The effective recombination of electrons and holes affects the electroluminescence efficiency of organic light-emitting diodes. In this work, the photoelectric characteristics for the structure of ITO/TPD/Alq3/Mg:Ag with various thicknesses of hole blocking layer is investigated. The results show that the HBL of Alq3 do impede the movement of holes and increase the electron-hole recombination. In addition, a thickness of approximately 6 nm for the HBL is found to have good optical performance for the trade-off between cost and EL efficiency.
