Two types of blue organic light emitting diodes with different structure have been fabricated. The maximum brightness and luminous efficiency for two devices are 3700 cd/m 2, 6123 cd/m 2 and 0 78 lm/W, 0.83 m/W respectively. It is demonstrated that a blocking layer can effectively ragulate the recombination area and obtain the desired light emission. However, the lifetime of the two devices are quite different. Luminance and durability characteristics of those devices are well explained and compared based on energy levels diagrams.