An electroluminescent quantum-dot light-emitting diode (QLED) device and a micro QLED device array with a top-emitting structure were demonstrated in this study. The QLED device was fabricated in the normal structure of [ITO/Ag/ITO anode]/PEDOT:PSS/PVK/QDs/[ZnO nanoparticles]/Ag/MoO3, in which the semi-transparent MoO3-capped Ag cathode and the reflective ITO/metal/ITO (IMI) anode were designed to form an optical microcavity. Compared with conventional bottom-emitting QLED, the microcavity-based top-emitting QLED possessed enhanced optical properties, e.g., ~500% luminance, ~300% current efficiency, and a narrower bandwidth. A 1.49 inch micro QLED panel with 86,400 top-emitting QLED devices in two different sizes (17 × 78 μm2 and 74 × 40.5 μm2) on a low-temperature polysilicon (LTPS) backplane was also fabricated, demonstrating the top-emitting QLED with microcavity as a promising structure in future micro display applications.

Feasible electroluminescent quantum dot light-emitting diodes (QLEDs) fabricated by a single spin coating of dual monochromatic alloyed quantum dots (QDs) were investigated and compared in this study. All the devices were fabricated in the same structure of indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)] (ITO/PEDOT:PSS/TFB)/mixed-QDs/ZnO/Al with single mixed-QDs emissive layer, which possessed controllable dual emission spectra and provided flexibility and applicability in practical applications. By selecting two of blue ZnCdS, green ZnCdSeS, yellow core/shell ZnCdSeS/ZnS, and red core/shell ZnCdSeS/ZnSeS QDs with suitable surface modifications to ensure similar surface chemistry, devices could exhibit dual emission peaks with various color compositions such as deep yellow, red-pink, ocean blue, and pure white light with luminance as high as 6970 cd/m 2 , and the color coordinate could be feasibly adjusted by either applied voltages or QD weight ratio. It was also observed that the similarity of QD chemical composition appeared to influence the electroluminescent wavelength, which was ascribed to a local like−like aggregation in the mixed-QD film in the devices.

diode (OLED), unfortunately, they have a relatively large volume, low contrast, [8] and slow response time. [9] Self-emitting electroluminescent (EL) QD applied for displays without any backlighting is considered to be a next-generation QD display. It has a similar device structure to that of OLED, except that the emitting layer is made of EL QD film, which exhibits much better optical characteristics such as emission bandwidth or color gamut, carrier mobility [9] and applicability in flexible displays. [10] Recent studies of EL QLED have driven a progress of the device external quantum efficiency (EQE) more than 20% via balancing injection carrier, [11][12][13][14][15] modifying QD structure, [16][17][18][19][20] and introducing a tandem device structure. [21][22][23] Meanwhile, the durability of QLEDs has been also much improved. [16,18,20] Furthermore, many QD printing techniques including inkjet printing, [24,25] transfer printing, [26,27] and photolithography process [28][29][30][31] have been developed to realize the full-color pixelation of QLED for display applications.To display an image, on the other hand, the light-emitting devices or pixels must be driven individually with appropriate wiring electrodes and driver boards. For example, passive matrix (PM) [32] or active matrix (AM) [33,34] addressing system, are generally employed to control the EL of every pixel. In a PM-based display, a grid of vertical and horizontal electrodes is used to control the emitting pixels. A scanning voltage is utilized to light the selected pixels up in each row, so an image line along with frame can be generated and perceived by the human eye because of the vision persistence. When more frames, for example, 30-60 frames, are sequentially generated by driving selected emitting devices in a short time interval, a dynamic image is then displayed. In a AM-based display, a set of thin film transistors (TFT) and capacitors is used to drive every single pixel, having a better current control over the pixels and more suiting to larger-size and high-resolution displays. [35,36] However, the TFT addressing system is much more complicated and he fabrication process is very expensive. In terms of small panel applications such as medical electronics, automotive, and wearable displays, PM-addressing displays like PM-OLED are still a main stream. [37,38] Compared with PM-OLED, PM-QLED have advantages of a wider color gamut, lower material cost and more feasible large-area fabrication process. So PM-QLED has been considered one of the promising displays in the future.

See‐through double‐side‐emitting electroluminescent quantum‐dot light‐emitting‐diodes (QLEDs) with highly transparent tri‐layer MoO3/Ag:Cu/MoO3 electrode is demonstrated in this study. The tri‐layer MoO3/Ag: Cu/MoO3 electrode is prepared by a thermal co‐evaporation process, in which MoO3 is utilized as both a seed layer and a capping layer. This tri‐layer structure improves the transmittance as high as ≈88% and ≈86% for pure Ag and Ag:Cu at 550 nm, respectively. It is also found that minor Cu doping significantly improves the thermal stability and sheet resistance of Ag film. With the see‐through tri‐layer film as a device cathode, transparent double‐side‐emitting green QLED exhibits remarkable high brightness of 225, 500 cd m−2, the current efficiency of 58.68 cd A−1, the external quantum yield of 16.70%, and transmittance of 77% at 550 nm without any additional anti‐reflection coating.

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