Efficient Organic Light Emitting Diodes Using Solution-Processed Alkali Metal Carbonate Doped ZnO as Electron Injection Layer

Guo Chen; Feiyang Liu; Zhitian Ling; Pengpeng Zhang; Bin Wei; Wenqing Zhu

doi:10.3389/fchem.2019.00226

Efficient Organic Light Emitting Diodes Using Solution-Processed Alkali Metal Carbonate Doped ZnO as Electron Injection Layer

Front Chem. 2019 Apr 16:7:226. doi: 10.3389/fchem.2019.00226. eCollection 2019.

Authors

Guo Chen¹, Feiyang Liu¹, Zhitian Ling¹, Pengpeng Zhang¹, Bin Wei¹, Wenqing Zhu¹

Affiliation

¹ Key Laboratory of Advanced Display and System Applications, Shanghai University, Ministry of Education, Shanghai, China.

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.

Keywords: alkali metal carbonate; doped ZnO; electron injection layer; organic light emitting diodes (OLED); solution process.