Longitudinal Optical Phonons Modified by Organic Molecular Cation Motions in Organic-Inorganic Hybrid Perovskites.

We performed terahertz time-domain spectroscopy for methylammonium (MA) lead halide perovskite single crystals and characterized the longitudinal optical (LO) phonons directly. We found that the effective LO phonon wave number does not change in the wide temperature range between 10 and 300 K. However, the coupling between MA cation modes and the LO phonon mode derived from lead halide cages induces a mode splitting at low temperatures and a damping of the LO phonon mode at high temperatures.

Impact of Chemical Doping on Optical Responses in Bismuth-Doped CHNHPbBr Single Crystals: Carrier Lifetime and Photon Recycling.

We studied the optical responses of organic-inorganic halide perovskite CHNHPbBr single crystals doped with heterovalent Bi ions (electron densities up to 2.3 × 10 cm). The Bi doping causes no significant changes in the band gap energy but leads to an enhanced Urbach tail and photoluminescence blue shift.