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To optimize the electron-hole balance by controlling the electron transport layer in (ETL) in quantum dots light emitting diodes (Q-LEDs), ZnO was modified by doping with Mg and Ga and applied to commercial Q-LEDs as ETLs. By doping ZnO nanoparticles with Ga, the electrons easily inject due to the increased Fermi level of the ZnO nanoparticles. By co-doping with Mg, the valence band maximum of the ZnO nanoparticles deepens and blocks the holes more efficiently. Also at the interface of the QD/ETL, Mg reduces non-radiative recombination by reducing oxygen vacancies on the surface of the ZnO nanoparticles. As a result the maximum luminance and the maximum luminance efficiency of the Q-LEDs increased to 43 440 cd m-2 and 15.4 cd A-1 respectively. These results increased by 34%, 10%, and 27% for the maximum luminance and 450%, 88%, and 208% for maximum luminance efficiency with undoped ZnO and Mg or Ga single doped ZnO ETL. The effect of Mg and Ga co-doping on the maximum luminance and maximum luminescence efficiency will be discussed. [ABSTRACT FROM AUTHOR]