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

• Main Authors: Hyo-Min Kim, Wonkyeong Jeong, Joo Hyun Kim, Jin Jang
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Nanomaterials
• Subjects: alkali metal carbonate; metal oxide; Mg doped ZnO; operational lifetime; QLED
• Online Access: https://www.mdpi.com/2079-4991/10/12/2423

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.