Stability of Quantum-Dot Light Emitting Diodes with Alkali Metal Carbonates Blending in Mg Doped ZnO Electron Transport Layer

Abstract

We report here the fabrication of highly efficient and long-lasting quantum-dot light emitting diodes (QLEDs) by blending various alkali metal carbonate in magnesium (Mg) doped zinc oxide (ZnO) (MZO) electron transport layer (ETL). Alkali metal carbonates blending in MZO, X2CO3:MZO, control the band-gap, electrical properties, and thermal stability. This can therefore enhance the operational lifetime of QLEDs. It is found that the conductivity of X2CO3:MZO film can be controlled and the thermal stability of ETLs could be improved by X2CO3 blending in MZO. The inverted red QLEDs (R-QLEDs) with Cs2CO3:MZO, Rb2CO3:MZO, and K2CO3:MZO ETLs exhibited the operational lifetime of 407 h for the R-QLEDs with Cs2CO3:MZO, 620 h with Rb2CO3:MZO and 94 h with K2CO3:MZO ETLs at T95 with the initial luminance of 1000 cd/m2. Note that all red QLEDs showed the high brightness over 150,000 cd/m2 But, the R-QLEDs with Na2CO3:MZO and Li2CO3:MZO ETLs exhibited shorter operational lifetime and poor brightness than the R-QLED with pristine MZO ETL.

Finely Controlled Synthesis of Zn1–xMgxO Nanoparticles with Uniform Size Distribution Used as Electron Transport Materials for Red QLEDs

“…14 Indeed, QLEDs using ZnO NPs doped with the Mg ion as the ETL have achieved remarkable success and have reached efficiencies as high as 20.19% 15 and lifetimes of more than 1 720 000 h. 16 Despite the advantages of Zn 1−x Mg x O NPs as the ETL and the achieved efficiency of QLEDs equivalent to that of organic LEDs (OLEDs), 17−20 many challenges still remain in both scientific research and commercial applications. 21 One of the key issues is to control the reproducibility and size uniformity of In this work, we explored a new method to synthesize Zn 1−x Mg x O NPs using the Corning advanced-flow reactor (AFR). The AFR platform can potentially overcome the issues associated with the traditional one-pot colloidal synthesis method, such as the size nonuniformity, poor reproducibility, and short lifetime in storage.…”

“…Despite the advantages of Zn 1– x Mg x O NPs as the ETL and the achieved efficiency of QLEDs equivalent to that of organic LEDs (OLEDs), − many challenges still remain in both scientific research and commercial applications . One of the key issues is to control the reproducibility and size uniformity of Zn 1– x Mg x O NPs.…”

Patterning of quantum dot light‐emitting diodes based on IGZO films

“…13,14 There are a number of reports focusing on the stability of ETL as the ZnO-based NCs are chemically active and sensitive to the environment (temperature, oxygen, moisture, etc.). [15][16][17][18] On the other hand, there are obvious differences among the red, green, and blue quantum dots (QDs), especially the relatively higher conduction band maximum of blue QDs. [19][20][21][22][23][24] This may require different ETLs for different color QLEDs, i.e., the patterning of ETL (different ETL materials for different color pixels) is needed.…”

“…There are a number of reports focusing on the stability of ETL as the ZnO‐based NCs are chemically active and sensitive to the environment (temperature, oxygen, moisture, etc.) 15–18 . On the other hand, there are obvious differences among the red, green, and blue quantum dots (QDs), especially the relatively higher conduction band maximum of blue QDs 19–24 .…”

Inverted organic photovoltaics with a solution-processed Mg-doped ZnO electron transport layer annealed at 150 °C

“…For example, such a layer has been incorporated in quantum dot and perovskite light-emitting diodes, either on its own or in combination with another ZnO layer to inject electrons. [38][39][40][41][42][43][44][45][46] Such studies have demonstrated that doping ZnO with Mg can lead to a more balanced injection and therefore an increase in the maximum external quantum efficiency and current efficiency. The improvement has been attributed to a decreased conductivity and an upward shi of the conduction band of the Mg-doped ZnO ETL compared to the undoped ZnO ETL.…”