Patterned‐Bank‐Free Electroluminescent Quantum Dot Emitting Array for Passive‐Matrix QLED Display

Abstract

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.

Cubic- and Hexagonal-Phase MgZnO Nanoparticles for Electron Transport Layers in Electroluminescent Quantum-Dot Light-Emitting Diodes

“…Effective transport of electrons in MZO enables WZ-MZO- and ZB-MZO-based devices to permanently lower the turn-on voltage ( V on ) to 6.7 and 6.3 V, respectively; it is reduced compared to the ZnO-based device with a V on of 7.6 V, as shown in Figure a. It has been observed that the high V on could potentially be attributed to the thick-shell QDs. , Previous studies have confirmed that EL QLEDs composed of ZnCdSeS alloy QDs with a thicker shell exhibit notably elevated current density and brightness in comparison to conventional core/shell QDs. ,, ZB-MZO- and WZ-MZO-based EL devices have maximal brightness values of 155,100 and 123,500 cd/m 2 , respectively, significantly greater than that of the ZnO-based device (22,030 cd/m 2 ). The maximum CE (CE max ) of the ZnO-based device is ∼4.9 cd/A.…”

“…Fabrication of devices was carried out under atmospheric conditions, except that the cathode layer was deposited in the vacuum. 15 QLED devices with the structure ITO/ PEDOT/HTL/G-QDs/ETL/Al were fabricated using the same process conditions, but various types of ETLs and HTLs were used to investigate the device characteristics. Deionized water, acetone, IPA, and UV−ozone were used to clean the ITO substrates (sheet resistance, ∼20 Ω/sq).…”

“…42,43 Previous studies have confirmed that EL QLEDs composed of ZnCdSeS alloy QDs with a thicker shell exhibit notably elevated current density and brightness in comparison to conventional core/shell QDs. 15,16,44 ZB-MZOand WZ-MZO-based EL devices have maximal brightness values of 155,100 and 123,500 cd/m 2 , respectively, significantly greater than that of the ZnO-based device (22,030 cd/ m 2 ). The maximum CE (CE max ) of the ZnO-based device is ∼4.9 cd/A.…”

Top-Emitting Active-Matrix Quantum Dot Light-Emitting Diode Array with Optical Microcavity for Micro QLED Display

“…A cover glass and the UV-curable resin were used to encapsulate the device. The synthesis of ZnO nanocrystals was described in our previous paper [ 41 ]. For comparison, devices prepared with two other alloyed ZnCdSeS QDs with different shell thicknesses (G-QD-2/1.1 nm shell thickness/wavelength 523 nm/FWHM 20.5 nm/PLQY 65% and G-QD-3/1.6 nm shell thickness/wavelength 521 nm/FWHM 17.7 nm) were also fabricated using the same processes and parameters.…”

Chromaticity-Tunable All-Inorganic Color Converters Fabricated by 3D Printing for Modular Plant Growth Lighting Devices

“…Natural light is seriously affected by the alternation of day and night, seasons, latitude, and weather conditions. , The regulation of artificial light has become an inevitable choice for improving the efficiency of agricultural production according to the rhythm of the growth and development of plants . At present, light-emitting diodes (LEDs) have become a new generation of lighting sources that are suitable for modern intelligent agricultural production due to their high brightness, energy efficiency, environmental protection, low voltage, adjustable wavelength, etc. − However, as a result of the poor chemical stability and thermal conductivity of the organic encapsulation resin in commercial LEDs, the aging and yellowing of resin and the degradation of the performance of the phosphor easily occur under long-term irradiation of high-power chips or in a high-temperature environment, resulting in light failure, color deviation, and short actual service lives of LEDs. In addition, the narrow emission bandwidth of commercial plant lighting LEDs cannot meet the requirements of the growth and development rhythms for different plants.…”