Figure 4. Steady-state photoconductivity and Hall effect measurements in perovskite films and crystals.

(a) μ_Hall in a vapour-grown 100 nm-thick polycrystalline CH₃NH₃PbI₃ film (similar to that shown in Fig. 1b), measured at different photo-excitation densities, is nearly a constant (the dashed line indicates an average value of≈8 cm² V⁻¹ s⁻¹). (b) Photoconductivity and Hall carrier density measured in this film as a function of absorbed photon density. (c) n_Hall(G) in six thin-film samples with very different morphologies and μ_Hall values, showing that bimolecular recombination (n_Hall∝G^1/2) governs all these samples. Hall mobility and the method of fabrication are indicated for each film in the legend. (d) Photoconductivity and Hall carrier density measured in a macroscopic, bulky CH₃NH₃PbBr₃ single crystal (as the ones shown in Fig. 1c) with a (dark) Hall mobility μ_Hall≈60 cm² V⁻¹ s⁻¹ (for holes). Dashed lines in b–d are the power law fits with exponent α=½: n or σ=constant·G^1/2.