Figure 2. Steady-state photoconductivity measured as a function of photo-excitation density in thin films and single crystals of hybrid perovskites.

Measurements are carried out by 4-probe technique under a cw photo-excitation with a blue light (λ=465 nm) in CH₃NH₃PbBr₃ single crystals (red squares), vapour-grown polycrystalline CH₃NH₃PbI₃ films (green triangles) and solution-grown semi amorphous CH₃NH₃PbI₃ films (black circles). Dashed lines are the power law fits, σ_PC∝G^α, with the exponents α=1 or ½ (as indicated). It is clear that bimolecular e–h recombination (α=½) dominates the behaviour at high photo-excitation densities (note the double-log scale).