Engineering Interface Polarity via Halide‐Functionalized Self‐Assembled Monolayers for NiO‐Based QLEDs with High External Quantum Efficiency

Why It Matters

The breakthrough dramatically improves charge balance and reduces interfacial traps, unlocking higher efficiency for next‑generation display panels that rely on inorganic hole‑injection layers.

Key Takeaways

• Halide‑SAMs deepen Cu:NiO valence band.
• Dipole reduces hole‑injection barrier.
• High polarizability strengthens van der Waals anchoring.
• Dense SAM layer suppresses surface traps.
• Record 26.95% EQE for green QLEDs.

Pulse Analysis

Quantum dot light‑emitting diodes (QLEDs) have emerged as a leading candidate for high‑brightness, color‑pure displays, yet their commercial rollout is hampered by inefficient inorganic hole‑injection layers (HILs). Conventional HILs often suffer from mismatched energy levels and surface defects that create non‑radiative recombination pathways, limiting external quantum efficiency (EQE). By focusing on interface polarity, researchers can align energy bands more favorably, a strategy that complements existing material improvements in quantum dot emissive layers.

The study leverages halide‑functionalized (2PACz) self‑assembled monolayers to engineer the Cu‑doped NiO surface. The halide substituents generate a pronounced dipole moment, shifting the NiO valence band deeper and easing hole injection into the transport layer. Density functional theory calculations reveal that the large polarizability of the halides amplifies van der Waals dispersion, producing a tightly bound, densely packed SAM. This molecular architecture not only passivates surface traps but also stabilizes the interface against environmental degradation, addressing two critical failure modes in QLED stacks.

Performance data confirm the approach’s impact: the I‑2PACz‑treated Cu:NiO devices reach a peak EQE of 26.95% for green emission, surpassing prior inorganic‑HIL benchmarks by a factor of 3.5. Such efficiency gains translate directly into lower power consumption and brighter panels for consumer electronics, automotive displays, and augmented‑reality optics. The methodology is material‑agnostic, suggesting that similar dipole‑driven SAM treatments could be applied to other metal‑oxide HILs, paving the way for broader adoption of inorganic interfaces in high‑performance optoelectronics.