Supriya Surana oral presentation (OB1-Thu1-1-3)
Matrix effects in doped Organic Light Emitting Diode (OLED) layers
1 imec, Kapeldreef, 3001 Heverlee, Belgium
2 Instituut voor Kern- en Stralingsfysica - KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium
3 Universite Catholique de Louvain, Place Louis Pasteur 1, 1348 Louvain-la-Neuve, Belgium
Electrically doped transport layers are an avenue to highly efficient organic electronic devices such as OLEDs or organic photovoltaic cells. However, in order to monitor dopant diffusion, composition depth profiling of these layers needs to be achieved . One factor that impedes compositional analysis of organic layers composed of binary blends is the matrix effect .
To study the matrix effect, we depth profile a dopant, F6-TCNNQ in matrices of three different hosts- α-NPD, TCTA and Spiro-TAD, finding that in each of these host matrices, the steady state intensity of the negative ion of the full F6-TCNNQ molecule first increases with increasing dopant content and then, beyond a certain F6-TCNNQ composition, starts to drop (Fig. 1). We quantify this matrix effect and demonstrate that it has a linear relationship with the concentration of nitrogen in the host.
At the interface of the layer with the substrate, we observe a huge enhancement of the full molecule from the host material in the positive polarity which features even in depth profiles of the pure host layers- indicating that diffusion of the dopant is not a likely cause of the enhancement. We explain the enhancement by an ionization effect due to a transfer of electrons from the host material to the substrate for energy level alignment .
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This project has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement No 646176 (EXTMOS).