Lead-free hybrid perovskite N(CH3)4SnI3 with robust ferroelectricity induced by large and non-polar N(CH3)4+ molecular cation

Hai Wei; Yali Yang; Shiyou Chen; H J Xiang

doi:10.1038/s41467-021-20889-y

Lead-free hybrid perovskite N(CH₃)₄SnI₃ with robust ferroelectricity induced by large and non-polar N(CH₃)₄⁺ molecular cation

Nat Commun. 2021 Jan 27;12(1):637. doi: 10.1038/s41467-021-20889-y.

Authors

Hai Wei^{1

2}, Yali Yang^{1

2}, Shiyou Chen³, H J Xiang^{4

5}

Affiliations

¹ Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China.
² Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China.
³ Key Laboratory of Polar Materials and Devices (Ministry of Education), East China Normal University, Shanghai, 200241, China. chensy@ee.ecnu.edu.cn.
⁴ Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai, 200433, China. hxiang@fudan.edu.cn.
⁵ Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, China. hxiang@fudan.edu.cn.

Abstract

The ferroelectricity in the hybrid perovskite CH₃NH₃PbI₃ is under debate because it results from the polar molecular cation CH₃NH₃⁺ while the molecular orientation was reported to be random. Here we predict that a Pb-free hybrid perovskite N(CH₃)₄SnI₃ with non-polar molecular cation N(CH₃)₄⁺ has strong ferroelectricity with a spontaneous polarization of 16.13 μC cm^-2. The large polarization results from the distortion of SnI₆ octahedron induced by the large N(CH₃)₄⁺ and is independent of the molecular orientation, so the ferroelectricity is robust. The ferroelectric R3m perovskite structure of N(CH₃)₄SnI₃ can be synthesized as the ground state under a hydrostatic pressure over 3 GPa and remains stable under ambient pressure. Given the strong ferroelectricity, good stability and high visible-light absorption, N(CH₃)₄SnI₃ may be an ideal light-absorber semiconductor for high-efficiency solar cells because its ferroelectric polarization can facilitate electron-hole separation and produce large bulk photovoltaic effect, making the design of homogeneous bulk photovoltaic devices possible.