Investigation of charge dynamics and photoinduced charge transfer in metal halide perovskite/carbon nanotube composites by vibrational spectroscopy*

Composites formed from metal halide perovskites and semiconducting carbon nanotubes show a fast photoinduced charge diffusion and a slow structural rearrangement due to ionic movement. To understand this latter, phonon-related mechanism, we performed a study of vibrational spectra on various perovskites and composites, changing the central ion of (Pb, Sn, Co and Cu) and the halide (I, Br and Cl). We measured the temperature dependence, followed the phase transitions, and investigated the photoinduced changes by both infrared and Raman spectroscopy. As the structural rearrangement is accompanied by Fermi level alignment and thus modifies the optical gap, our results are useful for fine-tuning the optical properties in solar cell applications of perovskites and perovskite/carbon nanostructure composites.