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

In this article, energy recovery based on PVDF doped with HfO is proposed. The free energy of CH=CF 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 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 HfO into its matrix. We determined the parameters of (-CH2-CF2-)3·xHfO2 and identified the effect of HfO 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 HfO 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 (-CH2-CF2-)3·HfO2 is a good dielectric material (Eg=5.90eV) 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 HfO-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 for the modified PVDF compared to 11.979pC N-1 for the virgin PVDF. In conclusion, HfO improves the dielectric, optoelectronic and piezoelectric properties of PVDF.