Photovoltaic effects in BiFeO3

Abstract

We report a photovoltaic effect in ferroelectric BiFeO3 thin films. The all-oxide heterostructures with SrRuO3 bottom and tin doped indium oxide top electrodes are characterized by open-circuit voltages ∼0.8–0.9 V and external quantum efficiencies up to ∼10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the maximum efficiency under sunlight (AM 1.5) thus far reported for ferroelectric-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelectric polarization and band offsets at the BiFeO3/tin doped indium oxide interface.

Single ferroelectric-domain photovoltaic switch based on lateral BiFeO3 cells

“…Second, as shown in the upper left insets of Figures 1c and d, these features commonly exhibit a photovoltaic effect in the low-E-field region, consistent with the literature. [3][4][5][6][7][8] Figures 2a and d show the in-plane domain images and the corresponding I sc images for single-domain switching. In the intermediate reversal field, as in the domain image of E poling at þ 45 V and the I sc image at À20 V, the domain breaks up into two subdomains, showing signs of I sc to each other.…”

“…This phenomenon has been recently revisited with a small band-gap, BiFeO 3 (BFO) ferroelectric, from which a substantially higher photon-to-charge generation efficiency can be achieved in the visible range compared with that of other insulating ferroelectrics. [3][4][5][6][7][8] reported that diodelike rectification follows the polarization-dependent interface bandbending of BFO single-crystal slabs that are electrically switchable, that is, V oc and I sc are defined by the remanent polarization directions. In general, the spatial extent of spontaneous polarization vectors in ferroelectric crystals is typically manifested as domains (typically spanning over a few mm in size) and domain walls (DW, 1-2 nm in…”

Photoexcitation of gigahertz longitudinal and shear acoustic waves in BiFeO3 multiferroic single crystal

“…12,13 The mechanisms behind these properties are not fully understood yet as some traps arising from defects or Schottky barriers at electrode interface can affect the experimental observations. 10,13 Nevertheless, it is believed that light excitation allows injection of photocarriers whose motion is driven by the built-in electric field linked to the large polarization of BFO. As a matter of fact and in addition to magnetic and/or electric field, light appears as a powerful tool to probe and tune BFO multiferroic properties as well as an original way for the discovery of unrevealed yet phenomena.…”

Applications of ferroelectrics in photovoltaic devices

“…In silicon p-n junctions, the voltage associated with a 1-μm-thick depletion layer is 0.7 V; thus, the internal electric field is 0.7 kV mm −1 [15]. In the BFO thin films, the potential difference between the domains for a typical domain wall thickness of 2 nm is 10 mV; thus, the internal electric field is 5 kV mm −1 [14].…”

“…At the same time, Yang et al [14,15] reported a unique phenomenon-the photovoltaic characteristic of a singledomain-structure BFO thin film did not increase significantly with varying the film thickness. In a subsequent study, the authors prepared single-crystal BFO films and revealed a charge separation mechanism dramatically different from the traditional ones.…”