Gernot Mauthner

Inkjet printed polymer light-emitting devices fabricated by thermal embedding of semiconducting polymer nanospheres in an inert matrix

An aqueous dispersion of semiconducting polymer nanospheres was used to fabricate polymer light-emitting devices by inkjet printing in an easy-to-apply process with a minimum feature size of 20μm. To form the devices, the electroluminescent material was printed on a nonemitting polystyrene matrix layer and embedded by thermal annealing. The process allows the printing of light-emitting thin-film devices without extensive optimization of film homogeneity and thickness of the active layer. Optical micrographs of printed device arrays, electroluminescence emission spectra, and I∕V characteristics of printed ITO/PEDOT:PSS/PS/SPN/Al devices are presented.

Solution Processed Conjugated Polymer Multilayer Structures for Light Emitting Devices

We study the feasibility of semiconducting polymer nanospheres deposited from miniemulsions as an approach to form organic multilayer structures and devices from an all solution based process. A detailed study of the wetting and film forming properties of the dispersed semiconducting polymer nanospheres on different polar and non-polar organic surfaces is given. The transmission and fluorescence properties of the polymer multilayer structures are studied. Organic light emitting devices based on such multilayer structures are presented and their properties are discussed.

Cryptand based solid-state electrolytes in polymer light-emitting devices

In order to gain improved insight into the fundamental mode of operation of light-emitting electrochemical cells (LECs), LECs were prepared from a solid-state electrolyte, consisting of the cryptand (Kryptofix® 222, [2.2.2] cryptand) and lithium triflate, and a blue emitting low-Stokes-shift poly(para-phenylene). The devices reveal LEC-like characteristics, however, their evolution appear on a longer time scale, which is a consequence of reduced cation conductivity of the [2.2.2] cryptands compared to commonly used ion conductors and decelerated electrochemical n doping near the cathode. It is possible to study the location and direction of the emission zone shift during device operation.

Interface and ion-induced optoelectronic effects in thin films of poly(p-phenylene)s functionalised with ion-transporting side chains

Abstract We report on investigations of thin films of homopolymers and copolymers consisting of a conjugated poly(p-phenylene) (PPP) backbone and oligo(ethylene oxide) (OEO) side chains of varying chain length in order to supply a conjugated backbone with an ion-transporting functionality. The optical properties of these polymeric mixed ionic–electronic conductors (PMIECs) reveal a response upon complexation of the OEO side chains with an alkali metal salt (lithium triflate). In addition, the rather polar nature of the OEO side chains and the non-polar nature of the PPP backbone can be applied to control the polymer/substrate interfacial properties. These topics were investigated by means of UV/VIS/NIR absorption measurements, along with photoinduced absorption spectroscopy. Infrared and Raman spectroscopy complemented this work to determine the amount of ion dissociation.

Tracking ion mediated changes in the optical properties of a polymeric mixed ionic–electronic conductor: an application for a chemical sensor system

Abstract In this study, we use photoinduced absorption (PIA) spectroscopy to show that the triplet exciton properties of an oligo(ethylene oxide) (OEO) grafted conjugated polymer (PPP-R10) are very sensitive to the presence of ionic species. Investigations were performed on thin spin-cast films of this polymeric mixed ionic–electronic conductor. Since the ion-coordinating side-chains are directly attached to the conjugated backbone, an ion induced order–disorder transition affects the characteristics of the conjugated polymer, which is observable as a blue shift in the π–π * absorption, the triplet exciton absorption spectra, and also manifests in other triplet exciton properties, like their lifetimes and the bimolecular annihilation parameter. Based on the sensitivity of the triplet exciton properties such polymers can be envisioned in the application in chemical sensor systems.

Photophysics and optoelectronic properties of a poly(p-phenylene)-type polymer in different kinds of light-emitting devices

We report on the photophysics of the pristine oligo(ethylene oxide) side-chain grafted polymer PPP-OR11 and the polymer blended with the lithium salt lithiumtriflate. The side-chains render the polymer soluble in common organic solvents and in addition provide ionic conductivity, which is important for the application of the polymer as mixed ionic-electronic conductor for instance in light-emitting electrochemical cells (LECs). The optoelectronic properties of the polymer were studied for two types of light-emitting devices, first in light emitting diodes and secondly in LECs. From these investigations it is evident that in polymer light-emitting diodes (PLEDs) several degradation processes caused by defects on the PPP backbone deteriorate the color stability. These defects are induced either by the oxidation of the polymer or the aluminum deposition process upon device fabrication. Contrarily, LECs fabricated from the same polymer provide color stable blue emission. The color stability of the LEC can be explained by the fact that the recombination zone is shifted from the cathode/polymer interface in PLEDs to the non-doped intrinsic zone between the p- and n-type regions of the LEC, avoiding emission from aluminum evaporation induced defects.