ABSTRACT
With pixel miniaturization, the performance of high-resolution quantum dot light-emitting diodes (QLEDs) usually degrades. Considering the dimension of ultrasmall pixels, herein, a barrier architecture based on localized surface plasmon resonance (LSPR) that promotes the radiative recombination of neighboring quantum dots is rationally designed to improve the device performance. Au nanoparticles (NPs) are embedded in an insulating polymer to form a honeycomb-patterned barrier layer via the nanoimprint process. Each pixel fabricated in the void area (average diameter of 1.5 µm) of the barrier layer is surrounded by a number of LSPR-NPs to enhance the luminescence. The resultant green QLEDs with a resolution of 9027 pixels per inch show a maximum external quantum efficiency of 11.1%, a 42.8% enhancement compared to the control device. Additionally, the lifetime of high-resolution QLEDs is obviously improved by the LSPR effect.
ABSTRACT
The photolithographic patterning of fine quantum dot (QD) films is of great significance for the construction of QD optoelectronic device arrays. However, the photolithography methods reported so far either introduce insulating photoresist or manipulate the surface ligands of QDs, each of which has negative effects on device performance. Here, we report a direct photolithography strategy without photoresist and without engineering the QD surface ligands. Through cross-linking of the surrounding semiconductor polymer, QDs are spatially confined to the network frame of the polymer to form high-quality patterns. More importantly, the wrapped polymer incidentally regulates the energy levels of the emitting layer, which is conducive to improving the hole injection capacity while weakening the electron injection level, to achieve balanced injection of carriers. The patterned QD light-emitting diodes (with a pixel size of 1.5 µm) achieve a high external quantum efficiency of 16.25% and a brightness of >1.4 × 105 cd/m2. This work paves the way for efficient high-resolution QD light-emitting devices.
ABSTRACT
Information encryption is an important means to improve the security of anti-counterfeiting labels. At present, it is still challenging to realize an anti-counterfeiting label with multi-function, high security factor, low production cost, and easy detection and identification. Herein, using inkjet and screen printing technology, we construct a multi-dimensional and multi-level dynamic optical anti-counterfeiting label based on instantaneously luminescent quantum dots and long afterglow phosphor, whose color and luminous intensity varied in response to time. Self-assembled quantum dot patterns with intrinsic fingerprint information endow the label with physical unclonable functions (PUFs), and the information encryption level of the label is significantly improved in view of the information variation in the temporal dimension. Furthermore, the convolutional residual neural networks are used to decode the massive information of PUFs, enabling fast and accurate identification of the anti-counterfeit labels.
ABSTRACT
Terahertz plasmon emission is the key to getting terahertz radiation, which has resulted in numerous studies on it. In this paper, we present the results of a theoretical investigation of terahertz plasmon emission by drifting electrons in a grated graphene system driven by an electric field by applying the Boltzmann's equilibrium equation method. The results show that plasmon frequencies from terahertz to infrared are generated by drifting electrons through the interaction between plasmons and electrons. Obvious increase of the plasmon emission strength with the driving electric field can be seen when the electric field is more than a certain strength (e.g. 1.0 kV/cm). The effects of electron density and the grating period on the emission strength of plasmons were also investigated. It was found that terahertz plasmons can be obtained by applying a grating with appropriate period. The plasmon frequencies can be tuned using either the driving electric field or the electron density controlled by the gate voltage or the grating parameters. This work may help to gain insight into graphene plasmonics and be pertinent to the application of graphene-based structures as electrically tunable terahertz plasmonic devices.
