Implementing Inkjet Printed Transparent Conductive Electrodes in Solution Processed Organic Electronics

Through the use of solution-based materials, the field of printed organic electronics has not only made new devices accessible, but also allows the process of manufacture to move toward a high throughput industrial scale. However, while solution-based active layer materials in these systems have been studied quite intensely, the printed electrodes and specifically the transparent conductive anode have only relatively recently been investigated. In this progress report, the use of metal nanoparticles within printed organic electronic devices is highlighted, specifically their use as replacement of the commonly used indium tin oxide transparent conductive electrode within organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). A cross fertilization between the applications is expected since an OPV device is essentially an inversely operated OLED. This report aims to highlight the use of inkjet-printed nanoparticles as cost-effective electrodes for printed optoelectronic applications and discusses methods to improve the conductive and interfacial properties. Finally, in an outlook, the use of these types of metal nanoparticle inks to manipulate light management properties, such as outcoupling, in the device is investigated

Up scalable ITO free organic light emitting diodes based on embedded inkjet printed copper grids

We report on ITO-free OLEDS with a transparent hybrid Cu nanoparticle grid/PEDOT:PSS electrode processed in ambient conditions. An experimentally based methodology was implemented, where studies on alternative PEDOT:PSS derivatives and Cu grid design were performed, to gradually increase the efficiency of lab scale ITO-free OLEDs. To further increase electrode performance, inkjet-printed (IJP) Cu-grids are embedded to flatten the electrode, reduce leakage current and enhance homogeneity and efficiency. Finally, embedded Cu based ITO-free OLEDs showed current and power efficiencies comparable to reference ITO-based OLEDs. Methods to manufacture large area flat embedded IJP Cu-electrodes on glass and flexible substrates are presented and upscaling prospects of the proposed ITO-free electrode are discussed

Development and in vitro evaluation of nitrendipine transdermal formulations using experimental design techniques

In the present study nitrendipine was incorporated into gels and its efficacy to permeate human epidermis was examined in vitro. A preliminary study was carried out in order to estimate the effect of the type of enhancer, the concentration of enhancer and the concentration of gelling agent on the flux of nitrendipine, using a 23 factorial design. The type of enhancer and the concentration of enhancer were further evaluated as they were found to be important for nitrendipine flux, while the concentration of the gelling agent was kept at its optimum level in all experiments. In order to increase further the flux of nitrendipine, the combination of two enhancers, glycerol monooleate (GMO) and N-methyl-2-pyrrolidone (NMP), which act via different mechanisms, at three concentration levels was examined, using the response surface method. The results indicate that higher flux values were obtained when NMP was greater than 4.5% w/w and GMO between 5.0 and 9.5% w/w, in the vehicle. © 1995

Development and in vitro evaluation of nimodipine transdermal formulations using factorial design

The in vitro permeation of nimodipine through human cadaver skin, as a preliminary step toward the development of a transdermal therapeutic system, was investigated. In vitro release studies were carried out using modified Franz diffusion cells and human epidermal membrane, taken from full-thickness cadaver skin by heat separation technique. To estimate the effect of the type of enhancer, the concentration of enhancer and the concentration of the gelling agent on the permeation of nimodipine, a 23 factorial design was involved. The type of enhancer was further evaluated, because it was found to be important for the permeation of nimodipine; the concentration of enhancer and the concentration of the gelling agent were kept at their optimum levels in all experiments. Six groups of enhancers (alkanols, alkanoic acids, alkanoic acids ethyl esters, caprylic acid alkyl esters, essential oils and some other enhancers) were examined for their ability to increase the permeation of nimodipine. It was found that myristyl alcohol, caprylic acid, L-menthol, and oleic acid gave better permeation rates at 24 hr, with oleic acid being the better enhancer, and higher permeation rates at 48 and 72 hr were achieved only when cineol was used

Worldwide outdoor round robin study of organic photovoltaic devices and modules

Accurate characterization and reporting of organic photovoltaic (OPV) device performance remains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using "suitcase sample" approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where the samples and the testing equipment were integrated in a compact suitcase that served both as a sample transportation tool and as a holder and test equipment during testing. In addition, an internet based coordination was used via plasticphotovoltaics.org that allowed fast and efficient communication among participants and provided a controlled reporting format for the results that eased the analysis of the data. The reported deviations among the laboratories were limited to 5% when compared to the Si reference device integrated in the suitcase and were up to 8% when calculated using the local irradiance data. Therefore, this method offers a fast, cheap and efficient tool for sample sharing and testing that allows conducting outdoor measurements of OPV devices in a reproducible manner