A quantum dot device includes an anode, a hole injection layer on the anode, a hole transport layer on the hole injection layer, a quantum dot layer on the hole transport layer, and a cathode on the quantum dot layer, wherein a highest occupied molecule orbital (HOMO) energy level of the quantum dot layer is greater than or equal to about 5.6 electronvolts (eV), a difference between a HOMO energy level of the hole transport layer and the highest occupied molecule orbital energy level of the quantum dot layer is less than about 0.5 eV, the hole injection layer has a first surface contacting the anode and a second surface contacting the hole transport layer, and a HOMO energy level of the first surface of the hole injection layer is different from a HOMO energy level of the second surface of the hole injection layer.