Mechanism for the high voltage photovoltaic effect in ceramic ferroelectrics

Photovoltaic effects in BiFeO3

“…The photovoltaic properties of ferroelectric oxide ceramics were originally investigated over 30 years ago in numerous materials including LiNbO 3 , [4][5][6] BaTiO 3 ͑BTO͒, 4 and Pb͑Zr, Ti͒O 3 ͑PZT͒. 7 Much excitement was generated due to the anomalously large open circuit photovoltages, in some cases Ͼ10 4 V, that were produced when the crystals were subject to illumination. It was concluded that the photovoltaic effect was a consequence of the noncentrosymmetry of the unit cell, which gives rise to asymmetries in electron excitation, relaxation, and scattering processes.…”

“…It was concluded that the photovoltaic effect was a consequence of the noncentrosymmetry of the unit cell, which gives rise to asymmetries in electron excitation, relaxation, and scattering processes. [4][5][6][7] The photovoltaic efficiencies, however, were limited by small current densities ͑on the order of 10 −9 A / cm 2 ͒ and the large band gaps ͑typically ϳ3.5 eV͒ of these materials.…”

Photoconductivity and photo-detection response of multiferroic bismuth iron oxide

“…21,28 In polycrystalline ferroelectric films/ceramics, photo current has been characterized to series connections of different grains/grain boundaries or domains/ domain walls. 29 The conducting domain walls become more semiconducting or insulating with increase in temperature which may reduce the charge generation near the interface. Figure 5 shows the temperature dependent behavior of dark and light current for two different stress voltages (42 and 98 V).…”

Applications of ferroelectrics in photovoltaic devices

“…In the open-circuit state, the crystal will yield a relatively high voltage. This voltage can be 2-4 orders of magnitude higher than the band gap (Eg) of the crystal [7]. In addition, one study found that the generated voltage is proportional to the thickness of the crystal in the direction of measurement, which is therefore considered a bulk effect.…”

“…In traditional silicon thin-film photovoltaic devices, electron-hole pairs are separated mainly by interfacial effects [7], such as the p-n junction, heterojunction, and Schottky barrier [17,18]. Devices with junction field structure need not only significantly different materials to yield a sufficiently strong electric field, but also good contact between these materials, which is a key factor determining their performance.…”