Seoul National University College of Engineering announced that a joint research team led by Professor Tae-Woo Lee of the Department of Materials Science and Engineering at SNU and Professor Samuel D. Stranks of the University of Cambridge has developed a vapor-deposited perovskite light-emitting diode (PeLED) with world-leading efficiency. The team achieved this by discovering a new X-type perovskite emitter capable of thermodynamically stabilizing a luminescence-favorable phase during the vacuum deposition process.
Perovskites have attracted significant attention as next-generation display materials due to their high efficiency, vivid color emission, and compatibility with existing OLED fabrication processes, enabling implementation without large-scale facility investments. However, in conventional vacuum deposition processes, crystallization is not thermodynamically controlled, leading to rapid and non-uniform crystal growth.
To address this issue, the research team introduced X-type spacer organic molecules to design a new X-type quasi-two-dimensional perovskite emitter, enabling thermodynamically controlled crystal growth on the substrate and the formation of a uniform emissive phase favorable for high-efficiency light emission. In addition, the team developed a hetero-scaffold that promotes selective crystal phase growth, providing a strategy for precise crystallization control in vacuum deposition. As a result, they successfully realized PeLEDs with both high emission efficiency and high color purity.
The findings were published on July 1 in Nature Nanotechnology, one of the most prestigious journals in the field of nanotechnology.
Perovskites (typically with a three-dimensional ABX₃ structure, where A is a cation, B is a metal cation, and X is a halide anion) are emerging as promising next-generation display materials due to their high color purity, excellent emission efficiency, low material cost, and compatibility with vacuum deposition processes—unlike conventional quantum dots. However, high efficiency alone is insufficient for industrial application. Large-area production, uniform thin-film formation, precise thickness control, and pixel patterning must all align with existing display manufacturing processes.
Currently, vacuum deposition* is widely used in OLED production. If perovskites can be fabricated using this method, compatibility with existing infrastructure would significantly enhance commercialization potential.
* Vacuum deposition: a manufacturing technique in which materials are vaporized under vacuum and deposited as thin films on a substrate.
However, perovskite vacuum deposition involves complex simultaneous reactions of multiple precursors* on the substrate to form crystals. When this process becomes too rapid and complicated, multiple crystal phases can form, resulting in non-uniform films with reduced emission efficiency and color purity.
* Precursor: a starting material that undergoes chemical transformation to form the final substance.
Thus, beyond simple process optimization, a new material design strategy capable of controlling the formation pathway of perovskite crystals is essential for commercialization.
To overcome these challenges, the team developed a novel X-type quasi-two-dimensional perovskite* emitter distinct from conventional quasi-2D structures through vacuum deposition. This represents a new material and fabrication strategy for achieving highly uniform, high-efficiency, and high–color purity PeLEDs.
* Quasi-two-dimensional perovskite: A structure in which perovskite layers are stacked in multiple layers (e.g., single-layer, double-layer, triple-layer), with each layer separated by spacer molecules. Conventionally, quasi-two-dimensional perovskites have been fabricated by introducing bulky organic molecules into the A-site.
The team introduced X-type spacer* molecules, which strongly coordinate with central lead ions during crystallization, suppressing disordered crystal growth and promoting the selective formation of the most energetically stable crystal phase. This enabled the development of a thermodynamic phase stabilization* strategy that directs the formation of the desired phase during deposition.
* X-type spacer: a molecule that substitutes halide sites while inducing separation between perovskite layers.
* Thermodynamic phase stabilization: a method of controlling phase formation by favoring energetically stable structures within a specific temperature range.
Additionally, the team developed a nanoscale hetero-scaffold* by chemically bonding X-type spacer molecules with lithium fluoride (LiF)*. This structure prevents random crystal growth of perovskites and promotes uniform crystallization across the film.
* Hetero-scaffold: a uniform seed layer formed by chemically bonded LiF and X-type spacer molecules.
* Lithium fluoride: a lithium-based compound used to enhance electronic device performance.
Through this approach, the team achieved perovskite thin films with a photoluminescence quantum yield (PLQY)* exceeding 85%. The resulting PeLEDs exhibited an external quantum efficiency (EQE)* of 21.9% and a narrow emission linewidth* of 16.8 nm, demonstrating both high efficiency and excellent color purity—representing world-leading performance among vapor-deposited PeLEDs.
* Photoluminescence quantum yield: ratio of emitted light energy to absorbed light energy.
* External quantum efficiency: efficiency of light emission in LED devices.
* Emission linewidth: spectral width of emitted light; narrower values indicate higher color purity.
The team also confirmed that these PeLEDs can be fabricated on large-area substrates, flexible platforms, and patterned structures, highlighting their applicability to real-world display manufacturing.
This study provides a new direction for the commercialization of perovskite display by resolving a key challenge in vapor deposition—lack of thermodynamic phase control during film growth—and enabling uniform fabrication of highly efficient emitters with high– color purity emitters.
In particular, the X-type quasi-2D perovskite developed in this work represents a fundamentally new material design strategy that controls the crystallization process itself, rather than a simple additive approach. This strategy addresses major limitations of conventional vacuum deposition, including film non-uniformity, low color purity, and phase mixing.
The findings hold significant industrial implications. Given that vacuum deposition is already a core process in OLED manufacturing, this technology offers high compatibility with existing infrastructure, reducing capital investment compared to transitions such as LCD to OLED. Furthermore, the technology enables high efficiency even at ultra-small pixel sizes, making it suitable for ultra-high-resolution displays, AR/VR microdisplays, next-generation color-conversion layers, and emissive devices.
Professor Tae-Woo Lee stated, ""This study is significant because it provides a fundamental understanding of how perovskite precursors react and crystallize on a substrate during vacuum deposition and, based on this understanding, establishes a new X-type quasi-2D perovskite emitter design. By realizing perovskite light-emitting devices with world-leading efficiency and color purity through a vacuum-deposition process compatible with existing OLED manufacturing infrastructure, this work is expected to provide a key technological foundation for accelerating the practical implementation of ultra-high-resolution displays and AR/VR microdisplays."
Co-first author Chan-Yul Park, a Ph.D. candidate at SNU, is conducting research on crystallization control and high-efficiency PeLED development based on vacuum deposition.
Co-first author Joo Sung Kim, who earned his Ph.D. at SNU, is currently a Marie Curie Fellow and postdoctoral researcher in Professor Stranks' group at the University of Cambridge, focusing on material design and photophysical analysis of perovskite optoelectronic devices.
The research team plans to further expand the scalability and patterning capabilities of vapor-deposited PeLEDs, aiming to accelerate the development of next-generation display technologies.
This work was carried out through a collaborative research effort led by Seoul National University, with participation from research institutions at the University of Cambridge. It was supported by the Leader Research Program (RS-2025-00560490) and the Nano-Materials Technology Development Program (2022M3H4A1A04096380), funded by the Ministry of Science and ICT and the National Research Foundation of Korea.
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Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of 'fostering leaders for global industry and society.' In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.
