Researchers from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences have addressed a critical challenge in perovskite light-emitting diodes (PeLEDs) by identifying and targeting the root cause of efficiency loss at high brightness, and enabled record-breaking device performance by introducing a novel material design.
Using a self-developed diagnostic tool called electrically excited transient absorption (EETA) spectroscopy, the researchers captured real-time carrier dynamics in operating devices. 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.
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 [PbX6]4− framework, separated by wide-bandgap barriers that confine carriers.
The key to this strategy is the molecule p-Toluenesulfonyl-L-arginine (PTLA) which bonds strongly to the perovskite lattice via multiple functional groups (guanidino, carboxyl, amino, and sulfonyl). PTLA expanded the lattice locally, creating wide-bandgap phases without disrupting structural continuity. High-resolution transmission electron microscopy and ultrafast spectroscopy confirmed the seamless carrier transfer between the heterostructure's phases and suppressed hole leakage.
The optimized PeLEDs exhibited unprecedented performance, and achieved a peak external quantum efficiency (EQE) of 24.2% and a maximum luminance of 24,600 cd m-2-the brightest pure-red PeLED reported to date, according to the team. Stability tests revealed a half-lifetime of 127 hours at 100 cd m-2, with minimal spectral shift during operation.
This work bridges a critical gap in perovskite optoelectronics, combining advanced diagnostics with innovative material engineering
