An ideal anti-counterfeiting technique has to be inexpensive, mass-producible, nondestructive, unclonable and convenient for authentication. Although many anti-counterfeiting technologies have been developed, very few of them fulfill all the above requirements. Here we report a non-destructive, inkjet-printable, artificial intelligence (AI)-decodable and unclonable security label. The stochastic pinning points at the three-phase contact line of the ink droplets is crucial for the successful inkjet printing of the unclonable security labels. Upon the solvent evaporation, the three-phase contact lines are pinned around the pinning points, where the quantum dots in the ink droplets deposited on, forming physically unclonable flower-like patterns. By utilizing the RGB emission quantum dots, full-color fluorescence security labels can be produced. A convenient and reliable AI-based authentication strategy is developed, allowing for the fast authentication of the covert, unclonable flower-like dot patterns with different sharpness, brightness, rotations, amplifications and the mixture of these parameters.

Since the colloidal quantum dots (QDs) started being utilized as novel fluorescent materials in early 1980s, [1][2][3] great efforts and rapid progresses have been made during the last 30 years in QD-based solid-state lighting and flat-panel display technologies. [4][5][6][7] A principal character of QDs is the quantum confinement induced tunability of their emission color (from The balance injection of holes and electrons into a thin emissive quantum dot (QD) layer for efficient radiative recombination is critical to the color purity, stability, and efficiency of the QD-based light-emitting diodes (QD-LEDs).Due to the difficulty of charge injection into wide band gap blue QD layer, the performance of blue QD-LED is obviously inferior to the green and red counterparts. Here, high-performance ZnCdS/ZnS graded core/shell-based blue QD-LEDs with partial oxidized aluminum cathode (Al:Al 2 O 3 ) via simple autoxidation are demonstrated. There is no any additional electron transport layer/hole transport layer involved in the device, which guarantees the color purity and simplifies the fabrication processes. Furthermore, the Al:Al 2 O 3 cathode greatly enhances the charge injection and exciton recombination, rendering significant improvement in luminance and current efficiency compared with the control devices with Al or Alq3/Al electrodes. A record luminance of over 13 000 cd m −2 has been achieved for blue QD-LEDs with Al:Al 2 O 3 cathode. The findings of this study indicate that this simply processed and easily controlled autoxidation procedure is a promising strategy to achieve high-performance blue QD-LEDs.

Colloidal quantum dots (QDs) have attracted great attention due to their high quantum efficiency, full color tunability, narrow emission bandwidth, high chemical stability, and High performance and super stable all-inorganic full-color quantum dot lightemitting diodes (QLEDs) are constructed by adopting solution-processed Mgdoped NiO x (Mg-NiO x) nanoparticles as hole transport layer (HTL) and Al-doped ZnO (AZO) as electron transport layer (ETL). Mg-NiO x nanoparticles possess the advantages of low-temperature solution processability, intrinsic stability, and controllable electronic properties. UV-ozone (UVO) treatment is applied to the Mg-NiO x film to modulate its surface composition. By carefully controlling the UVO treating time, favorable energy levels can be achieved to minimize the energy barrier for hole injection. At the cathode side, Al-doping can reduce the conductivity of ZnO ETL and decrease the interface charge transfer, effectively, thus leading to more balanced charge injection and consequent high luminance and efficiency. The maximum luminance and EQE can reach as high as 38 444 cd m −2 and 5.09% for R-QLEDs, 177 825 cd m −2 and 10.1% for G-QLEDs, and 3103 cd m −2 and 2.19% for B-QLEDs. The luminance values are the highest ever reported for all-inorganic QLEDs. Furthermore, the all-inorganic devices show much better resistance to water and oxygen existing in air. The results show that the ion-doped NiO x and AZO nanoparticles would facilitate the design and development of highly efficient and super stable QLEDs.

Colloidal quantum dots light‐emitting diodes (QD‐LEDs) have been investigated for several decades. Compared with their green and red counterparts, the hole injection is more difficult for blue QDs due to their large optical band gap and relatively low highest occupied molecular orbital level. High‐performance blue QD‐LEDs are demonstrated by inserting a thin deoxyribonucleic acid (DNA) buffer layer between hole transport layer and ZnCdS/ZnS core/shell QDs layer. This DNA buffer layer can effectively enhance the hole injection efficiency, meanwhile its high lowest unoccupied molecular orbital level can help the injected electrons to be confined in the emitting layer, thus ensuring the charge balance in the QDs layer and an excellent recombination efficiency. After utilizing DNA as buffer layer, the maximum luminance is significantly increased from 10 218 to 16 655 cd m−2 and the external quantum efficiency is increased from 4.39% to 5.65%. These devices provide a saturated blue emission with emission peak located at 462 nm and full width at half maximum of 21 nm. This saturated blue emission makes it suitable for commercial applications. The results indicate that DNA is a promising material for regulating charge balance in the emitting layer for manufacturing high performance QD‐LEDs.

extensive attention in the field of optoelectronics, such as light emitting diodes (LEDs), photovoltaics, photodetectors, and lasers. [1][2][3] Among these, quantum dot LEDs (QLEDs) have attracted wide attention for their potential applications in thinfilm display and large-area lighting. [4] Since the QLEDs was first report in 1994, significant improvement has been achieved in both luminance and efficiency owing to the rapid development of QD materials and device architectures, [5][6][7] which foreshadows the commercialization of QLEDs in the future. [4,8] Among the various QD materials, Cd-based II-VI semiconductor QDs have relatively simple synthetic route [9] and highly visible-luminescent property, [10] making them the most attractive QDs for high-performance devices.In typical QLED geometry, the QDs emitting layer is sandwiched between the electron-transporting layer (ETL) and the hole-transporting layer (HTL). Early QLEDs drew a large amount of organic ETL and HTL materials from organic LEDs (OLED), [1,11] but were somehow restricted by them. Organic transporting materials generally suffer from low thermal stability and are easily eroded by oxygen and water, which deteriorates device performance. Besides, small-molecular organic layers are usually deposited through physical vapor deposition method, which increases the expense of production. Therefore, semiconducting metal oxides represented by ZnO, TiO 2 , and SnO 2 are gradually introduced in QLEDs as ETL. Metal oxides show superior physical and chemical stability and electronic conductivity in comparison with their organic counterparts. A wide variety of metal oxides can meet the requirements for energy band alignment with the neighboring layers. These properties enable metal oxides to be applicable for QLEDs as charge transport layer.People's understanding toward metal oxide ETL has experienced transfer over time. At first, the high free-carrier density in metal oxide crystal was thought to intensely quench the excitons formed in QDs. [12] Therefore, various methods were applied to fabricate amorphous metal oxide ETL, including zinc tin oxide (ZTO) deposited from magnetron sputtering [13] and sol-gel-made TiO 2 . [14] However, researchers then discovered the generally fairly low electron mobility in amorphous metal oxide (up to 4 orders of magnitude lower than the corresponding The balance of hole-electron injection is always a vital factor for the luminance, efficiency and working lifetime of quantum-dot light-emitting diodes (QLEDs), especially blue QLEDs. However, currently most approaches proposed to solve this issue involve tedious optimization of device architecture or material composition. Here, high-performance blue QLEDs are reported based on CdZnS/ZnS quantum-dot (QDs) by utilizing ZnO nanoparticles (NPs) and Al:Al 2 O 3 as electron-transporting layer (ETL) and cathode materials, respectively. The effect of post-annealing temperature on the trap state density in ZnO NPs and the related mechanisms are investigated through optical and photoelect...