Are Mobilities in Hybrid Organic−Inorganic Halide Perovskites

Actually “High”? T outstanding performance of hybrid organic−inorganic perovskites (HOIPs) in photovoltaic (PV) devices is made possible by, among other things, outstanding semiconducting properties: long real charge carrier diffusion lengths, L, of up to 5 and possibly even 10 μm, as well as a lifetime τ of ∼1 μs or more in single-crystal and polycrystalline films. Top electronic transport materials will have a high “μτ” product, the product of the charge carrier mobility, μ, and lifetime. This is closely related to the diffusion length, τ = L D ( ) , where D is the carrier diffusion coefficient given as D = (μq/kBT), where q is the electron charge, kB is the Boltzmann constant, and T is the absolute temperature. Long lifetimes, which imply slow recombination and low trapping probabilities, do not automatically imply high mobilities, which are limited by scattering. Charge carrier mobilities in HOIPs are often described as “high”, but this statement warrants some scrutiny. HOIP mobilities are often compared to those of charge carriers in organic semiconductors (see Table 1) and are then indeed