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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

Band structure of KBiFe2O5.(a) UV-Vis-near IR absorption spectrum of KBiFe2O5. Inset: (αhv)2 versus hv for band gap determination. (b) Band structure of KBiFe2O5, (c) Spin-up (left branch) and spin-down (right branch) components of density of states (DOS), and (d) charge density parallel to the 001 plane.
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f5: Band structure of KBiFe2O5.(a) UV-Vis-near IR absorption spectrum of KBiFe2O5. Inset: (αhv)2 versus hv for band gap determination. (b) Band structure of KBiFe2O5, (c) Spin-up (left branch) and spin-down (right branch) components of density of states (DOS), and (d) charge density parallel to the 001 plane.

Mentions: Our expectation of a smaller Eg and a higher conductivity for tetrahedral compounds was supported by optical absorption spectrum (Fig. 5a) which shows increased absorption starting at 750 nm. Using the plot of photon energy hv versus (αhv)2 (α for absorbance), we extrapolated an absorption edge of 1.59 eV which corresponds to the optical band gap (Fig. 5a inset). This value is considerably lower than that of BiFeO3 and is near the optimal band gap (1.50 eV) for solar energy applications. The smaller Eg is consistent with a lower resistance: the room-temperature resistance of the single sample obtained from the dark Current-voltage measurement discussed later is about 0.96 × 107 Ω·cm, which is three orders of magnitude lower than that of BiFeO3. Moreover, the large light absorption coefficient of the sample was detected as > 104 cm−1 (Supplementary Fig. S16), which is suitable for solar energy application.


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)

Band structure of KBiFe2O5.(a) UV-Vis-near IR absorption spectrum of KBiFe2O5. Inset: (αhv)2 versus hv for band gap determination. (b) Band structure of KBiFe2O5, (c) Spin-up (left branch) and spin-down (right branch) components of density of states (DOS), and (d) charge density parallel to the 001 plane.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Band structure of KBiFe2O5.(a) UV-Vis-near IR absorption spectrum of KBiFe2O5. Inset: (αhv)2 versus hv for band gap determination. (b) Band structure of KBiFe2O5, (c) Spin-up (left branch) and spin-down (right branch) components of density of states (DOS), and (d) charge density parallel to the 001 plane.
Mentions: Our expectation of a smaller Eg and a higher conductivity for tetrahedral compounds was supported by optical absorption spectrum (Fig. 5a) which shows increased absorption starting at 750 nm. Using the plot of photon energy hv versus (αhv)2 (α for absorbance), we extrapolated an absorption edge of 1.59 eV which corresponds to the optical band gap (Fig. 5a inset). This value is considerably lower than that of BiFeO3 and is near the optimal band gap (1.50 eV) for solar energy applications. The smaller Eg is consistent with a lower resistance: the room-temperature resistance of the single sample obtained from the dark Current-voltage measurement discussed later is about 0.96 × 107 Ω·cm, which is three orders of magnitude lower than that of BiFeO3. Moreover, the large light absorption coefficient of the sample was detected as > 104 cm−1 (Supplementary Fig. S16), which is suitable for solar energy application.

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