Optical and Electrical Properties of Plasmonic Electrodes for Inverted Fabrication of Organic Semiconductor Devices

Metal electrodes are playing an increasingly important role in controlling photon absorption and in promoting optimal light management in thin film semiconductor devices. In organic optoelectronics, the conventional fabrication approach is to build the device on top of a transparent electrode, with metal electrode deposition as the last step. This makes it challenging to control the surface of the metal electrode to promote good light management properties. An inverted fabrication approach that builds the device on top of a metal electrode, makes it possible to control the morphology of the metal surface to achieve a variety of photonic and plasmonic behavior in optoelectronic devices. Silver (Ag) is the most suitable metal for fabrication of nanostructured electrodes with plasmonic behavior (i.e. plasmonic electrodes) because of its low parasitic absorption loss and high reflectivity. In this project, we describe the facile fabrication of silver nanoparticle (AgNP) plasmonic electrodes and study their physical and optical characteristics. Then, we investigate the photonic and electrical behavior of the plasmonic electrodes when interfaced with poly(9,9-dioctylfluorene- alt-benzothiadiazole) (F8BT) organic semiconducting polymer thin films. According to the current-voltage characteristics of hole-only devices with and without plasmonic electrodes, we conclude that AgNP plasmonic electrodes have comparable electrical behavior to planar metal electrodes while having superior light management capability.