The electrical and optical properties of organic light-emitting devices (OLEDs) with three periods of 4,7-diphenyl-1,10-phenanthroline (BPhen)/aluminum tris(8-hydroxyquinolate) (Alq(3)) multiple heterostructures acting as an electron transport layer (ETL) were investigated. While the leakage current of OLEDs with multiple heterostructures was smaller than that of OLEDs without multiple heterostructures, the luminance efficiency was larger than that of OLEDs without multiple heterostructures. The BPhen layers in the multiple heterostructures blocked holes from the emitting layer (EML) to the ETL, and they enhanced the electron injection from the cathode to the EML, resulting in an increase in the luminance efficiency.