Deuterated Molecular Vibration Locking in Self-Assembled Monolayers Enables Positive Aging-Free SnO2-Based QLEDs With Over 30% External Quantum Efficiency

The development of efficient and stable hole injection layers (HILs) remains a critical challenge for high-performance quantum-dot light-emitting diodes (QLEDs), as the conventional PEDOT:PSS suffers from inherent acidity and hygroscopicity. Herein, we demonstrate a novel strategy of molecular vibration engineering by employing deuterated self-assembled monolayers (SAMs) as an efficient alternative. The designed deuterated molecular backbone (Ph-4PACzd10), featuring extended conjugated structures, not only delivers an enhanced molecular dipole moment to significantly deepen the work function of ITO, but also effectively suppresses high-frequency C─H stretching vibrations through isotopic substitution, which promotes highly ordered molecular packing and superior film morphology, thereby minimizing interfacial energetic disorder and non-radiative recombination losses. As a result, SnO 2 -based QLEDs utilizing Ph-4PACzd10 achieve a record-breaking external quantum efficiency (EQE) of 30.87%, markedly surpassing that of the conventional PEDOT:PSS-based device (24.03%). Furthermore, the hydrophobic nature of the deuterated SAMs endows the devices with exceptional shelf and operational stability. Notably, the QLED device demonstrated excellent efficiency roll-off characteristics, maintaining an EQE exceeding 20% at an ultra-high luminance of 250 000 cd m −2 , with no positive aging effect observed. This work illustrates that isotopic engineering of molecular vibrations provides a compelling pathway to tailor interfacial energetics and advance the design principles for next-generation QLEDs.