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New high T(c) multiferroics KBiFe₂O₅ with narrow band gap and promising photovoltaic effect.

Zhang G, Wu H, Li G, Huang Q, Yang C, Huang F, Liao F, Lin J - Sci Rep (2013)

Bottom Line: Computational "materials genome" searches have predicted several exotic MO₆ FE with E(g) < 2.0 eV, all thus far unconfirmed because of synthesis difficulties.Here we report a new FE compound with MO₄ tetrahedral network, KBiFe₂O₅, which features narrow E(g) (1.6 eV), high Curie temperature (T(c) ~ 780 K) and robust magnetic and photoelectric activities.The high photovoltage (8.8 V) and photocurrent density (15 μA/cm²) were obtained, which is comparable to the reported BiFeO₃.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China.

ABSTRACT
Intrinsic polarization of ferroelectrics (FE) helps separate photon-generated charge carriers thus enhances photovoltaic effects. However, traditional FE with transition-metal cations (M) of d⁰ electron in MO₆ network typically has a band gap (E(g)) exceeding 3.0 eV. Although a smaller E(g) (2.6 eV) can be obtained in multiferroic BiFeO₃, the value is still too high for optimal solar energy applications. Computational "materials genome" searches have predicted several exotic MO₆ FE with E(g) < 2.0 eV, all thus far unconfirmed because of synthesis difficulties. Here we report a new FE compound with MO₄ tetrahedral network, KBiFe₂O₅, which features narrow E(g) (1.6 eV), high Curie temperature (T(c) ~ 780 K) and robust magnetic and photoelectric activities. The high photovoltage (8.8 V) and photocurrent density (15 μA/cm²) were obtained, which is comparable to the reported BiFeO₃. This finding may open a new avenue to discovering and designing optimal FE compounds for solar energy applications.

No MeSH data available.


Related in: MedlinePlus

Photoelectric Responses of KBiFe2O5.(a) J-V curves in the dark and under UV illumination at room temperature. Inset shows the measurement setup schematically. (b) Zero-voltage photocurrent density following on-off UV exposure. (c) Open-circuit photovoltaic voltage following on-off UV exposure. (d) Photocatalytic decoloration of methylene blue (MB) under visible light with (lower) and without (upper) KBiFe2O5 powders. Inset: color evolution of MB at corresponding irradiation time.
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f6: Photoelectric Responses of KBiFe2O5.(a) J-V curves in the dark and under UV illumination at room temperature. Inset shows the measurement setup schematically. (b) Zero-voltage photocurrent density following on-off UV exposure. (c) Open-circuit photovoltaic voltage following on-off UV exposure. (d) Photocatalytic decoloration of methylene blue (MB) under visible light with (lower) and without (upper) KBiFe2O5 powders. Inset: color evolution of MB at corresponding irradiation time.

Mentions: The photoelectric responses were measured at room temperature using a single crystal illuminated by a UV-light (4 mW/cm2, λ ~ 254 nm) (see insert in Fig. 6a and Supplementary Fig. S17). Current–voltage (I–V) characteristics of samples reveal strikingly photovoltaic behavior, which is indicative of the polar nature of the sample. At zero bias, no dark current was seen but there is a negative photocurrent, with a large zero-current voltage (corresponding to the open-circuit photovoltaic voltage, Voc) of 8.8 V (Fig. 6a). This indicates that charge carriers have a preferred direction presumably because of an internal-field bias. The observation of an open circuit voltage larger than Eg is a signature of photovoltaic effects in multi-domained FE410. This above band gap Voc provides a promising platform for harvesting solar energy to generate electricity. These results provided strong evidence for the presence of a FE bias in the crystal. To substantiate the above results and to eliminate any heating effect caused by sustained light illumination, on-off photocurrent at zero voltage and Voc at zero current were measured (Fig. 6b and 6c), which again confirmed the photoelectric effect. A steady Voc was obtained as large as 9.1 V, which is consistent with the I–V result. The photocurrent density ~15 μA/cm2 is comparable to the one (7.35 μA/cm2) reported for BiFeO312. Note that our photovoltaic effect was measured from one single crystal sample whose photovoltaic efficiency is considerably limited. Photocurrent is known to be sensitive to the illumination condition and device configuration43940, so a major enhancement in its value is possible by modifying these parameters and by tuning conductivity.


New high T(c) multiferroics KBiFe₂O₅ with narrow band gap and promising photovoltaic effect.

Zhang G, Wu H, Li G, Huang Q, Yang C, Huang F, Liao F, Lin J - Sci Rep (2013)

Photoelectric Responses of KBiFe2O5.(a) J-V curves in the dark and under UV illumination at room temperature. Inset shows the measurement setup schematically. (b) Zero-voltage photocurrent density following on-off UV exposure. (c) Open-circuit photovoltaic voltage following on-off UV exposure. (d) Photocatalytic decoloration of methylene blue (MB) under visible light with (lower) and without (upper) KBiFe2O5 powders. Inset: color evolution of MB at corresponding irradiation time.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569630&req=5

f6: Photoelectric Responses of KBiFe2O5.(a) J-V curves in the dark and under UV illumination at room temperature. Inset shows the measurement setup schematically. (b) Zero-voltage photocurrent density following on-off UV exposure. (c) Open-circuit photovoltaic voltage following on-off UV exposure. (d) Photocatalytic decoloration of methylene blue (MB) under visible light with (lower) and without (upper) KBiFe2O5 powders. Inset: color evolution of MB at corresponding irradiation time.
Mentions: The photoelectric responses were measured at room temperature using a single crystal illuminated by a UV-light (4 mW/cm2, λ ~ 254 nm) (see insert in Fig. 6a and Supplementary Fig. S17). Current–voltage (I–V) characteristics of samples reveal strikingly photovoltaic behavior, which is indicative of the polar nature of the sample. At zero bias, no dark current was seen but there is a negative photocurrent, with a large zero-current voltage (corresponding to the open-circuit photovoltaic voltage, Voc) of 8.8 V (Fig. 6a). This indicates that charge carriers have a preferred direction presumably because of an internal-field bias. The observation of an open circuit voltage larger than Eg is a signature of photovoltaic effects in multi-domained FE410. This above band gap Voc provides a promising platform for harvesting solar energy to generate electricity. These results provided strong evidence for the presence of a FE bias in the crystal. To substantiate the above results and to eliminate any heating effect caused by sustained light illumination, on-off photocurrent at zero voltage and Voc at zero current were measured (Fig. 6b and 6c), which again confirmed the photoelectric effect. A steady Voc was obtained as large as 9.1 V, which is consistent with the I–V result. The photocurrent density ~15 μA/cm2 is comparable to the one (7.35 μA/cm2) reported for BiFeO312. Note that our photovoltaic effect was measured from one single crystal sample whose photovoltaic efficiency is considerably limited. Photocurrent is known to be sensitive to the illumination condition and device configuration43940, so a major enhancement in its value is possible by modifying these parameters and by tuning conductivity.

Bottom Line: Computational "materials genome" searches have predicted several exotic MO₆ FE with E(g) < 2.0 eV, all thus far unconfirmed because of synthesis difficulties.Here we report a new FE compound with MO₄ tetrahedral network, KBiFe₂O₅, which features narrow E(g) (1.6 eV), high Curie temperature (T(c) ~ 780 K) and robust magnetic and photoelectric activities.The high photovoltage (8.8 V) and photocurrent density (15 μA/cm²) were obtained, which is comparable to the reported BiFeO₃.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China.

ABSTRACT
Intrinsic polarization of ferroelectrics (FE) helps separate photon-generated charge carriers thus enhances photovoltaic effects. However, traditional FE with transition-metal cations (M) of d⁰ electron in MO₆ network typically has a band gap (E(g)) exceeding 3.0 eV. Although a smaller E(g) (2.6 eV) can be obtained in multiferroic BiFeO₃, the value is still too high for optimal solar energy applications. Computational "materials genome" searches have predicted several exotic MO₆ FE with E(g) < 2.0 eV, all thus far unconfirmed because of synthesis difficulties. Here we report a new FE compound with MO₄ tetrahedral network, KBiFe₂O₅, which features narrow E(g) (1.6 eV), high Curie temperature (T(c) ~ 780 K) and robust magnetic and photoelectric activities. The high photovoltage (8.8 V) and photocurrent density (15 μA/cm²) were obtained, which is comparable to the reported BiFeO₃. This finding may open a new avenue to discovering and designing optimal FE compounds for solar energy applications.

No MeSH data available.


Related in: MedlinePlus