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Wide-bandgap molecular ferroelectric with thermally switchable dielectric and NLO responses from non-chiral design.

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Title: Wide-bandgap molecular ferroelectric with thermally switchable dielectric and NLO responses from non-chiral design.
Authors: Li, Duo-Fu1 (AUTHOR), Chen, Jia-Wei1 (AUTHOR), Lin, Shu-Han1 (AUTHOR), Chen, Cheng1 (AUTHOR), Zhao, Hai-Bing1 (AUTHOR), Sui, Yan1 (AUTHOR) suiyan@jgsu.edu.cn
Source: Journal of Molecular Structure. Feb2026:Part 1, Vol. 1351, pN.PAG-N.PAG. 1p.
Subjects: Optoelectronics, Band gaps, Thermal stability, Hard materials, Nonlinear optical techniques, Ferroelectric transitions, Ferroelectric crystals
Abstract: • Chiral-free ferroelectric with P ₛ = 17.57 μC/cm², avoiding costly chiral precursors. • Reversible dielectric/NLO switching at 352 K (ε′: 5→10, SHG: 0.5 × KDP→0). • Wide bandgap (4.73 eV) enables high transparency and "absorption-free" SHG. • Thermally stable (>480 K) with robust cycling for optoelectronic applications. Molecular ferroelectrics that combine switchable dielectric and nonlinear optical (NLO) properties hold great promise for next-generation flexible and wearable optoelectronic devices. However, their development is often hindered by the reliance on expensive chiral precursors and limited thin-film processability. In this study, we report the rational design of a flexible organic molecular ferroelectric, chloroethyltrimethylammonium fluoroborate ([CETMA][BF₄]), using low-cost non-chiral precursors and a fluoroborate anion strategy. This compound features a wide bandgap of 4.73 eV and undergoes a thermally reversible first-order phase transition at 352 K (ΔS = 21.83 J mol⁻¹ K⁻¹), enabling dual switching of both dielectric and NLO responses. The transition involves symmetry breaking between the polar phase Cmc 2₁ (SHG response: 0.5×KDP; dielectric constant ε′ = 5) and the centrosymmetric phase P 6₃/ mmc (SHG: 0; ε′ = 10), accompanied by broad optical transparency across the 300–2500 nm range. The material exhibits a notable spontaneous polarization (P ₛ) of 17.57 μC/cm² and demonstrates a superior combination of wide bandgap and high transparency, outperforming many classical ferroelectric materials. This work provides a feasible design strategy for developing high-performance metal-free ferroelectrics with enhanced integrability and functionality for modern optoelectronic applications. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:• Chiral-free ferroelectric with P ₛ = 17.57 μC/cm², avoiding costly chiral precursors. • Reversible dielectric/NLO switching at 352 K (ε′: 5→10, SHG: 0.5 × KDP→0). • Wide bandgap (4.73 eV) enables high transparency and "absorption-free" SHG. • Thermally stable (>480 K) with robust cycling for optoelectronic applications. Molecular ferroelectrics that combine switchable dielectric and nonlinear optical (NLO) properties hold great promise for next-generation flexible and wearable optoelectronic devices. However, their development is often hindered by the reliance on expensive chiral precursors and limited thin-film processability. In this study, we report the rational design of a flexible organic molecular ferroelectric, chloroethyltrimethylammonium fluoroborate ([CETMA][BF₄]), using low-cost non-chiral precursors and a fluoroborate anion strategy. This compound features a wide bandgap of 4.73 eV and undergoes a thermally reversible first-order phase transition at 352 K (ΔS = 21.83 J mol⁻¹ K⁻¹), enabling dual switching of both dielectric and NLO responses. The transition involves symmetry breaking between the polar phase Cmc 2₁ (SHG response: 0.5×KDP; dielectric constant ε′ = 5) and the centrosymmetric phase P 6₃/ mmc (SHG: 0; ε′ = 10), accompanied by broad optical transparency across the 300–2500 nm range. The material exhibits a notable spontaneous polarization (P ₛ) of 17.57 μC/cm² and demonstrates a superior combination of wide bandgap and high transparency, outperforming many classical ferroelectric materials. This work provides a feasible design strategy for developing high-performance metal-free ferroelectrics with enhanced integrability and functionality for modern optoelectronic applications. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:00222860
DOI:10.1016/j.molstruc.2025.144233