Transient photovoltage study on the dynamics of excitons and carriers in tris-(8-hydroxyquinolinato)aluminum

摘要

Transient photovoltage (TPV) was performed on the ITO/tris-(8-hydroxyquinolinato)aluminum (AlQ)/silver device to study the dynamics of carriers. It has been previously reported that typical TPV results in organic semiconductors show no more than one turning point of voltage polarity, where interfacial exciton dissociation and carrier drift are responsible as suggested by the conventional model. By contrast, two polarity turning points were observed in our TPV studies, for which the conventional model fails to explain and thus a more detailed model is proposed to add the diffusion of carriers. The new model is further supported by the TPV evolution study where the effect induced by insertion of a thin LiF layer between AlQ and silver was examined. Our new findings may give a better understanding of optoelectronic dynamics in organic semiconductors.