Dipole Engineering through the Orientation of Interface Molecules for Efficient InP Quantum Dot Light-Emitting Diodes

Seungjin Lee, So Min Park, Eui Dae Jung, Tong Zhu, Joao M. Pina, Husna Anwar, Feng Yi Wu, Guan Lin Chen, Yitong Dong, Teng Cui, Mingyang Wei, Koen Bertens, Ya Kun Wang, Bin Chen, Tobin Filleter, Sung Fu Hung, Yu Ho Won, Kwang Hee Kim, Sjoerd Hoogland, Edward H. Sargent*


研究成果: Article同行評審

2 引文 斯高帕斯(Scopus)


InP-based quantum dot (QD) light-emitting diodes (QLEDs) provide a heavy-metal-free route to size-tuned LEDs having high efficiency. The stability of QLEDs may be enhanced by replacing organic hole-injection layers (HILs) with inorganic layers. However, inorganic HILs reported to date suffer from inefficient hole injection, the result of their shallow work functions. Here, we investigate the tuning of the work function of nickel oxide (NiOx) HILs using self-assembled molecules (SAMs). Density functional theory simulations and near-edge X-ray absorption fine structure put a particular focus onto the molecular orientation of the SAMs in tuning the work function of the NiOx HIL. We find that orientation plays an even stronger role than does the underlying molecular dipole itself: SAMs having the strongest electron-withdrawing nitro group (NO2), despite having a high intrinsic dipole, show limited work function tuning, something we assign to their orientation parallel to the NiOx surface. We further find that the NO2 group─which delocalizes electrons over the molecule by resonance─induces a deep lowest unoccupied molecular orbital level that accepts electrons from QDs, producing luminescence quenching. In contrast, SAMs containing a trifluoromethyl group exhibit an angled orientation relative to the NiOx surface, better activating hole injection into the active layer without inducing luminescence quenching. We report an external quantum efficiency (EQE) of 18.8%─the highest EQE among inorganic HIL-based QLEDs (including Cd-based QDs)─in InP QLEDs employing inorganic HILs.

頁(從 - 到)20923-20930
期刊Journal of the American Chemical Society
出版狀態Published - 16 11月 2022


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