Perovskite LED

Researchers from Hebei University of Technology, the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, and the Chinese University of Hong Kong have developed a fabrication method for perovskite light-emitting diodes (PeLEDs) that works entirely in open air, lifting the photoluminescence quantum yield (PLQY) of the emissive film from 6% to 64% and yielding devices with a peak external quantum efficiency (EQE) of 10.5% and an operational lifetime of 125.6 minutes.

PeLEDs are attractive for next-generation displays and lighting thanks to their narrow emission linewidths, high color purity and solution processability, and devices spanning blue, green, red and near-infrared have already achieved EQEs above 20%. However, perovskite films are highly sensitive to atmospheric moisture and oxygen, which normally forces fabrication into tightly controlled inert atmospheres - adding cost and complexity that stands in the way of scaling the technology up commercially. One common workaround adds hydrophobic organic ammonium halides to the perovskite precursor, which induce quasi-2D structures that confine excitons and make the film more moisture-tolerant. But conventional versions of this approach, built on hydrophobic long-chain ligands, bring their own problems: the ligands' bulk widens the spacing between quantum wells in a way that hampers carrier injection and interlayer energy transfer, and ligand aggregation tends to produce an excess of low-n phases that introduce additional non-radiative recombination. Producing well-regulated quasi-2D films has also typically required precisely controlled antisolvent dripping using toxic, volatile solvents such as diethyl ether or chlorobenzene - a process sensitive to timing, solvent diffusion and humidity, giving a narrow processing window and poor reproducibility, especially in ambient conditions.

Researchers from Shanghai University, Jiangsu University of Science and Technology, Chinese Academy of Sciences, Tongji University, Jilin University, Southern University of Science and Technology, University of Nottingham and Okinawa Institute of Science and Technology have developed efficient and stable perovskite light-emitting diodes (PeLEDs) with saturated blue emission, by building hydrogen-bonding networks both inside the perovskite layer and at its interface using a pair of isomeric molecules. 

Over the past decade PeLEDs have grown brighter and cheaper to make, and compositional tuning has taken them across the visible spectrum, with red and green devices now matching - and in places beating - rival LED materials. Blue electroluminescence, however, has lagged badly behind, and that gap alone has kept full-color perovskite displays out of reach. The reason is structural - blue emission requires a wider bandgap, which in turn demands a higher operating voltage from the device. In a material held together by ionic bonds, that extra electrical stress aggravates the instability of the perovskite's octahedral framework, and the lattice degrades quickly. The result, until now, has been blue devices that are both dimmer and shorter-lived than their red and green counterparts.

Fuzhou University researchers have developed a multifunctional ligand engineering strategy that enables efficient and stable near-infrared perovskite quantum-dot LEDs (NIR-PQLEDs) fabricated entirely under ambient air conditions.

Metal halide perovskite quantum dots (PQDs), particularly formamidinium lead iodide (FAPbI₃), are attractive for NIR emission above 750 nm due to their tunable bandgaps, high color purity, and solution processability. These properties make them promising for applications such as biomedical imaging, night vision, and optical communication. However, despite rapid efficiency improvements in recent years - reaching EQEs above 20% in optimized systems - high-performance NIR-PQLED fabrication still typically relies on inert environments due to the extreme air sensitivity of PQDs.

A joint team from Seoul National University, led by Prof. Lee Tae-woo, and the University of Cambridge, led by Prof. Samuel Stranks, has demonstrated a new thermodynamically guided vacuum-deposition process for perovskite light-emitting diodes (PeLEDs), aimed at next-generation display applications. 

Patterns and array perovskite light-emitting devices on a 7 cm by 7 cm large-area substrate. Image credit: Seoul National University College of Engineering

Vapor deposition is attractive for industry because it is compatible with existing OLED infrastructure and scalable to large areas, but conventional perovskite vapor growth has been limited by kinetically driven crystallization, which produces mixed-dimensional phases, nanoscale heterogeneity, broadened energy landscapes and ultimately lower device efficiencies. 

Researchers from Peking University, Eindhoven University of Technology, Chinese Academy of Sciences, Beijing Institute of Technology and University of Science and Technology of China have reported an effective strategy to resolve a long-standing trade-off in blue perovskite light-emitting diodes (PeLEDs), enabling high-efficiency devices through polymerization-driven nanocrystal confinement.

Metal halide perovskites are highly attractive for LED applications due to their excellent luminescence properties, but device performance has been constrained by a fundamental contradiction during in situ nanocrystal formation: achieving both high crystallinity and small crystal size. Small nanocrystals are essential for efficient radiative recombination, yet they are typically prone to structural disorder and defect formation, while larger crystals exhibit improved crystallinity but reduced emission efficiency. To address this, the researchers developed an in situ polymerization approach in which polymerizable ligands coordinate with perovskite precursor species during film formation. These ligands subsequently form a polymer network that imposes nanoscale spatial confinement on the growing nanocrystals. This confinement limits crystal growth while maintaining sufficient structural flexibility for lattice reorganization.

Zhengzhou University researchers have developed a dipole-engineering strategy that significantly improves the power efficiency of blue perovskite quantum dot LEDs, addressing a long-standing bottleneck in the field.

Blue perovskite LEDs are critical for applications such as full-color displays, general lighting, and optical signal transmission, but their power efficiency (PE) has lagged behind despite external quantum efficiencies (EQEs) exceeding 25%. This limitation is mainly due to the wider bandgap of blue emitters, which requires higher driving voltages, as well as insulating organic ligands on quantum dot (QD) surfaces that hinder carrier transport and increase energy consumption.

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Researchers from Hanyang University, Ajou University and POSTECH have developed a hydrolysis-assisted ligand-exchange strategy that significantly improves charge transport and efficiency in metal halide perovskite nanocrystal (MHP NC) LEDs, achieving a record external quantum efficiency (EQE) of 31.7% for green-emitting devices.

Schematic illustration of the ligand-exchange and surface-functionalization process of MHP NCs. Image from: Advanced Materials

MHP nanocrystals are widely considered promising candidates for next-generation light-emitting diodes due to their excellent color purity and high radiative efficiency. However, their performance has been limited by the presence of long-chain native ligands on the nanocrystal surface. These ligands are weakly bound and electrically insulating, which hinders charge injection and transport, introduces trap states, and ultimately leads to energy losses in devices. To address these challenges, the researchers introduced a multifunctional π-conjugated pyridine carboxamide (PCA) ligand via a hydrolysis-assisted, one-step ligand-exchange process. This approach removes the original insulating ligands under mild conditions and replaces them with PCA, which provides multidentate, multisite surface coordination. The ligand acts as a strong anchoring group while simultaneously enabling enhanced electronic coupling between nanocrystals and inducing n-type surface functionalization.

Researchers from the University of Science and Technology of China and the University of Colorado Boulder have demonstrated a perovskite diode that acts as both an efficient solar cell and a high‑efficiency LED using the same 800 nm thick absorber layer.

The device embeds porous micrometer‑scale alumina (Al₂O₃) “sponge” islands (∼5 μm wide, 0.5 μm tall) inside the perovskite, allowing a layer thick enough for photovoltaics to also extract light efficiently like an LED. In conventional devices, perovskite LEDs rely on ultrathin, discontinuous layers of about 50 nm, whereas efficient solar cells need layers roughly sixteen times thicker; this architecture reconciles those opposing thickness requirements in a single stack. Surface‑functionalized alumina nanoparticles assemble electrostatically into these islands: one population is coated with negatively charged Me‑4PACz, the other with positively charged ODA, giving a porous, low‑index network the perovskite can grow through without disrupting charge transport.

A recent University at Buffalo (SUNY) study has shown that a fluorinated multifunctional ligand can dramatically improve both efficiency and stability in deep-blue CsPb(Br/Cl)₃ perovskite nanocrystal LEDs by suppressing defect formation and halide ion migration.

Deep-blue PeLEDs require emission in the 460-470 nm range, which can be realized either with mixed-halide CsPb(Br/Cl)₃ nanocrystals or with strongly quantum-confined CsPbBr₃ nanoplatelets. Quantum-confined CsPbBr₃ NPLs have demonstrated 461 nm emission with a 13 nm FWHM and 96% PLQY, enabling REC.2020-compliant deep blue (CIE (0.135, 0.046)), but EQE remains below 7%. Mixed-halide CsPb(Br/Cl)₃ offers a more direct compositional route, yet is prone to halide vacancies and instability, as seen in formamidinium-doped CsPb(Cl₀.₅Br₀.₅)₃ PeNCs that reach 1452 cd m⁻² but only 5% EQE and a peak at 474 nm, slightly red of the target window. In the new work, HFPA-engineered CsPb(Br/Cl)₃ emitters are tuned specifically for operation in the 460-470 nm pure-blue range, directly targeting display-relevant color coordinates.