Exploring the temperature-dependent electroluminescence (EL) properties of quantum dots (QDs) is not only critical for the fundamental understanding of charge recombination processes in quantum dot light-emitting diodes (QLEDs) but also important to expand their particular applications at cryogenic temperatures. Herein, the temperature-dependent EL properties of typical CdSe/ZnS core/shell QDs were systematically studied for both the standard and inverted QLEDs in the temperature range of 100–300 K. It was found that EL intensity and efficiency were gradually enhanced and exhibited a pronounced blue shifting in EL spectra with the decrease in temperature. We demonstrated that temperature-dependent EL behaviors mainly originated from the inherent properties of QDs, while the different device structures could induce some fine temperature-dependent behaviors on this basis. Moreover, the effective Joule heat dissipation at low temperatures protects the charge transport and QD layers from thermal decomposition and damage, which prolongs the operational lifetime of devices.
A reliable encapsulation technology with scalability
and flexibility
is urgently needed for electroluminescence devices. Here, we developed
a simple, robust, low-cost, and scalable flexible lamination encapsulation
strategy with quantum-dot light-emitting diodes (QLEDs) as the model
devices. Multilayered Parafilm combining with calcium oxide buffer
was used for the lamination encapsulation. We successfully demonstrated
that such a Parafilm Lami encapsulation (PLE) not only allowed excellent
protection for QLEDs in air but endowed QLED outstanding waterproof
performance. As a result, highly efficient and stable flexible waterproof
QLEDs were realized based on this PLE, exhibiting maximum external
quantum efficiency of ∼8% and long half-luminescence lifetime
of over 1.5 h in water. We believe that there are not any obstacles
to extending this encapsulation technology to other flexible flat-panel
devices, such as organic/perovskite light-emitting diodes.
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