Researchers at the University of Cambridge, University of Science and Technology of China, Shanghai Jiao Tong University, Soochow University, OIST, Hong Kong University of Science and Technology, Victoria University of Wellington and Kyushu University have demonstrated efficient blue perovskite LEDs based on a mixed two-dimensional–three-dimensional perovskite and a multifunctional ionic additive that enables control over the reduced-dimensional phases, non-radiative recombination channels and spectral stability.
The team reported a series of devices that emit efficient electroluminescence from mixed bromide/chloride quasi-three-dimensional regions, with external quantum efficiencies of up to 21.4% (at a luminance of 22 cd m–2 and emission peak at 483 nm), 13.2% (at a luminance of 2.0 cd m–2 and emission peak at 474 nm) and 7.3% (at a luminance of 6 cd m–2 and emission peak at 464 nm). The devices showed a nearly 30-fold increase in operational stability compared with control LEDs, with a half-lifetime of 129 min at an initial luminance of 100 cd m–2.
To address the challenge of blue perovskite LEDs' development lagging behind that of green, red, and near-infrared perovskite LEDs, the scientists designed a multifunctional ionic additive, Bis(triphenylphosphine)iminium chloride (PPNCl), with multiple charged resonance forms and a dynamic electronic state. This compound enables precise control over the composition and distribution of perovskite phases, effectively suppressing non-radiative recombination channels and ion migration, thereby significantly improving the efficiency and stability of blue perovskite LEDs.
PPNCl interacts with the components of the perovskite via hydrogen bonding, influencing the crystallization process and favoring the transition to high-dimensional phases with enhanced luminescence efficiency. Transient absorption (TA) spectroscopy studies further revealed that PPNCl accelerates energy transfer processes from low-dimensional to high-dimensional phases, suppressing incomplete energy transfer and energy loss due to non-radiative recombination in low-dimensional phases.
Furthermore, PPNCl molecules coordinate with perovskite components and exhibit electrostatic interactions, effectively passivating defects in perovskite films and inhibiting halide ion migration, leading to a significant enhancement in the luminescence efficiency and spectral stability of perovskite films.
The team's findings demonstrate the performance of blue perovskite LEDs close to that of state-of-the-art blue organic LEDs and inorganic quantum dot LEDs and provide a new approach to design multifunctional molecules to boost the performance of perovskite optoelectronic devices.