the use of ferroelectric materials.
Highlights
Band bending associated with the spontaneous polarization of a ferroelectric material, has the potential to substantially impact on the charge carrier lifetimes, and the efficiency, of solar energy conversion devices
Ferroelectric domainspecific redox reactions have been reported to occur on the surfaces of BaTiO3, Pb(Zr,Ti)O3, and LiNbO3 substrates,[19,20,21] indicating that the dipole drives electrons and holes to opposite surfaces determined by the direction of the spontaneous polarization and resultant band bending
We test the hypothesis that the presence of spontaneous polarization-induced band bending can result in increased charge carrier lifetimes
Summary
We turn to the likely impact of this temperature dependent band bending on charge carrier recombination. Such band bending can be expected to result in a thermal barrier Eb to charge recombination, as illustrated, with the recombination time constant expected to show an exponential dependence upon the barrier height. We assume Eb is decreasing approximately linearly with increasing temperature between 30 and 100 °C such that, Eb(T ) = Eb (30 °C) − ΔEb(T − 30)/70 where ΔEb is the reduction in Eb between 30 and 100 °C Applying this temperature dependent barrier energy to an Arrhenius type activation energy analysis, we obtain an effective activation energy. In the presence of a linearly decreasing thermal barrier to charge recombination, we still expect Arrhenius type behavior, but with an increased apparent activation energy
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