A team at the Institute for Basic Science (IBS) Center for Molecular Spectroscopy and Dynamics (CMSD) — led by Director CHO Minhaeng (Professor of Chemistry, Korea University) and Professor YOON Tai Hyun (Department of Physics, Korea University) — has developed a powerful new spectroscopic technique that enables real-time tracking of how perovskite nanomaterials change under light.
The technique, called asynchronous and interferometric transient absorption spectroscopy (AI-TA), provides ultrafast measurements of excited-state dynamics and structural transformations in light-responsive materials. It overcomes major limitations of traditional ultrafast spectroscopy, which often requires long data acquisition times and can damage light-sensitive samples during measurement.
“We can now simultaneously observe not just how a material reacts to light but also how it transforms during the reaction itself,” explained Director CHO Minhaeng. “This makes AI-TA a powerful tool for real-time analysis of complex nanoscale processes.”
Perovskite materials are considered promising candidates for next-generation optoelectronic devices like solar cells and LEDs. Conventional femtosecond (10⁻¹⁵ second) laser-based techniques allow for ultrafast observation of their carrier dynamics, reflecting chemical and physical properties. However, such properties are highly sensitive to external factors, such as light, making it difficult to study how they behave in real-world conditions. Especially for ultrafast spectroscopy, the laser pulses used for observation can degrade or alter the sample.
The IBS team addressed this challenge by dramatically shortening measurement time using AI-TA, which relies on two precisely synchronized lasers to capture spectrally and temporally resolved snapshots of the material's transient state. With this technique, the IBS researchers could observe phenomena — including charge carrier dynamics, compositional shifts, and structural reorganizations — over broad timescales ranging from femtoseconds to several minutes.
“AI-TA is evolving into a time-resolved spectroscopic technique that leverages the precision of optical frequency comb technology to investigate molecular reactions in the femtosecond regime,” added Professor YOON Tai Hyun, co-corresponding author of the study.
The researchers applied AI-TA to two types of perovskite systems. In the first, they studied light-induced halide substitution in cesium lead halide nanocrystals, showing that increasing the chloride-to-bromide ratio led to higher bandgap energies and faster charge-carrier dynamics. In the second, they investigated light-driven transformation and agglomeration of colloidal perovskite nanoplatelets, observing how energy loss in hot carriers changed depending on agglomeration, and revealing a nuanced relationship between optical behavior and structural evolution.
“AI-TA offers a new way to study the dynamics of novel materials and various chemical substances that can be easily altered by light and other factors,” said Dr. HAN Gi Rim, first author of the study. “This experiment marks the first step in showcasing the potential of AI-TA, and we look forward to expanding its applications in future research.”
This research represents a technological leap in capturing the real-time evolution of light-sensitive materials during laser measurements. Beyond perovskites, the AI-TA method has the potential to accelerate discoveries in fields ranging from quantum materials and catalysis to next-generation optoelectronic and photonic systems.