Electron injection via pentacene thin films for efficient inverted organic light-emitting diodes

Abstract

We report on the fabrication of efficient inverted organic light-emitting diodes (IOLEDs) using pentacene films as an electron injection/transport layer between Al and Alq(3) layers. These IOLED devices turn on at 4.7 V and exhibit a luminous efficiency of 9.5 cd/A without any dopants or reactive metals. Analysis using space-charge-limited characteristics of electron-only devices and ultraviolet photoelectron spectroscopy measurement of metal/organic interfaces indicates that the efficient IOLED characteristics can be attributed partly to the electron mobility of pentacene that is 10(2)-10(4) times larger than that of Alq(3) and to the effective reduction in injection barrier at contacts.