Blue Quantum Dot Light-Emitting Diodes with High Electroluminescent Efficiency

Abstract

High-efficiency blue CdSe/ZnS quantum dots (QDs) have been synthesized for display application with emission peak over 460 nm with the purpose of reducing the harmful effect of short-wavelength light to human eyes. To reach a better charge balance, different size ZnO nanoparticles (NPs) were synthesized and electrical properties of ZnO NPs were analyzed. Quantum dot light-emitting diodes (QLEDs) based on as-prepared blue QDs and optimized ZnO NPs have been successfully fabricated. Using small-size ZnO NPs, we have obtained a maximum current efficiency (CE) of 14.1 cd A and a maximum external quantum efficiency (EQE) of 19.8% for QLEDs with an electroluminescence (EL) peak at 468 nm. To the best of our knowledge, this EQE is the highest value in comparison to the previous reports. The CIE 1931 color coordinates (0.136, 0.078) of this device are quite close to the standard (0.14, 0.08) of National Television System Committee (NTSC) 1953. The color saturation blue QLEDs show great promise for use in next-generation full-color displays.

The influence of the hole transport layers on the performance of blue and color tunable quantum dot light‐emitting diodes

“…With regard to the current density–voltage (J–V) characteristics, devices with TFB exhibit significantly larger current density; for example, at a driving voltage of 6 V, the TFB‐devices exhibit a current density of 318.7 mA/cm 2 , which is about threefold higher than 76.4 mA/cm 2 of the PVK‐devices. Although the HOMO level of TFB (5.3 eV) is lower than 5.8 eV of PVK, the hole mobility of TFB (5 × 10 −3 cm 2 V −1 s −1 ) is three orders of magnitude higher than 2.5 × 10 −6 cm 2 V −1 s −1 of PVK, and thus with the more conductive TFB HTL, the devices exhibit significantly larger current density. With the TFB HTL, the charge injection seems to be quite efficient, but the devices exhibit a relatively low EQE of 2.8%, which is twice lower than 8.6% of the PVK‐devices.…”

“…With the rapid development of QD materials and device structures, the performances of red and green devices have been substantially improved; for example, the external quantum efficiencies (EQE) of red and green QLEDs have reached 20.5% and 21% and they have been lately improved from 23.1% to 27.6% by using tandem structures, which are very close to those of organic LEDs (OLEDs) . And blue QLEDs with EQE of 19.8% and 21.4% have also been reported very recently. However, compared with red and green devices, the efficiency and stability of blue QLEDs remain relatively poor; thus, there is still substantial room for further improvement.…”

Recent advances and prospects toward blue perovskite materials and light‐emitting diodes

“…The images are phosphors, OLEDs, PLEDs, GaN LEDs Cd-based QLEDs and perovskite LEDs (bottom) and the corresponding material structure of phosphors (BAM), organic small molecule (TDPVBi, 2, 5, 2 0 , 5 0 -tetrakis (2, 2-diphenylvinyl) biphenyl), organic polymer (PFO, poly (9,9-dioctylfluorene)), GaN, core/shell QDs and perovskites (top) from left to right. 5,[8][9][10][11][12][13][14][15][16][17][18][19] the A-, B-, and X-site ions. Then, we demonstrate recent strategies for highly efficient blue perovskite materials and devices, and analyze possible causes of poor blue device performances.…”

Progress of display performances: AR, VR, QLED, and OLED

“…Recently, > 30% EQE was reported through shell growth control and modification of the surface ligands of the red-emitting Cd-based QDs [45]. As shown in Figure 1 and Table 5, the maximum EQEs of red-, green-, and blue-emitting QLEDs reached 30.9, 25.04, and 19.5%, respectively [45,51,54].…”