The transient photovoltage of ITO/CuPc/Al is studied. The transient photovoltage under the Al side illumination is much greater than that under ITO side illumination. It is not negligible while light is almost completely absorbed by the Al layer. It seems that the light absorption of the Al layer could enhance the generation of the photoinduced carriers in the organic layer, which is further shown by the transient photovoltage study of ITO/Al/NPB/Au. A possible mechanism proposed is that the holes generated in the Al are because of light absorption that is injected from the Al to organic materials. This results in further charge separation by the internal built-in electric field.
Quantum decoherence in organic charge transport is a complicated but crucial topic. In this paper, several theoretical approaches corresponding to it, from incoherent to coherent, are comprehensively reviewed. We mainly focus on the physical insight provided by each theory and extent of its validity. The aim of this review is to clarify some contentious issues and elaborate on the promising perspectives provided by different approaches. The device model approaches based on both continuous and discretized treatments of the transporting layer will be first discussed. The prominent focus of this review will be devoted to the dynamic disorder model and its variants considering that it is the most promising approach to tackle charge transport problems in organic materials. We will also address other theories such as the variational method.
Non-monotonic, asymmetrical electric field dependence of photoluminescence(PL) intensity is observed in a monolayer sample of tris-(8-hydroxyquinoline) aluminum(AlQ) doped N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine(TPD). A possible model is proposed: the charge separation from the dissociated photoexcited excitons causes energy band bending in the organic films and improves the hole injection from the electrode, which brings about the extra fluorescence.This mechanism is further verified by a series of experiments using a series of samples, variously featuring symmetrical electrodes, block layers, and hosts with lower hole mobilities.
