Engineering Architecture of Quantum Dot-Based Light-Emitting Diode for High Device Performance with Double-Sided Emission Fabricated by Nonvacuum Technique

The CdSe/ZnS quantum dots (QDs) have drawn the attention of the researchers due to their superior photophysical properties and their applications in QD-based light-emitting diodes (QLEDs). The conventional CdSe/ZnS-based QLED uses a highly conductive electron-transport layer, low-mobility hole-transporting layers (HTLs), and a vacuum-deposited opaque metal electrode at the top. This structure renders unbalanced charge injection into the emissive layer and also allows the device to emit light only at the bottom side, which affects the device output luminance and stability. Moreover, in the vacuum-deposition technique, the fabrication process is more complex, expensive, and time-consuming. To address all these issues, we fabricated an all-solution processable double-sided emitting QLED by a nonvacuum technique using high mobility multi-HTLs with a cascade structure, an insulating layer, and a transparent silver nanowire (AgNW) electrode for balanced charge injection for obtaining higher luminance at the top-side AgNW electrode. The as-fabricated QLED exhibited a very low turn-on voltage and high luminance of 2.2 V and 41,010 cd m–2, respectively. The QLED has also shown a high current efficiency of 15.2 cd A–1, a luminous efficiency of 16.2 lm W–1, and an external quantum efficiency of 8.2% at the top-side. These results indicate that the double-sided emitting QLED device opens up a pathway for designing next-generation lighting and display devices.