The present invention relates to an organic light-emitting device comprising: a cathode; an anode; a light-emitting layer provided between the cathode and the anode; and a heterocyclic compound represented by chemical formula (1). The present invention comprises: a first electron transport layer provided between the cathode and the light-emitting layer; and a second electron transport layer provided between the cathode and the first electron transport layer, wherein the second electron transport layer comprises a host material, comprising one or more of the compounds represented by chemical formulas (3)-(5), and one or more n-type dopants selected from alkali metals and alkaline earth metals.