Multidirection Piezoelectricity in Mono- and Multilayered Hexagonal α-In2Se3

Fei Xue, Junwei Zhang, Weijin Hu, Wei Ting Hsu, Ali Han, Siu Fung Leung, Jing Kai Huang, Yi Wan, Shuhai Liu, Junli Zhang, Jr Hau He, Wen-Hao Chang, Zhong Lin Wang, Xixiang Zhang*, Lain Jong Li

*Corresponding author for this work

Research output: Contribution to journalArticle

45 Scopus citations


Piezoelectric materials have been widely used for sensors, actuators, electronics, and energy conversion. Two-dimensional (2D) ultrathin semiconductors, such as monolayer h-BN and MoS2 with their atom-level geometry, are currently emerging as new and attractive members of the piezoelectric family. However, their piezoelectric polarization is commonly limited to the in-plane direction of odd-number ultrathin layers, largely restricting their application in integrated nanoelectromechanical systems. Recently, theoretical calculations have predicted the existence of out-of-plane and in-plane piezoelectricity in monolayer α-In2Se3. Here, we experimentally report the coexistence of out-of-plane and in-plane piezoelectricity in monolayer to bulk α-In2Se3, attributed to their noncentrosymmetry originating from the hexagonal stacking. Specifically, the corresponding d33 piezoelectric coefficient of α-In2Se3 increases from 0.34 pm/V (monolayer) to 5.6 pm/V (bulk) without any odd-even effect. In addition, we also demonstrate a type of α-In2Se3-based flexible piezoelectric nanogenerator as an energy-harvesting cell and electronic skin. The out-of-plane and in-plane piezoelectricity in α-In2Se3 flakes offers an opportunity to enable both directional and nondirectional piezoelectric devices to be applicable for self-powered systems and adaptive and strain-tunable electronics/optoelectronics.

Original languageEnglish
Pages (from-to)4976-4983
Number of pages8
JournalACS Nano
Issue number5
StatePublished - 22 May 2018


  • monolayer and bulk
  • multidirection
  • nanogenerator and electronic skin
  • piezoelectricity
  • van der Waals crystal

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    Xue, F., Zhang, J., Hu, W., Hsu, W. T., Han, A., Leung, S. F., Huang, J. K., Wan, Y., Liu, S., Zhang, J., He, J. H., Chang, W-H., Wang, Z. L., Zhang, X., & Li, L. J. (2018). Multidirection Piezoelectricity in Mono- and Multilayered Hexagonal α-In2Se3. ACS Nano, 12(5), 4976-4983.