Improved Ink-Jet-Printed CdSe Quantum Dot Light-Emitting Diodes with Minimized Hole Transport Layer Erosion

Abstract

Ink-jet printing is a promising deposition technology, which is capable of large-area fabrication and mask-free patterning. For ink-jet-printed quantum dot (QD) light-emitting diodes (LEDs), the QDs are commonly dissolved in a mixture of solvent and thickener ink system. However, the hole transport layer could be eroded by this QD ink, leading to a rough surface morphology and resulting in the leakage of carriers and low device performance. This phenomenon was first and directly observed by using an atomic force microscope and a cross-sectional scanning electron microscope. We, therefore, redesigned the annealing process of the hole transport layer to achieve an optimized smooth surface with a reduced number of defects for ink-jet-printed QD LEDs (QLEDs). Optimized morphology brings back a maximum luminance of over 30,000 cd/m2 and an external quantum efficiency of 7.52% for the ink-jet-printed red QLEDs using CdSe QDs, which are comparable to those of the spin-coated device. Moreover, the operation lifetime of the ink-jet-printed device is also enhanced by the restored surface morphology. An enhanced T 50 lifetime of the ink-jet-printed device at 1000 cd/m2 is improved from 26 to 127 h, which converted to a long T 50 lifetime of 8013 h, when operated at 100 cd/m2.

Bright Red-Emitting Ca3LuAl3B4O15:Ce3+,Sm3+ Phosphors with High Thermal Stability for Elevating the Color Rendering of Near-Ultraviolet-Based White-Light-Emitting Diodes

“…To address the challenges regarding the light sources, new white-light-emitting diodes (WLEDs) have been one of the hot research concerns, with much attraction. , Lanthanide ions activated by inorganic phosphors have attracted a lot of attention owing to their importance in biological imaging, environmental friendliness, energy saving, long life, and so on. − The attempt to develop WLEDs by mixing a yellow-emitting phosphor with a blue InGaN chip remained controversial due to the red spectral deficiency. ,, Therefore, an alternative approach was used to make a near-ultraviolet (UV) LED chip with tricolor-emitting phosphors (340–410 nm). , The fixing of the red component, such as red emission from quantum dots or nitride materials, is an alternative method for improving the color-rending index (CRI). , However, some drawbacks associated with nitride phosphors such as manufacturing costs and unhealthy Cd component restrict their practical implementation. , The subject of generating energy transfer (ET)-based materials for WLEDs with high thermal stability and low correlated color temperature (CCT) has drawn considerable attention. − …”

Improvement of the efficiency and stability of inkjet‐printed green quantum dot light‐emitting diodes by controlling the extra shell of quantum dot

“…, where Q in , Q trap , and Q r refer to the injected carriers for the charging process, trapped, and recombined carriers, respectively. 47 The B-QD device exhibits the lowest turn-on voltage (1.9 V) compared to A -and C-QD devices, indicating that it is more efficient for electron/hole injection into the emitting layer for B-device. The C À V curves at higher voltage demonstrate the carrier dynamics of accumulation and recombination.…”

“…To further study the effect of the shell thickness on the carrier dynamics in the IJP devices, the capacitance–voltage characteristics of A‐, B‐, C‐QD devices were analyzed (Figure 6A). The device capacitance is calculated by , where Q in , Q trap , and Q r refer to the injected carriers for the charging process, trapped, and recombined carriers, respectively 47 . The B‐QD device exhibits the lowest turn‐on voltage (1.9 V) compared to A ‐and C‐QD devices, indicating that it is more efficient for electron/hole injection into the emitting layer for B‐device.…”

Dual-Mode Flexible Sensor Based on PVDF/MXene Nanosheet/Reduced Graphene Oxide Composites for Electronic Skin

“…Through the motion of the substrate, a pattern or thin film with micro/nano structures can be prepared. Therefore, the method can be used to fabricate a flexible pressure/strain sensor [ 41 , 42 , 43 , 44 ].…”