In the study of hybrid quantum dot light-emitting diodes (QLEDs), even for state-of-the-art achievement, there still exists a long-standing charge balance problem, i.e., sufficient electron injection versus inefficient hole injection due to the large valence band offset of quantum dots (QDs) with respect to the adjacent carrier transport layer. Here the dedicated design and synthesis of high luminescence Zn 1−x Cd x Se/ZnSe/ZnS QDs is reported by precisely controlled shell growth, which have matched energy level with the adjacent hole transport layer in QLEDs. As emitters, such Zn 1−x Cd x Se-based QLEDs exhibit peak external quantum efficiencies (EQE) of up to 30.9%, maximum brightness of over 334 000 cd m −2 , very low efficiency roll-off at high current density (EQE ≈25% @ current density of 150 mA cm −2 ), and operational lifetime extended to ≈1 800 000 h at 100 cd m −2 . These extraordinary performances make this work the best among all solution-processed QLEDs reported in literature so far by achieving simultaneously high luminescence and balanced charge injection. These major advances are attributed to the combination of an intermediate ZnSe layer with an ultrathin ZnS outer layer as the shell materials and surface modification with 2-ethylhexane-1-thiol, which can dramatically improve hole injection efficiency and thus lead to more balanced charge injection.
In article number 1808377, Huaibin Shen, Lin Song Li, and co‐workers fabricate light‐emitting diodes with an external quantum efficiency >30% by exploiting Zn1−xCdxSe core/shell quantum dots with ZnSe as the intermediate layer and ultrathin ZnS. The maximum brightness achieved is up to 334 000 cd m−2, and the operational lifetime is extended to ≈1 800 000 h at 100 cd m−2.
Quantum dot light‐emitting diodes (QLEDs) are considered to be the candidate light sources with the most potential for applications in displays. Recent advances in luminance, external quantum efficiency (EQE), and even the operation lifetime of QLEDs have already satisfied the requirements for low‐light‐level displays. However, the short operation lifetime under high brightness limits the application of QLEDs for outdoor displays and lightings. Here, demonstrated are green QLEDs with a T95 operation lifetime reaching up to 2500 h at high brightness (1000 cd m−2) with a high peak EQE of 23.9%, current efficiency of 100.5 cd A−1, and low efficiency roll‐off at high current. Both the EQE and lifetime of the QLEDs are superior to those reported to date for all solution‐processed green QLEDs. These major advances are qualitatively attributed to the use of a shell‐tailoring strategy for producing compositional graded CdZnSe/ZnSe/ZnSeS/ZnS quantum dots with a high photoluminescence quantum yield, suppressed nonradiative Förster resonant energy transfer and Auger recombination, and favorable valence band alignment for enhanced hole injection. Collectively, this work represents a huge step forward in eventually realizing QLEDs for high‐brightness display and lighting applications.
One reported mechanism for morphine activation of dopamine (DA) neurons of the ventral tegmental area (VTA) is the disinhibition model of VTA-DA neurons. Morphine inhibits GABA inhibitory neurons, which shifts the balance between inhibitory and excitatory input to VTA-DA neurons in favor of excitation and then leads to VTA-DA neuron excitation. However, it is not known whether morphine has an additional strengthening effect on excitatory input. Our results suggest that glutamatergic input to VTA-DA neurons is inhibited by GABAergic interneurons via GABAB receptors and that morphine promotes presynaptic glutamate release by removing this inhibition. We also studied the contribution of the morphine-induced disinhibitory effect on the presynaptic glutamate release to the overall excitatory effect of morphine on VTA-DA neurons and related behavior. Our results suggest that the disinhibitory action of morphine on presynaptic glutamate release might be the main mechanism for morphine-induced increase in VTA-DA neuron firing and related behaviors.DOI:
http://dx.doi.org/10.7554/eLife.09275.001
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