I have to deposit Active layer of PV in this configuration P3HT/P3HT:ICBA/ICBA. There are different solvents for P3HT and ICBA. Anyone have idea how to deposit by using spin coating technique. Thank you
Dear Muhammad,
as long as you deposit same materials on top of each other, you will always get some parts of the deposited bottom layer dissolved (as there is a certain solubility in the used solvent). This we could show for small molecules in "Formation of blade and slot die coated small molecule multilayers for OLED applications studied theoretically and by XPS depth profiling". So your final stack will have a change in film thicknesses or composition over film height respectively compared with trials when you just deposite the single layers independently. Question is the degree of intermixing. So far it is hard to calculate that. For high molecular weight polymers we were able to show first experimental results in calculations (see publications "Interdiffusion in Polymeric Multilayer Systems Studied by Inverse Micro-Raman Spectroscopy" and " Modeling of interdiffusion in poly (vinyl acetate)–poly (methyl methacrylate)–toluene multicomponent systems").
For this complex system, I recommend to adopt the process parameters for the single layers first and than apply it to the complete stack. If you aim at very low degrees of intermixing, the solvent should be removed very quickly. So low solvent contents and higher temperatures are recommended. Finally one has to be aware, that mechanical forces could rub off the underlying layer.
Hope this helps you!
Kind regards,
Sebastian
I have tried toluene with 1,2 dichlorobenzene (DCB) in fabrication of this multi layer structure, but i think its not chemically compatible with toluene. Is there any other solvent which can be used to make bi-layer organic solar cell. I want to use two different solvents which must be compatible and should dissolve with each other. I want to mix other solvent with chloroform, or chlorobenze or 1,2 dichlorobenzene. Thank you
Dear Muhammad,
I recommend to perform calculations with the modified UNIFAC approach for the Liquid-Liquid-Equilibria (LLE) if you don't want to run experiments. Several parameters are available in publications - others may be bought via the Dortmund Data Bank (www.ddbst.com). In my experiments I was mainly checking for systems which separate - so I cannot recommend you any compositions of solvents. A problem could be water. If water is absorbed by one of the solvents during your experiments it will not mix with toluene.
Br,
Sebastian
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