The interplay of bulk and interfacial dynamics in methylammonium lead triiodide perovskite solar cells revealed via current noise spectroscopy

Hybrid organic-inorganic perovskite solar cells are one of the most promising emerging technologies capable of competing with silicon devices, chief among them those based on methylammonium lead triiodide (MAPbI₃). Fundamental understanding of electrical transport and degradation processes in these devices, however, is important for commercial realization. We have performed cross-correlated current noise spectroscopy on a series of MAPbI₃ devices. Under illumination, we find near-full-scale shot noise (Fano factor F ~ 1), indicating the dominance of a single element in the device stack. We further observe generation-recombination noise which emerges with illumination and increasing device thickness. This signal is attributed to radiative bimolecular recombination. Finally, we observe a 1/f^a flicker noise (a ~ 1.4) which deviates from the expected I² dependence. This indicates the superposition of canonical resistance fluctuations and a current and/or light-driven source, likely the migration of halide ions through the bulk.