Abstract
Metal-free organic perovskite ferroelectric materials have been shown recently to have a number of attractive properties, including high spontaneous polarization and piezoelectric coefficients. In particular, slow evaporation of solutions containing organic amines, inorganic ammoniums, and dilute hydrohalogen acid has been shown to produce several attractive materials in the MDABCO-NH4-I3 family (MDABCO is N-methyl-N’-diazabicyclo[2,2,2] octonium). In the present work, we study by first-principles calculations the origin of polarizaiton, electronic density of state, piezoelectric response, and elastic properties of MDABCO-NH4-X3 (X = Cl, Br, I). We find that the dipole moments of the MDABCO and NH4 groups are negligible, and the large spontaneous polarization of MDABCO-NH4-I3 mainly results from MDABCO and NH4 being off-center relative to I ions. Although the piezoelectric response of organic materials is usually very weak, we observe large piezoelectric strain components, dx4 and dx5; the calculated dx5 is 119 pC/N for MDABCO-NH4-Cl3, 248 pC/N for MDABCO-NH4-Br3 and 178 pC/N for MDABCO-NH4-I3. The large value of dx5 is found to be closely related with the large value of elastic compliance tensor, s44. These results show that MDABCO-NH4-X3 metal-free organic perovskites have large piezoelectric response with soft elastic properties.
Highlights
The perovskite structures have been dubbed a “chameleon” due to their rich diversity of chemical compositions and physical properties.[1,2,3] Searching for large piezoelectric perovskites has been the aspiration of science and engineering studies.[4]
NH4-I3 crystal is composed of three building blocks: NH4, MDABCO, and I6 octahedron
The MDABCO locates in the middle of a cage defined by 12 iodine ions
Summary
The perovskite structures have been dubbed a “chameleon” due to their rich diversity of chemical compositions and physical properties.[1,2,3] Searching for large piezoelectric perovskites has been the aspiration of science and engineering studies.[4]. A breakthrough of piezoelectric material was reported by Yu-Meng You, Ren-Gen Xiong, and colleagues.[9] Based on molecular design strategy and elaborate organic cation selection, they successfully synthesized a family of metal-free organic perovskite ferroelectrics. This family contains 23 new compounds, in which 21 compounds have cubic perovskite structure and the other two have hexagonal perovskite structure. The facile synthesis method and their desirable properties make them are possible for application in flexible devices Among this metal-free organic perovskite family, MDABCO-NH4I3 (MDABCO is N-methyl-N’-diazabicyclo[2,2,2]octonium) is an outstanding one. The elastic tensor and piezoelectric strain tensor were not reported, too
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
