Abstract
In this study, we demonstrate highly efficient, inverted organic light-emitting diodes (IOLEDs) using solution-processed alkali metal carbonate doped ZnO as an electron injection layer (EIL) and tris-(8-hydroxyquinoline) aluminum (Alq3) as an emitter layer. In order to enhance the electron injection efficiency of the IOLEDs, the ZnO EIL layers were modified by doping various alkali metal carbonate materials, including Li2CO3, Na2CO3, K2CO3, and Cs2CO3, using the low-temperature wet-chemical method. Compared to the control neat ZnO EIL-based IOLEDs, the alkali metal carbonate doped ZnO EIL-based IOLEDs possess obviously improved device performance. An optimal current efficiency of 6.04 cd A−1 were realized from the K2CO3 doped ZnO EIL based IOLED, which is 54% improved compared to that of the neat ZnO EIL based device. The enhancement is ascribed to the increased electron mobility and reduced barrier height for more efficient electron injection. Our results indicate that alkali metal carbonate doped ZnO has promising potential for application in highly efficient solution-processed OLEDs.
Highlights
Organic light-emitting diodes (OLEDs) have been extensively investigated as a promising technology for energy-saving lighting and large-area flexible displays (Kido et al, 1995; Forrest, 2004; Sasabe and Kido, 2010; Higuchi et al, 2015; Li et al, 2016)
To systemically investigate the effect of group I elements doping on properties of the ZnO films and the doped ZnO film based inverted OLEDs (IOLEDs), we introduced various alkali metal carbonates (M2CO3, M = Li, Na, K, and Cs) with various doping ratios into ZnO film using the low-temperature wet-chemical doping method
Based IOLEDs and the corresponding energy-level diagram. In this IOLED device, the Alq3 film acts as an emitter layer, the NPB
Summary
Organic light-emitting diodes (OLEDs) have been extensively investigated as a promising technology for energy-saving lighting and large-area flexible displays (Kido et al, 1995; Forrest, 2004; Sasabe and Kido, 2010; Higuchi et al, 2015; Li et al, 2016). The device performance of doped ZnO based IOLEDs. The ZnO:M2CO3 EILs in this study were fabricated by a simple wet-chemical doping method using the blend aqueous solution of M2CO3 and Zn-ammine complex as the precursor.
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