Investigation of internal processes in organic light-emitting devices using thin sensing layers

Systematic studies are a prerequisite for a detailed understanding of the internal processes in organic semiconductors and devices, which is of great importance for optimizing organic light-emitting diode performance. Devices based on small molecules are especially well-suited for introducing thin layers (< 10 nm), which in turn can be used as analysis and sensing tools. We use combinatorial methods to fabricate matrices of 10 x 10 individual devices on single substrate in order to ensure reliable and reproducible datasets. We present selected examples to illustrate the strength of this method. These experiments include layer thickness variations in a multilayer system to optimize device performance. A thin metallic and dye-doped sensing layer is inserted into the device to derive the distribution of the electrical field and exciton density, respectively. By means of thickness-dependent photoluminescent measurements we gain insight into luminescence quenching near interfaces. (C) 2003 Elsevier Science B.V. All rights reserved.