Understanding the structural dynamics of 2D perovskites upon photoexcitation is crucial for optimizing their performance in optoelectronic devices. However, directly visualizing these structural changes has remained challenging.
In a recent study published in Nature Communications, researchers from EPFL's Laboratory of Ultrafast Spectroscopy and the Max Planck Institute for Solid State Research employed ultrafast electron microscopy to capture the real-time structural dynamics of 2D perovskite thin films with atomic-scale resolution.
"We were able to directly observe the lattice distortions and atomic displacements that occur within the 2D perovskite structure upon photoexcitation," explains Dr. Antoine G\"orgens, a postdoctoral researcher in the Laboratory of Ultrafast Spectroscopy. "This allowed us to gain unprecedented insights into the fundamental mechanisms underlying the photophysics of these materials."
By analyzing the ultrafast electron microscopy data, the researchers revealed that the photoexcitation of 2D perovskites leads to a rapid lattice expansion and a transient formation of a polar phase. These structural changes modulate the electronic bandgap and enhance the exciton binding energy, which are key factors for efficient light absorption and charge separation in photovoltaic devices.
"Our study provides direct experimental evidence for the dynamic structural behavior of 2D perovskites upon photoexcitation," says Prof. Majed Chergui, the Director of the Laboratory of Ultrafast Spectroscopy. "This knowledge is essential for further optimizing the performance of 2D perovskite-based optoelectronic devices and for pushing the boundaries of their potential applications."
