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.
The vertical field-effect phototransistor (VFEPT) has received great attention because of its large current density and the low operation voltage required to achieve the desirable photodetector performance. The design of the device architecture and selection of the fabrication method play a vital role in obtaining a high-performance phototransistor that can be manufactured at a scale. Here, we present a highly efficient, all-solution-processable VFEPT based on PbSe quantum dots, in which the charge generation and charge transportation layers (CGL and CTL) are separated by a porous silver nanowire electrode and an ionic gel layer, and the CG efficiency and CT efficiency can be modified independently for near-infrared photodetection. The phototransistor performance is greatly enhanced by a field effect from the CGL that facilitates charge injection into the CTL. The maximum responsivity and the detectivity of the photodetector are 28 A W −1 at −0.75 V SD and 1.3 × 10 13 Jones at 0.5 V SD under a low bias voltage of 1 V GS using 1064 nm illumination.
CdSe/ZnS quantum dots (QDs) have attracted great consideration from investigators owing to their excellent photo-physical characteristics and application in quantum dot light-emitting diodes (QD-LEDs). The CdSe/ZnS-based inverted QD-LEDs structure uses high-quality semiconductors electron transport layers (ETLs), a multilayered hole transporting layers (HTLs). In QD-LED, designing a device structure with a minimum energy barrier between adjacent layers is very important to achieve high efficiency. A high mobility polymer of poly (9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine (TFB) was doped with 4,4′-bis-(carbazole-9-yl) biphenyl (CBP) with deep energy level to produce composite TFB:CBP holes to solve energy mismatch (HTL). In addition, we also improved the QD-LED device structure by using zinc tin oxide (ZTO) as ETL to improve device efficiency. The device turn-on voltage Vt (1 cd m−2) with ZTO ETL reduced from 2.4 V to 1.9 V significantly. Furthermore, invert structure devices exhibit luminance of 4296 cd m−2, current-efficiency (CE) of 7.36 cd A−1, and external-quantum efficiency (EQE) of 3.97%. For the QD-LED based on ZTO, the device efficiency is improved by 1.7 times.
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