We found new phonon vibration modes in formamidinium (FA)-based hybrid perovskite structures. We intriguingly found that the δ/α-mixed-phase exhibited significant THz-wave absorption peaks at 2.0 and 2.2 THz that were not related to any phonon modes from either the δ- or α-phases, although the δ/α-mixed-phase sample was confirmed to be formed by a physical combination of the δ- and α-phases without the creation of any new chemical states. From the theoretical study, they originate from the novel vibration modes excited at the seamless interfaces in the mixed phase of FAPbI3.
- Inhee Maeng
- Seungjun Lee
- Min-Cherl Jung