| 초록 |
Charge carrier mobility (ratio between the drift velocity and the electric field), has proven to be much more challenging to quantify. Indeed, an accurate estimation of charge carrier density is hindered by early-time recombination, the branching ratio of excitons to free-carriers and sensitivity to short-range conductivity unlikely influenced by scattering events at grain boundaries and charge trapping. It is important to understand the long-range charge transport within the metal halide perovskite for optimisation of operating devices, where the charges have to travel over on the order of microns, and if these properties change in different carrier density regimes, or through different methods of processing the films. Here we introduce an advanced methodology: Transient photoconductivity. We accurately estimated the internal free-carrier density during photo-excitation, accounting for both early-time recombination and exciton-to-free-carrier branching ratios to determine long-range charge carrier mobility in metal halide perovskite thin films and single crystals, to be invariant over many orders of magnitude of charge density. We also demonstrate that the processing method of perovskite layer has a strong influence on the long-range charge transport. |
