ZnMgO:ZnO composite films for fast electron transport and high charge balance in quantum dot light emitting diodes

Abstract

Electron transport and electron-hole balance are the essential processes that determine the efficiency and luminance of quantum dot light emitting diodes (QLEDs). Those structures with a good capability of fast electron transport and charge balance are needed. We developed a novel composite electron transport layer (ETL) consisting of zinc oxide (ZnO) and zinc magnesium oxide (ZnMgO) nanoparticles for the QLED devices, which can enhance EQE to 13.5%. It is 1.29 times and 1.33 times compared with that of pure ZnO and ZnMgO nanoparticles, respectively. The luminance intensity was increased up to 22100 cd/m2 at a voltage of 8.8 V. The current-voltage of electron-only devices measurement results indicate that the composite ETL generates higher current than the nano-particulate ZnMgO layer. Meanwhile, the QLEDs with ZnMgO:ZnO ETLs exhibit lower leakage current densities at the turn on voltage than that with pure ZnO ETL. Transient measurement results indicate that the composite ETL can keep a charge balance more effectively than a conventional ZnO nano-particulate layer.