%0 Journal Article
%K Electronics
%K Light absorption
%K Electric potential
%K Semiconductor
%K Electric fields
%K Iron compounds
%K Domain walls
%K Ferroelectric materials
%K Bismuth compounds
%K Energy conversion
%K Energy gap
%K Ferroelectricity
%K Electric field
%K Article
%K Priority journal
%K Ferroelectric domains
%K Electric-field control
%K Electrostatic potentials
%K Semiconductor electronics
%K Semiconductor devices
%K Photovoltaic effects
%K Photovoltaic devices
%K Solid state
%K Nanomaterial
%K Optoelectronic devices
%K Charge separations
%K Different mechanisms
%K Electron hole pairs
%K Photovoltaic device
%A S.Y Yang
%A J Seidel
%A S.J Byrnes
%A P Shafer
%A C.-H Yang
%A M.D Rossell
%A P Yu
%A Y.-H Chu
%A J.F Scott
%A Joel W Ager
%A L.W Martin
%A Ramamoorthy Ramesh
%B Nature Nanotechnology
%D 2010
%G eng
%I Nature Publishing Group
%P 143-147
%R 10.1038/nnano.2009.451
%T Above-bandgap voltages from ferroelectric photovoltaic devices
%V 5
%X In conventional solid-state photovoltaics, electron-hole pairs are created by light absorption in a semiconductor and separated by the electric field spaning a micrometre-thick depletion region. The maximum voltage these devices can produce is equal to the semiconductor electronic bandgap. Here, we report the discovery of a fundamentally different mechanism for photovoltaic charge separation, which operates over a distance of 1-2nm and produces voltages that are significantly higher than the bandgap. The separation happens at previously unobserved nanoscale steps of the electrostatic potential that naturally occur at ferroelectric domain walls in the complex oxide BiFeO 3. Electric-field control over domain structure allows the photovoltaic effect to be reversed in polarity or turned off. This new degree of control, and the high voltages produced, may find application in optoelectronic devices. © 2010 Macmillan Publishers Limited. All rights reserved.