Microscopic insight into the role of PVDF in improving the phototronic properties of a tin-derived perovskite in their nanocomposite

In this study, we investigated the possibility of nanocomposite formation between polyvinylidene fluoride (PVDF) and perovskite Cs₂SnF₃I₃ using density functional theory (DFT). The Gibbs free energy changes of about - 23 kcal/mol observed during the formation of the complexes indicates that this process is thermodynamically feasible. The NBO and AIM results also confirmed that the interactions of a physical nature at several points between PVDF and this perovskite cause this favorable interaction. The gap energy value of Cs₂SnF₃I₃ 3.629 eV and its composites were obtained 3.255 eV, which indicates that their optical excitation occurs at short wavelengths of light, namely near ultraviolet and violet-blue. The study of UV-vis spectra of this perovskite and its complexes with PVDF showed that the creation of composites, in addition to changing the wavelength of absorption peaks towards visible light, can also increase the absorption intensity. The polarity study also showed that due to the composite of Cs₂SnF₃I₃ with PVDF, its dipole moment increased from 10.28 to 14.71 Debye. In addition, the polarizability coefficient and the first hyperpolarizability coefficient also increased with the increase in the number of perovskite units in the composites, improving their optical properties.