Revealing Ultrafast Carrier Dynamics of Hybrid Perovskites at Various Stages of Nucleation and Growth Kinetics

With hybrid organic–inorganic perovskites expanding their technological reach, from photovoltaic solar cells that operate at low carrier densities (1011 − 1013 cm−3) to light‐emitting diodes and lasers that operate at higher carrier densities (1013 − 1019 cm−3), it is critical to know how microstructure dictates carrier dynamics at varying injected carrier densities. For fabrication at scale, it is equally critical to know how quickly during the growth process do hybrid perovskites develop their characteristic optoelectronic properties. This work reports on a facile fabrication method that “freezes” different stages of nucleation and growth kinetics of prototypical hybrid perovskite on the same substrate—providing a unique strategy to assess differences in optoelectronic properties and carrier dynamics from nascent nucleating microcrystals to large‐grain thin films. The solution‐processed fabrication technique, optimized to control the nucleation density of an intermediate phase, successfully decouples the nucleation and growth steps that lead to large‐grain thin films. Ultrafast broadband absorption microscopy finds that the nucleating microcrystals already possess the optoelectronic properties of hybrid perovskites and share similar femtosecond‐to‐nanosecond dynamics as large‐grain thin films. When compared to the large‐grain thin films, the confining microcrystals exhibit enhanced carrier interactions, marked by an increase in bimolecular and Auger recombination rates. This work examines how fundamental signatures of carrier dynamics in prototypical metal halide hybrid perovskites evolved at key stages of their nucleation and growth kinetics. Ultrafast broadband absorption microscopy quantifies how changes in the microstructured thin film affect the degree of carrier localization, optical band gap and many‐body interactions such as Auger processes.