Spectroscopic ellipsometry studies of CH3NH3PbX3 thin films and their growth evolution

CH
₃
NH
₃
PbX
₃
(X=I, Cl) perovskite films of interest for photovoltaics (PV) devices have been deposited by (i) evaporation followed by vapor annealing and (ii) co-evaporation. Near infrared to ultraviolet spectroscopic ellipsometry has been used to determine the spectroscopic optical response for vapor-annealed material ex situ and co-evaporated material in situ during growth. Real time spectroscopic ellipsometry (RTSE) applied during co-evaporation has tracked the formation and time evolution of perovskite and phase segregated layers at the substrate and surface interfaces. Good agreement between density functional theory (DFT) calculations of optical response and experimental measurements has also been demonstrated.