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Abstract We report the pulsed‐laser deposition of epitaxial double‐perovskite Bi2FeCrO6(BFCO) films on the (001)‐, (110), and (111)‐oriented single‐crystal SrTiO3substrates. All of the BFCO films with various orientations show theandsuperlattice‐diffraction peaks. The intensity ratios between the‐superlattice and the main 111‐diffraction peak can be tailored by simply adjusting the laser repetition rate and substrate temperature, reaching up to 4.4%. However, both optical absorption spectra and magnetic measurements evidence that the strong superlattice peaks are not correlated with theB‐site Fe3+/Cr3+cation ordering. Instead, the epitaxial (111)‐oriented Bi2FeCrO6films show an enhanced remanent polarization of 92 μC/cm2at 10 K, much larger than the predicted values by density‐functional theory calculations. Positive‐up‐negative‐down (PUND) measurements with a time interval of 10 μs further support these observations. Therefore, our experimental results reveal that the strong superlattice peaks may come fromA‐ orB‐site cation shifts along the pseudo‐cubic [111] direction, which further enhance the ferroelectric polarization of the BFCO thin films.
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Photovoltaic Diode Effect Induced by Positive Bias Poling of Organic Layer‐Mediated Interface in Perovskite Heterostructure α‐HC(NH 2 ) 2 PbI 3 /TiO 2
It is shown that in the formamidinium (FA) lead iodide/titania heterostructure α‐HC(NH2)2PbI3/TiO2the organic layer‐mediated interface, i.e., FAI/TiO2, can induce photovoltaic diode effect via positive bias poling. The band gap of the heterostructure is reduced to zero upon the positive poling due to combined effects of ion diffusion, rotation of organic moieties, and ferroelectric redistribution. The perovskite part in the organic layer‐mediated interface FAI/TiO2gives rise to a strong polarization of 18.69 μC cm−2, compared to that (0.89 μC cm−2) in the inorganic layer‐mediated interface PbI2/TiO2. The strong polarization of the organic layer‐mediated interface is closely related to the diode effect associated with the reordering of the ferroelectric polarization and charge distribution, as a consequence of the mobility and rotation of organic moieties in FAI/TiO2upon the positive bias poling. The latter effect also provides an explanation on why the FAPbI3‐based devices can largely reduce the scanning hysteresis in theJ–Vcurves (Yang et al.,Science2015,348, 1234) and why the organic layer‐mediated halide perovskite heterostructure is one of the most promising candidates for the fabrication of highly efficient solar cells or optoelectronic devices.
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- Award ID(s):
- 1538893
- PAR ID:
- 10235557
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Interfaces
- Volume:
- 3
- Issue:
- 17
- ISSN:
- 2196-7350
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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