A hole-blocking layer, 4,7-diphenyl-1,10-phenanthroline (Bphen), was introduced between the emission layer (EML) and the electron-transporting layer (ETL) for a europium complex based organic red light-emitting device. Such a structure helps to reduce hole leakage from the EML into the ETL, resulting in improved purity of emissive light. Optimum Bphen thickness of around 10 nm was observed to produce a current efficiency of 3.1 cd/A and brightness of 465.2 cd/m(2) at 14 V. With 10 nm Bphen layer, the red emission spectrum shows excellent color saturation with Commission Internationale De L'Eclairage coordinates of (0.64, 0.33) at 7 V (C) 2009 Elsevier Ltd. All rights reserved.