  Many optoelectronic properties have been reported for lead halide perovskite
polycrystalline films. However, ambiguities in the evaluation of these
properties remain, especially for long-range lateral charge transport, where
ionic conduction can complicate interpretation of data. Here we demonstrate a
new technique to measure the long-range charge carrier mobility in such
materials. We combine quasi-steady-state photo-conductivity measurements
(electrical probe) with photo-induced transmission and reflection measurements
(optical probe) to simultaneously evaluate the conductivity and charge carrier
density. With this knowledge we determine the lateral mobility to be ~ 2 cm2/Vs
for CH3NH3PbI3 (MAPbI3) polycrystalline perovskite films prepared from the
acetonitrile/methylamine solvent system. Furthermore, we present significant
differences in long-range charge carrier mobilities, from 2.2 to 0.2 cm2/Vs,
between films of contemporary perovskite compositions prepared via different
fabrication processes, including solution and vapour phase deposition
techniques. Arguably, our work provides the first accurate evaluation of the
long-range lateral charge carrier mobility in lead halide perovskite films,
with charge carrier density in the range typically achieved under photovoltaic
operation.
