Morphology effects on charge generation and recombination dynamics at ZnPc:C60 bulk hetero-junctions using time-resolved terahertz spectroscopy

The influence of growth temperature induced phase segregation and crystallinity in ZnPc:C-60 blend films on the charge generation and recombination dynamics is investigated with optical-pump terahertz-probe spectroscopy. While an ultrafast photo-induced charge generation process is observed for all morphologies, a subsequent sub-nanosecond photoconductivity rise depends on crystallinity and phase segregation. For higher intensities, the signal is dominated by a morphology-dependent bimolecular recombination process. High local mobilities of minimal mu similar to 0.3 cm(2)/Vs are found. The increase of photoconductivity with film growth temperature correlates with formerly observed device photocurrent improvements, (C) 2011 American Institute of Physics [doi:10.1063/1.3644129]