We demonstrate the possibility of controlling organic light-emitting diodes (OLEDs) efficiency with an optimized hole-delay layer (HDL) in order to achieve very high contrast ratio needed for active matrix display applications. No triplet exciton confinement structure and a molybdenum trioxide (MoO3) HDL at ITO/hole transport layer interface were used for a careful placing and adjusting of the exciton recombination zone. An optimized thickness of 50 nm thick MoO3 allows to cut off the efficiency at the black level of active matrix driving mode while it gets greater at higher luminance at high current density region over 20 mA/cm(2) compared to conventional device. Our suggested efficiency control way is believed to be very useful to future active matrix OLED displays. (C) 2014 Elsevier B.V. All rights reserved.