Temperature- and field-dependent quantum efficiency in tris-(8-hydroxy) quinoline aluminum light-emitting diodes

Temperature- and field-dependent electroluminescence and quantum efficiency have been investigated in tris-(8-hydroxy) quinoline aluminum (Alq(3)) lig ht-emitting diodes over the temperature range from 10 to 300 K. At lower ap plied voltage, two peaks have been observed in the quantum efficiency with temperature. The two peaks are attributed to the deep trap levels (high-tem perature regime) and shallow trap levels (low-temperature regime) in Alq(3) . With increasing voltage, the high-temperature peak shifts toward lower te mperature but no significant shift of the low-temperature peak is observed. At voltage around 10 V, superposition of two peaks causes the apparent sat uration in the low-temperature regime of the quantum efficiency. (C) 2001 A merican Institute of Physics.