Enlarging photovoltaic effect: combination of classic photoelectric and ferroelectric photovoltaic effects

Abstract

Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm2) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials.

Effect of thickness on dielectric, ferroelectric, and optical properties of Ni substituted Pb(Zr0.2Ti0.8)O3 thin films

“…[1][2][3][4] The immense interest in optically active FE materials is due to the presence of strong spontaneous polarization which is necessary for ferroelectric photovoltaic currents, and control of photocurrents using the polarization direction. 5,6 Breaking of inversion symmetry in FE materials develops desirable separation of photo-excited charge carriers and produces photo-voltage higher than the bandgap.…”

“…5,6 Breaking of inversion symmetry in FE materials develops desirable separation of photo-excited charge carriers and produces photo-voltage higher than the bandgap. 1,3 Generally, metal/ferroelectric/metal device structures not only produce the photo-excited electron-hole pairs but also provide a polarization-induced internal electric field to separate the charge carriers. 3 In order to integrate ferroelectrics into suitable nanoscale devices, miniaturization is often necessary.…”

“…1,3 Generally, metal/ferroelectric/metal device structures not only produce the photo-excited electron-hole pairs but also provide a polarization-induced internal electric field to separate the charge carriers. 3 In order to integrate ferroelectrics into suitable nanoscale devices, miniaturization is often necessary. With the continued quest for ferroelectric photovoltaic (PV) applications, it is becoming increasingly important to scale the dimension of ferroelectrics down to the nanometer-scale size and thorough understanding of miniaturization effects on the material properties.…”

“…In general, ferroelectric materials are wide band gap insulators with low leakage currents. 1,3,7 The open circuit voltage (V oc ) of solar cell is typically limited by the bandgap of the material; hence, the tailoring of band gap of ferroelectric materials with doping of transition metal ions at B-site is a longstanding challenge. 4 Theoretically, it has been proposed that metallic defects, substitutions of transition metal ions can reduce the band gap of ferroelectric materials, which is a basic requirement for their applications as photovoltaic devices for complete solar spectrum.…”

“…[1][2][3][14][15][16] Yang et al 2 have shown that photovoltaic effect in BiFeO 3 (BFO) thin films which have relatively small band gaps (E g $2.6-2.9 eV) arises from a unique mechanism, namely, structurally driven steps of the electrostatic potential at nanometer-scale in-plane domains and domain a)…”