Effect of HfO₂ on the dielectric, optoelectronic and energy harvesting properties of PVDF

In this article, energy recovery based on PVDF doped with HfO₂ is proposed. The free energy of CH₂=CF₂ is determined in different base with the B3LPY functional. The basis set LanL2DZ was chosen because it takes into account the atom of hafnium of atomic number \({\text{Z}} = 72\) which exceeds the extension of some basis sets. In addition, LanL2DZ gives an accurate result and a reasonable computing time. The geometries of the molecules were optimized with B3LPY/LanL2DZ. The motivation of this study is the improvement of the optoelectronic, dielectric and piezoelectric properties of PVDF by introducing HfO₂ into its matrix. We determined the parameters of \(\left( { {-} {\text{CH}}_{2} {-} {\text{CF}}_{2} {-} } \right)_{3} \cdot {\text{xHfO}}_{2}\) and identified the effect of HfO₂ on the PVDF. It appears that the permittivity of the modified PVDF increases. When the PVDF is doped once or twice, a fluorine atom is captured by the hafnium. The migration of fluorine towards HfO₂ considerably favors the electric polarization of the molecule. It then results in an important dipole moment with a polar phase undoubtedly favored. Our results show that the molecule \(\left( { {-} {\text{CH}}_{2} {-} {\text{CF}}_{2} {-} } \right)_{3} \cdot {\text{HfO}}_{2}\) is a good dielectric material (\({\text{E}}_{\text{g}} = 5.90\;{\text{eV}}\)) and can be a good piezoelectric material. The electronic affinity of the modified PVDF is significantly higher than that of virgin PVDF. This demonstrates that HfO₂-doped PVDF is more stable than virgin PVDF. The piezoelectric properties are significantly improved. The piezoelectric coefficient varies between 13.111 and 25.635 pC N⁻¹ for the modified PVDF compared to \(11.979\;{\text{pC N }}^{-1}\) for the virgin PVDF. In conclusion, HfO₂ improves the dielectric, optoelectronic and piezoelectric properties of PVDF.