Challenges in the ambient Raman spectroscopy characterization of methylammonium lead triiodide perovskite thin films

The importance of methylammonium lead triiodide (CH3NH3PbI3 or MAPbI(3)) organic-inorganic hybrid perovskites has shot up dramatically since their use in highly efficient thin-film perovskite solar cells (PSCs). However, the basic structural characterization of these fascinating materials remains sparse. In particular, Raman spectroscopy, which is a powerful vibrational spectroscopy characterization tool and complements other characterization methods, of MAPbI(3) under ambient conditions is plagued with difficulties. Here, a systematic ambient Raman spectroscopy characterization study of MAPbI(3) thin films is conducted under different conditions (excitation laser wavelength, integration time, filter characteristic). The results from this study help elucidate the possible sources of artifacts in the Raman spectra, and raise the awareness of the challenges in the ambient Raman spectroscopy of MAPbI(3) perovskites. Approaches to overcome these challenges are suggested.