  Using cross-correlation current noise spectroscopy, we have investigated
carrier dynamics in methylammonium lead triiodide solar cells. This method
provides a space selectivity for devices with planar multi-layered structure,
effectively amplifying current noise contributions coming from the most
resistive element of the stack. In the studied solar cells, we observe near
full-scale shot noise, indicating the dominance of noise generation by a single
source, likely the interface between the perovskite and the spiro-OMeTAD
hole-transport layer. We argue that the strong 1/f noise term has contributions
both from the perovskite layer and interfaces. It displays non-ideal dependence
on photocurrent, $S \propto I^{1.4}$ (instead of usual $S \propto I^2$ ), which
is likely due to current-induced halide migration. Finally, we observe
generation-recombination noise. The relaxation time of this process grows
linearly with photocurrent, which allows to attribute this contribution to
bimolecular recombination in the perovskite bulk absorption layer.
Extrapolating our results, we estimate that at the standard 1 sun illumination
the electron-hole recombination time is 5 microseconds.
