| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系 === 107 === SUMMARY
The anomalous photovoltaic (PV) effect in BiFeO3 (BFO), which results in an open-circuit voltage that is considerably larger than the bandgap of the material, has recently received attention in the field of photoferroelectrics. For solar power applications, in addition to open-circuit voltage, electric current is important. In this study, we dope nickel into BFO to increase the carrier concentration and thus PV current. This doping is expected to increase the PV current by several-fold due to the introduction of extra carriers. Ni-doped BFO powder and epitaxy films are prepared via the hydrothermal method. The effects of nickel doping on the crystal structure, microstructure, chemical bonding, electrical resistance, and PV properties are investigated. The results show that BFO doped with 0-3% Ni has a perovskite structure. The addition of nickel effectively decreases the electrical resistance of BFO because it increases the oxygen vacancy concentration. The illumination current of Ni-doped BFO increases with increasing nickel content, which can be explained by the decrease in electrical resistance. The Ni-doped BFO films show rectifying characteristics similar to those of a diode. The current density-electric field behavior of the films differs from that of the bulk. The illumination current increases dramatically when the Ni-doped BFO films are illuminated.
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