Ascertaining the Transient State Pivotal for Fast Carrier Migration in Halide Perovskites

The perovskite lattice is well known for its soft nature and dynamic disorder. However, it remains elusive as to how the lattice disorder essentially affects the optoelectrical properties of perovskite. In this work, clear pictures of perovskite disorder patterns at the atomic scale are obtained through the refinement of measured pair distribution functions with our newly developed search algorithm. On this basis, we discovered transient states amid the exchange of the lattice orientation. The transient states cause strong phonon couplings, which soften the perovskite lattice and lead to a low thermal conductivity. More importantly, the transient states have narrow bandgaps that fit well into the gap of the stable state, which makes them intrinsic carrier transportation layers that effectively promote the separation and migration of carriers.