Variation of Carrier Mobility in Metal-Halide Perovskite Thin Films with Stoichiometry

Carrier mobility and frequency-dependent conductivity measurements probe the quality of photoconductive thin films. We use ultrafast THz spectroscopy to measure carrier mobilities in lead-halide perovskite films produced by vapor phase deposition and spin coating. Initial results show a strong dependence of carrier mobility on film stoichiometry. A subset of samples also show suppressed conductivity at frequencies below 1THz suggesting partial carrier localization. Our optical pump/THz probe measurements determine effective mobilities from the ratio of light-induced change in conductivity to absorbed photon flux. Film stoichiometry was determined from IR and THz spectroscopy and X-Ray diffraction measurements. AFM was used to probe film structure. The authors acknowledge technical support from Prof. Aaron Massari, Dept. Chemistry, University of Minnesota.