Quantum-dot light-emitting diodes (QD-LEDs) having a sputtered transparent metal oxide (TMO) electron-transporting layer (ETL) are studied. SnO2 and ZnO were examined as a candidate of the ETL considering their electronic bands. A relation between the exponent value, m, of the power law shaped current density curves and the luminance performance is found. The larger m value caused the higher luminance performance, and the m value could be controlled by changing the ETL deposition and treatment conditions. The highest luminance performance in this work was obtained from the QD-LEDs with the ZnO ETLs sputtered with an Ar/O-2 mixed sputtering gas and treated with an O-2 plasma. We find a method to control the defect density in TMO ETLs by changing the ETL deposition and surface-treatment conditions, the relation between the current curve shape and the luminance performance, and, as a result, an way to improve the luminance performance of QD-LEDs having a sputtered TMO ETL.