Unveiling Structurally Engineered Carrier Dynamics in Hybrid Quasi-Two-Dimensional Perovskite Thin Films toward Controllable Emission.

Quasi-two-dimensional Ruddlesden-Popper perovskites driving carrier self-separation have rapidly advanced the development of high-performance optoelectronic devices. However, insightful understanding of carrier dynamics in the perovskites is still inadequate. The distribution of multiple perovskite phases, crucial for carrier separation, is controversial. Here we report a systematic study on carrier dynamics of spin-coated (C6H5CH2CH2NH3)2(CH3NH3)n-1PbnI3n+1 (n = 3 and 5) perovskite thin films. Efficient electrons transfer from small-n to large-n perovskite phases, and holes transfer reversely with time scales from ∼0.3 to 30.0 ps. The multiple perovskite phases are arranged perpendicularly to substrate from small to large n and also coexist randomly in the same horizontal planes. Further, the carrier separation dynamics is tailored by engineering the crystalline structure of the perovskite film, which leads to controllable emission properties. These results have important significance for the design of optoelectronic devices from solar cells, light-emitting diodes, lasers, and so forth.