Spectroscopic investigation of the solvated MAPbI3 transition to perovskite crystals: a temperature-dependent Raman study

Abstract

Hybrid organic–inorganic perovskites (HOIPs) have emerged as a transformative photovoltaic technology, achieving remarkable efficiency improvement in solar cell applications. However, the stability of perovskite-based materials remains a key issue and thus requires advanced non-destructive characterization methods. Raman spectroscopy, owing to its sensitivity to molecular and structural changes, is a promising tool for probing the surface characteristics of perovskite materials and for providing valuable insights into their vibrational properties and phase transition behavior. In this study, both in situ and ex situ Raman spectroscopy were employed to investigate the transition of solvated methylammonium iodide (MAI) and PbI₂ to MAPbI₃ perovskite crystals. The crystalline MAPbI₃ phase formed at 60 °C exhibited no distinct first-order Raman modes under 532 and 633 nm excitations, depicting its Raman inactivity under these conditions. Weak scattering features observed using a 785 nm laser can be attributed to the dynamic reorientation of methylammonium cations. These conclusions were supported by spectral measurements conducted under inert and atmospheric conditions at various power levels.