Temperature and Gate Dependence of Carrier Diffusion in Single Crystal Methylammonium Lead Iodide Perovskite Microstructures.

We investigate temperature-dependent photogenerated carrier diffusion in single-crystal methylammonium lead iodide microstuctures via scanning photocurrent microscopy. Carrier diffusion lengths increased abruptly across the tetragonal to orthorhombic phase transition and reached 200 ± 50 μm at 80 K. In combination with the microsecond carrier lifetime measured by a transient photocurrent method, an enormous carrier mobility value of 3 × 10 cm/V s was extracted at 80 K.

Millimetre-long transport of photogenerated carriers in topological insulators.

Excitons are spin integer particles that are predicted to condense into a coherent quantum state at sufficiently low temperature. Here by using photocurrent imaging we report experimental evidence of formation and efficient transport of non-equilibrium excitons in BiSbSe nanoribbons. The photocurrent distributions are independent of electric field, indicating that photoexcited electrons and holes form excitons.