  Lead-halide perovskites attracted attention as materials for high-efficiency
solar cells and light emitting applications. Among their attributes are
solution processability, high absorbance in the visible spectral range and
defect tolerance, as manifested in long photocarrier lifetimes and diffusion
lengths. The microscopic origin of photophysical properties of perovskites is,
however, still unclear and under debate. Here, we have observed an interesting
universal scaling behavior in a series of (hybrid and all-inorganic) perovskite
single crystals investigated via simultaneous measurements of the Hall effect,
photoconductivity and photoluminescence. A clear correlation between
photoconductivity and photoluminescence as functions of the incident photon
flux is observed. While photoconductivity exhibits a crossover in the power-law
dependence between power exponents 1 and 1/2, photoluminescence exhibits a
crossover between power exponents 2 and 3/2. This correlation is found in all
the studied compounds irrespective of the cation type (organic or inorganic) or
crystallographic phases. We propose phenomenological microscopic mechanisms
that explain these interesting non-trivial power exponents and crossovers
between them in this broad class of lead-halide perovskites.
