Active layer and coating issues

To characterize the coating performances of the various solutions, we developed roll-to-roll and roll-to-plate coating systems. The solution can be extruded via a slit nozzle added to the roll-to-roll system which functions similarly to the nozzle in the slot-die system. The film thickness can be controlled by the coating speed and slit gap. PEDOT PSS, P3HT PCBM, PBDTTTrPCBM, ZnO nanoparticle and interface dipole solutions have been tested by using this coating system. 

Because the flow issues during drying directly affect the coating quality and uniformity, basic coating tests are required using various solvents for the functional materials in OPVs. 

Basically, the film thickness can be determined by the viscosity of the solution, among other factors. Given that the viscosity of the solution is proportional to the concentration, when we change the solution concentration to control the thickness, the film thickness can be roughly estimated by the following relations  

In practical experiments, however, it is hard to control the viscosity precisely because the viscosity is not always linearly proportional to the solution concentration. However, we can also control the thickness by adjusting the coating speed. This is similar to spincoating, where adjustment of the coating speed is the easiest way to control thickness. 

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Layered and spinel materials have been used successfully as intercalation-type cathode active materials in commercial Li-ion batteries. The physical and chemical properties, electrochemical reactions, structure evolution mechanisms, stability and safety issues have been widely investigated. Based on comprehensive fundamental researches, since 1980s, their electrochemical performances are improved continuous after various modifications, such as doping, surface coating, forming solid solution and composite, controlling morphology, size and crystallinity. Here, basic features of layered and spinel materials are summarized. 

A second option is to apply the membrane on the particle level (millimeter scale) by coating catalyst particles with a selective layer. As a third option, application at the microlevel (submicrometer scale) is distinguished. This option encompasses, for example, zeolite-coated crystals or active clusters (e.g., metal nanoparticles). Advantages of the latter two ways of application are that there are no sealing issues, it is easy to scale-up, the membrane area is large per unit volume, and, if there is a defect in the membrane, this will have a very limited effect on the overall reactor performance. Because of these advantages, it is believed that using a zeolite... 

An alternative to grafted PNIPAAm surfaces, which requires previous activation of the supporting substrate, is offered by multilayer polymer assemblies, such as chitosan-grafted-PNIPAAm and alginate multilayered films (Martins et a/., 2011). The layer-by-layer approach allows mild conditions for fabrication and precise control over the thickness of the coatings, which is a relevant issue for modulating cellular adhesiveness. 

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