Abstract
We report herein an all-inorganic quantum dot light emitting diode (QLED) where an optically active layer of crystalline silicon (Si) is mounted. The prototype Si-QLED has an inverted device architecture of ITO/ZnO/QD/WO3/Al multilayer, which was prepared by a facile solution process. The QLED shows a red electroluminescence, an external quantum efficiency (EQE) of 0.25%, and luminance of 1400 cd/m2. The device performance stability has been investigated when the device faces different humidity conditions without any encapsulation. The advantage of using all inorganic layers is reflected in stable EQE even after prolonged exposure to harsh conditions.
Highlights
Silicon quantum dots (Si QDs), promising for applications in fluorescence biomarkers because of their low cytotoxicity [1,2,3], have recently shown improved device performance for prototype light emitting diodes (QLEDs) [4,5,6,7,8]
With an electron affinity of 4.3 eV and an ionization potential of 7.6 eV [25], the zinc oxide (ZnO) electron injection layer (EIL)/electron transportation layer (ETL) worked for efficient electron injection from the Indium tin oxide (ITO) electrode into an active layer of Si QDs
The layer of ZnO worked for confinement of holes within the active layer because of the valence band offset at the ZnO/QD interface
Summary
Silicon quantum dots (Si QDs), promising for applications in fluorescence biomarkers because of their low cytotoxicity [1,2,3], have recently shown improved device performance for prototype light emitting diodes (QLEDs) [4,5,6,7,8]. We expect a dramatically improved device performance for a current-driven LED with Si. QDs because external quantum efficiency (EQE) should be dominated by recombination rate between electrons and holes injected from electrodes. The important step is the development of an advanced Si-QLED, in addition to achieving an optimized optical performance in terms of low turn-on voltage, high EQE, strong brightness, Gaussian-shaped electroluminescence (EL) spectra, narrow emission band tunable over a wide range from visible to near-infrared (NIR). For Si-QLEDs, polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) and poly TPD serve as the HTL/HIL, while
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