Ferroelectricity in a semiconducting all-inorganic halide perovskite

Ye Zhang; Eric Parsonnet; Abel Fernandez; Sinéad M Griffin; Huaixun Huyan; Chung-Kuan Lin; Teng Lei; Jianbo Jin; Edward S Barnard; Archana Raja; Piush Behera; Xiaoqing Pan; Ramamoorthy Ramesh; Peidong Yang

doi:10.1126/sciadv.abj5881

Ferroelectricity in a semiconducting all-inorganic halide perovskite

Sci Adv. 2022 Feb 11;8(6):eabj5881. doi: 10.1126/sciadv.abj5881. Epub 2022 Feb 9.

Authors

Ye Zhang¹, Eric Parsonnet², Abel Fernandez³, Sinéad M Griffin^{4

5}, Huaixun Huyan⁶, Chung-Kuan Lin^{1

4}, Teng Lei¹, Jianbo Jin¹, Edward S Barnard⁵, Archana Raja⁵, Piush Behera^{3

4}, Xiaoqing Pan^{6

7

8}, Ramamoorthy Ramesh^{2

3

4}, Peidong Yang^{1

3

4

9}

Affiliations

¹ Department of Chemistry, University of California, Berkeley, CA 94720, USA.
² Department of Physics, University of California, Berkeley, CA 94720, USA.
³ Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA.
⁴ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁵ Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁶ Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 92697, USA.
⁷ Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697, USA.
⁸ Irvine Materials Research Institute, University of California, Irvine, Irvine, CA 92697, USA.
⁹ Kavli Energy NanoScience Institute, Berkeley, CA 94720, USA.

Abstract

Ferroelectric semiconductors are rare materials with both spontaneous polarizations and visible light absorptions that are promising for designing functional photoferroelectrics, such as optical switches and ferroelectric photovoltaics. The emerging halide perovskites with remarkable semiconducting properties also have the potential of being ferroelectric, yet the evidence of robust ferroelectricity in the typical three-dimensional hybrid halide perovskites has been elusive. Here, we report on the investigation of ferroelectricity in all-inorganic halide perovskites, CsGeX₃, with bandgaps of 1.6 to 3.3 eV. Their ferroelectricity originates from the lone pair stereochemical activity in Ge (II) that promotes the ion displacement. This gives rise to their spontaneous polarizations of ~10 to 20 μC/cm², evidenced by both ab initio calculations and key experiments including atomic-level ionic displacement vector mapping and ferroelectric hysteresis loop measurement. Furthermore, characteristic ferroelectric domain patterns on the well-defined CsGeBr₃ nanoplates are imaged with both piezo-response force microscopy and nonlinear optical microscopic method.