Significant THz-wave absorption property in mixed δ- and α-FAPbI3 hybrid perovskite flexible thin film formed by sequential vacuum evaporation.

The flexible and mixed δ- and α-formamidinium lead iodide (FAPbI₃) hybrid perovskite thin films fabricated by the sequential vacuum evaporation method (SVE) were studied using the THz-wave absorption property. The formed FAPbI₃ using SVE showed the typical δ-phase. After annealing for 10 min, we confirmed a mixed state with δ- and α-phases and observed THz-wave absorption at 1.62 THz with 40% absorptance. In the C 1s core-level spectra, we found two different chemical states originated from δ- and α-FAPbI₃. The origin of the THz-wave absorption property is assumed from a significant Pb–I vibration mode from the mixed phases in FAPbI₃. [ABSTRACT FROM AUTHOR]