1 December 1997 Does tris-(8-hydroxyquinolinato) aluminum transport holes?
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Abstract
Hole transporting properties of tris-(8-hydroxyquinolinato) aluminum (Alq) were investigated using time-of-flight (TOF) photocurrent transients and photoinduced discharge techniques. A thin layer of Alq was inserted between two hole transporting layers. Within the time domain of the photocurrent transients,the fraction of holes escaping from one side of the Alq layer to the other side is strongly field, temperature, and Alq thickness dependent. The results of photoinduced discharge experiments indicate that eventually the holes escaped the trilayer samples. The injection barrier is estimated to be approximately 0.12 eV. The hole penetration range is estimated to be 10-30 angstrom in the range of field strengths studied, therefore suggesting the recombination zone of electrons and holes in Alq-containing electroluminescent (EL) devices is confined close to the interface of Alq and the hole transporting layer. The results demonstrate the importance of the hole injection barriers and hole trapping to the performance of organic EL devices using Alq as the electron transporting and emissive layer.
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Liang-Bih Lin, Ralph H. Young, David S. Weiss, Samson A. Jenekhe, Paul M. Borsenberger, "Does tris-(8-hydroxyquinolinato) aluminum transport holes?", Proc. SPIE 3148, Organic Light-Emitting Materials and Devices, (1 December 1997); doi: 10.1117/12.284176; https://doi.org/10.1117/12.284176
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