An ultra-thin hole-injection buffer layer using Ta2O5 by RF magnetron sputtering in organic light-emitting diodes has been fabricated. With the property of high dielectric constant, Ta2O5 can be expected to be a good buffer layer material and thus enhance the emission performance of the OLED. The Ta2O5 film blocks part of the injected holes from the ITO anode to the organic layer (TPD) and improves the balance of hole and electron injections. The power efficiency of the device with the Ta2O5 film can be increased by approximately 20%. (C) 2003 Elsevier Science Ltd. All rights reserved.