The carrier-trapping effect of dye doped in Alq

Abstract

The electroluminescence (EL) of an organic light-emitting diode specially fabricated with a pure thin dye layer 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) of 1-nm thickness inserted at the interface between N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine and tris(8-quinolinolato) aluminum has been investigated. The EL behavior of this device changed dramatically at a driving voltage of about 12.25V, which has been ascribed to the breakage of the thin DCJTB layer. It is suggested that not only such thin layer of DCJTB can transport electrons and holes, but also trap them. A comparison of the EL performance with four other devices confirms this mechanism. Therefore, the high efficiency and long life of the dye doped Alq devices are attributed to the hole and electron trapping effect and the high photoluminescence efficiency of the dye.