Showing papers by "Torsten Fritz published in 1999"

Controlled doping of molecular organic layers: Physics and device prospects

Abstract: We show that organic dye layers of various matrix materials can be efficiently p- and n-doped in a controlled way by cosublimation. As an example for p-doping, we discuss cosublimation with the strong organic acceptor F 4-TCNQ, a fluorinated form of tetracyanoquinodimethane (TCNQ). The semiconductor properties of such doped layers are studied by combined Seebeck and conductivity measurements for zinc phthalocyanine as a model matrix with molar concentrations of F 4-TCNQ between 0.2% and 1%. With increasing doping, we observe a smooth shift of the Fermi level towards the valence state of the matrix and a drastic and superlinear increase of the conductivity, reaching 10−2S/cm for the highest dopant concentrations. The Seebeck data indicate that doped ZnPc behaves similarly to crystalline semiconductors with a temperature independent hole density for all doping ratios. To demonstrate the use of these doping concepts, we present first promising application examples of doped phthalocyanine layers: Mip-type diodes with high rectification ratio and low series resistance and organic two layer light emitting diodes with low onset voltage.