Quantum dot (QD) light-emitting devices operating in
non-carrier-injection
(NCI) mode have attracted intense interest. Revealing the source of
carriers that support the periodic electroluminescence is important
because there is no injection of carriers from the external electrode.
Electrons/holes generated by well-to-well multiple ionization in adjacent
QDs are generally recognized as the carrier source for electroluminescence,
and the stacked QD layers are necessary. In this work, NCI electroluminescence
(NCI-EL) from monolayer QDs is successfully demonstrated, which cannot
be properly explained by the previously proposed mechanism of multiple
ionization. A working mechanism related to periodic in-well ionization
is proposed, in which electrons tunnel directly from the valence band
of QDs to the conduction band to form free electrons and holes. The
effects of driving voltage amplitude, frequency, and QD size on the
NCI-EL performance are investigated. Finite element simulation is
used to clarify the ionization process. We believe this work can extend
the working mechanism model of NCI-EL from QDs and provide guidance
for promoting QD-based light-emitting device performance.
Noncarrier injection (NCI) operation mode is an emerging driving mode for nanoscale light‐emitting diodes (LEDs) for application in nanopixel light‐emitting displays. However, the luminescence intensity of the NCI‐LED with traditional epitaxial structure is relatively low because of the absence of external carrier injection. Therefore, improving the luminescence intensity by optimizing the epitaxial structure of the LED is an important technical measure. In this work, the tunneling behavior of the NCI‐LED under reverse bias, which plays a key role in increasing the luminescence intensity, is studied through modeling and simulation. The dynamic variation of carrier concentration in each voltage cycle is studied to explore the working process of the NCI‐LED. Results show that the luminescence output of the NCI‐LED is highly sensitive to doping concentrations, and reducing the number of multiquantum wells can increase the probability of interband tunneling so as to improve dramatically the carrier number contributing to luminescence. This simulation work can deepen the understanding of the NCI mode and serve as an important guidance for the rational design of the NCI‐LEDs.
In the human brain, the natural complementary behaviors of synapse connections, which are enhanced and weakened through the participation of astrocytes and microglias, play an important role in the process of training and memory. Even though memristors based on the electrochemical metallization mechanism (ECM) have great potential in realizing electronic synapses (e‐synapses), the lack of complementary ECM e‐synapses has, to a certain extent, hindered the construction of artificial neural networks. In this study, the thermodynamic equilibrium‐nonequilibrium competition (TC) in nanofilaments is meticulously designed by modifying the metal‐ion nanochannels to achieve complementary ECM e‐synapses. The evolution in the morphology of a TC‐induced nanofilament includes a thinning behavior of the nanofilaments caused by electrical stimulation and a coarsening behavior caused by metal‐ion chelation. The TC effect leads to a decrease in the conductance under positive pulse stimulation and to an increase in the conductance while resting, these behaviors being exactly complementary to those of a conventional ECM e‐synapse. Finally, the feasibility of fabricating logic gate circuits with learning capability based on complementary ECM e‐synapses is verified using behavioral‐level modeling. These ECM e‐synapses with complementary functions are expected to be significant to researchers in the field of large neural network systems.
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