title: New high T(c) multiferroics KBiFe₂O₅ with narrow band gap and promising photovoltaic effect.
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.
authors: State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China.
authors: Ganghua
authors: G
authors: Zhang
authors: Hui
authors: H
authors: Wu
authors: Guobao
authors: G
authors: Li
authors: Qingzhen
authors: Q
authors: Huang
authors: Chongyin
authors: C
authors: Yang
authors: Fuqiang
authors: F
authors: Huang
authors: Fuhui
authors: F
authors: Liao
authors: Jianhua
authors: J
authors: Lin