Large piezoelectric response in a Jahn-Teller distorted molecular metal halide

Area of Science:

• Materials Science
• Solid State Physics
• Energy Harvesting

Background:

• Piezoelectric materials convert mechanical to electrical energy, crucial for self-powered electronics.
• Existing piezoelectrics face a trade-off between charge (d33) and voltage (g33) coefficients, limiting maximum energy harvesting density (d33*g33).
• A key challenge is the simultaneous increase in polarization and dielectric constant, hindering optimal performance.

Purpose of the Study:

• To design and synthesize a piezoelectric material overcoming the d33-g33 trade-off.
• To achieve high energy conversion efficiency by maximizing the transduction coefficient (d33*g33).
• To develop a heavy-metal-free molecular piezoelectric for advanced energy harvesting applications.

Main Methods:

• Employed a design strategy to increase polarization via Jahn-Teller lattice distortion.
• Reduced dielectric constant using a confined 0D molecular architecture with a quasi-spherical cation.
• Synthesized and characterized EDABCO-CuCl4 (N-ethyl-1,4-diazoniabicyclo[2.2.2]octonium copper tetrachloride) as a molecular piezoelectric.

Main Results:

• Achieved a d33 coefficient of 165 pm/V and a g33 coefficient of ~2110 × 10^-3 V m N^-1.
• Obtained a combined transduction coefficient of 348 × 10^-12 m^3 J^-1.
• Demonstrated a peak power density of 43 µW/cm^2 in an EDABCO-CuCl4@PVDF composite film.

Conclusions:

• EDABCO-CuCl4 represents a significant advancement in molecular piezoelectric materials.
• The developed material enables highly efficient piezoelectric energy harvesting.
• This work sets a new benchmark for power density in heavy-metal-free molecular piezoelectric mechanical energy harvesters.