Korea Institute of Science and Technology (KIST), Advanced Analysis and Data Center
About
The Advanced Photoelectron Spectroscopy Laboratory (APS-NE) utilizes photoelectron spectroscopy (XPS, UPS) and inverse photoemission spectroscopy (IPES) as its core analytical techniques to precisely elucidate the complex electronic structures, including binding energy, work function, ionization energy, electron affinity, and bandgap, of next-generation nanomaterials. Our research team focuses on understanding and controlling the unique electronic properties of 2D semiconductors, perovskites, organic and molecular semiconductors, and their complex heterojunction structures. Our ultimate goal is to establish a clear physical understanding of the energy level alignment, charge transport mechanisms, defects, and degradation processes that dictate the performance of next-generation semiconductor devices used in high-efficiency solar cells, light-emitting diodes, and photodetectors. Recently, we have expanded our research to integrate advanced machine learning techniques with vast amounts of material and surface analysis data. By automating the interpretation of complex photoelectron spectroscopy spectra and training machine learning algorithms on massive in-situ experimental datasets, we seek to uncover subtle changes in electronic structures that are difficult to identify through conventional methods. Furthermore, leveraging measured energy levels and interfacial property data, we are developing machine learning-based design technologies for next-generation materials. This data-driven approach allows us to predict the behavior of novel optoelectronic materials and inversely propose optimal material combinations to realize highly efficient devices.
Exciton Binding Energy Modulation in 2D Perovskites: A Phenomenological Keldysh Framework
Understanding 2D perovskite electronic structures requires separating dielectric screening from structural distortion. By systematically varying organic spacers, we maintained the inorganic framework to completely isolate these screening effects. Direct measurements using Low-Energy Inverse Photoemission Spectroscopy (LEPES) revealed a notable divergence: increasing spacer length significantly widens the quasiparticle bandgap and exciton binding energy, while the exciton energy itself remains constant. We rationalized these dependencies by applying the Keldysh model with a spatially averaged phenomenological dielectric constant. Our well-controlled approach provides an experimentally validated basis for predicting excitonic properties and engineering advanced quasi-2D semiconductors.
Advanced Functional Materials e20461 (2025) [IF: 19.92, JCR: 3.26 %, Corresponding author]
Kinetics Control of Mithrene Formation in a High-Pressure Inert Environment: A Robust Solvent-Free Route to Superior-Quality Films
Metal organic chalcogenolates (MOCs), such as mithrene (AgSePh), are highly promising 2D hybrid materials for next-generation optoelectronics due to their sharp blue emission and environmental stability. However, traditional solvent-assisted synthesis often introduces chemical impurities and degrades film quality. To overcome these critical limitations, this study presents a robust, solvent-free synthesis strategy that leverages precise pressure and temperature control within an inert gas environment to optimize reaction kinetics. Comprehensive spectroscopic and structural analyses, including GIWAXS, XPS, and PL spectroscopy, demonstrate that our method yields mithrene thin films with drastically improved crystallinity and significantly enhanced excitonic emission. Notably, this high out-of-plane structural coherence enabled the discovery of a previously unreported excitonic feature (Xα). This advanced fabrication route paves the way for integrating superior-quality MOCs into advanced semiconductors and catalysts.
ACS Applied Materials & Interfaces (2025) [IF: 8.2, JCR: 15.66 %, Corresponding author]
