Surface-Engineered Perovskite Nanocrystal Films for High-Efficiency and Tunable Light-Emitting Diodes

Background

Perovskite light-emitting diodes (PeLEDs) have emerged as a promising technology in the field of optoelectronics due to their tunable emission wavelengths, high color purity, and the potential for low-cost, solution-based fabrication. These attributes make PeLEDs attractive for applications in displays, lighting, and optical communication. The unique crystal structure of metal-halide perovskites allows for efficient charge carrier transport and strong light emission, positioning them as viable alternatives to traditional organic and inorganic LEDs. However, to fully realize their commercial potential, PeLEDs must achieve high external quantum efficiencies (EQE), operational stability, and scalability in manufacturing processes.

Despite significant progress, current approaches to fabricating perovskite LEDs face persistent challenges that limit device performance and reliability. One of the primary issues is the presence of undercoordinated lead, tin, and halide ions on the surface of perovskite nanocrystals, which act as trap states that facilitate non-radiative recombination, thereby reducing light emission efficiency. Conventional methods often fail to achieve comprehensive surface passivation, especially at the nanocrystal scale, leading to incomplete coverage and persistent trap-mediated losses. Additionally, attempts to control nanocrystal size and film morphology can inadvertently induce phase segregation or poor crystallinity, further degrading device performance. These limitations underscore the need for more effective strategies to engineer the surface chemistry of perovskite nanocrystals, ensuring both high efficiency and long-term stability in PeLED devices.

Technology

This technology centers on the precise engineering of perovskite nanocrystal surfaces to dramatically enhance the efficiency and stability of light-emitting diodes (LEDs). By employing a dual-ligand strategy in the precursor solution—combining an excess of bulky organoammonium halide ligands with small ligands such as methylammonium iodide—the approach ensures comprehensive passivation of undercoordinated lead, tin, and halide ions on the nanocrystal surface. The bulky ligands regulate nanocrystal grain size to 5-10 nm and prevent the formation of undesirable low-dimensional phases, while the small ligands access and passivate surface sites inaccessible to the larger molecules. This synergy minimizes non-radiative recombination, promotes radiative recombination, and results in exceptionally high external quantum efficiencies (EQE), exceeding 15% for visible LEDs and around 5% for near-infrared (NIR) LEDs. The emission wavelength is tunable by adjusting the composition of lead and tin in the perovskite, and the films are deposited using scalable solution-based methods such as spin coating.

What differentiates this technology is its holistic and generalizable surface passivation strategy, which addresses a fundamental bottleneck in perovskite LED performance: the elimination of surface trap states that cause non-radiative losses. Unlike conventional methods that rely on a single type of ligand or post-synthetic treatments, this dual-ligand approach ensures full surface coverage and coordination of the perovskite nanocrystals during film formation. The use of specifically tailored bulky ligands—particularly fluorinated phenylmethylammonium derivatives—further enhances film crystallinity, smoothness, and device efficiency. This method not only achieves record-high EQEs and operational stability, but also enables tunable emission across the visible and NIR spectrum without phase segregation. The compatibility with scalable, low-temperature solution processing makes it highly attractive for commercial applications in displays, lighting, and optical communications, setting a new benchmark for perovskite LED technology.

Benefits

• Significantly enhanced external quantum efficiency (EQE) exceeding 15% for visible LEDs and around 5% for near-infrared LEDs.
• Comprehensive surface passivation of perovskite nanocrystals reduces non-radiative recombination and trap states, improving device performance.
• Dual-ligand strategy (bulky organoammonium halides plus small ligands) enables precise nanocrystal size control (5-10 nm) and smooth, high-quality films.
• Emission wavelength tunability across visible and near-infrared spectra (850–950 nm) via mixed lead-tin perovskite compositions and halide adjustments.
• Improved film crystallinity and morphology using fluorinated bulky ligands, leading to higher photoluminescence quantum yield and carrier lifetime.
• Scalable, solution-based fabrication methods (spin coating with anti-solvent treatment) suitable for large-area device production.
• Stable device operation with minimal spectral shift, low leakage current, and good shelf life under inert atmosphere.
• Compatibility with standard PeLED device architectures incorporating transparent electrodes and charge transport layers for efficient charge injection and recombination.

Applications

• High-efficiency display backlighting
• Visible and NIR LED lighting
• Optical communication devices
• Wearable biosensors
• Infrared imaging systems

Additional info

This methodology engineers perovskite nanocrystal surface chemistry for high-efficiency light-emitting diodes. A dual-ligand precursor solution, incorporating bulky organoammonium and small ligands, passivates undercoordinated surface ions. This eliminates trap states, minimizing non-radiative recombination and boosting radiative efficiency. Scalable solution processes yield devices with external quantum efficiencies exceeding 15% for visible and 5% for near-infrared emission.