China unveils brightest pure-red perovskite LEDs with record-breaking 24.2% efficiency

Scientists in China have announced the creation of pure-red perovskite light-emitting diodes (PeLEDs) that are the brightest and most efficient ever made.

The breakthrough, achieved by a team at the University of Science and Technology of China (USTC), solves a critical flaw that has previously limited the performance of these highly promising materials.

The research team has successfully engineered PeLEDs that hit a peak external quantum efficiency of 24.2% and a stunning maximum brightness of 24,600 candelas per square meter (cd m ⁻² ).

Pure-red PeLEDs are considered crucial for the development of next-generation vivid displays and energy-efficient lighting solutions. However, a fundamental trade-off between efficiency and brightness has long hampered their progress.

This was due to "carrier leakage" in commonly used 3D mixed-halide perovskite materials like CsPbI _3−x Br _x , where electrical charges would escape before they could be converted into light.

"While three-dimensional (3D) mixed-halide perovskites like CsPbI _3-x Br _x offer excellent charge transport, their efficiency plummets under high current due to unresolved carrier leakage," explained the team.

Developing specialized diagnostic tool

The USTC research group, led by Professors Yao Hongbin, Fan Fengjia, Lin Yue, and Hu Wei, tackled this problem head-on.

To address this limitation, researchers led by Prof. Yao Hongbin, Fan Fengjia, Lin Yue, and Hu Wei at USTC developed a specialized diagnostic tool, electrically excited transient absorption (EETA) spectroscopy. This allowed them to conduct real-time analysis of carrier dynamics within operating devices.

The team was able to precisely identify the cause of this leakage.

"They found that the hole leakage into the electron transport layer—previously undetected due to a lack of in situ characterization methods—is the primary culprit behind efficiency roll-off," highlighted the press release.

"To enhance the carrier confinement capability of perovskites, the researchers engineered a 3D intragrain heterostructure within the perovskite emitter, which embeds narrow-bandgap light-emitting regions within a continuous [PbX ₆ ] ^4- framework, separated by wide-bandgap barriers that confine carriers."

These barriers effectively trap the charge carriers and force them to convert into light much more efficiently.

Overcoming significant hurdle in perovskite optoelectronics

A crucial component of this new architecture is a molecule named p-Toluenesulfonyl-L-arginine (PTLA). The scientists discovered that PTLA's unique chemical structure allows it to anchor itself within the perovskite lattice.

"PTLA expanded the lattice locally, creating wide-bandgap phases without disrupting structural continuity," explained the researchers.

"High-resolution transmission electron microscopy and ultrafast spectroscopy confirmed the seamless carrier transfer between the heterostructure's phases and suppressed hole leakage."

The optimized PeLED devices demonstrated unprecedented performance. The new PeLEDs maintain an impressive 10.5% efficiency even when operating at nearly 90% of their peak, record-setting brightness (22,670 cd m ⁻² ).

"Stability tests revealed a half-lifetime of 127 hours at 100 cd m ^-2 , with minimal spectral shift during operation," concluded the press release .

By combining advanced diagnostic techniques with smart material engineering, the USTC scientists have overcome a significant hurdle in perovskite optoelectronics and opened the door for a new generation of brilliant, pure-red light sources for a wide array of technologies.

The study has been published in the journal Nature.