Pressure Induced Mixing and Crystallization Effects in Materials for Polymer Photovoltaic Cells
(PTDC/CTM-POL/120843/2010)

There is currently great interest in organic electronics, largely due to the ease with which polymers can be manufactured at much lower costs compared to their inorganic counterparts. The most popular route to process polymers in organic electronic applications is currently through spin coating from dilute solutions. However, conjugated polymers require organic ligands to make them soluble in organic solvents and hence solution processable and these ligands usually have a detrimental effect in the electronic properties of the materials because they hinder a more efficient crystallization of the rigid conjugated backbones. By comparison, in the commodity plastics industry solid state processing is ubiquitous, for mixing and forming of polymers and blends. The approaches used in these cases have not to date been adopted for organic electronics, but offer unique opportunities for both mixing and forming organic materials which cannot be processed either by solution or vapour phase. In this project, the forming and crystallization behaviour of polymer semiconductor materials was explored when subjected to pressure and temperature with the aim of attaining a better understanding of the solid state processing-structure-property relationships in these systems.

Publications
1. Alexandre Rodrigues, Deb Nabankur, Loic Hilliou, Júlio Viana, David G. Bucknall, Gabriel Bernardo, "Low Temperature Solid State Processing of Pure P3HT Fibers", AIP Advances 3, 052116 (2013)
http://dx.doi.org/10.1063/1.4806764

2. Alexandre Rodrigues, M. Cidália R. Castro, Andreia S. F. Farinha, Manuel Oliveira, João P.C. Tomé, Ana V. Machado, M. Manuela M. Raposo, Loic Hilliou, Gabriel Bernardo, "Thermal stability of P3HT and P3HT:PCBM blends in the molten state", Polymer Testing 32 (2013) 1192-1201
http://dx.doi.org/10.1016/j.polymertesting.2013.07.008

3. Hugo Gaspar, Liliana Fernandes, Lúcia Brandão, Gabriel Bernardo, "Increase in thermo-oxidation stability of conjugated polymers at high temperatures", Polymer Testing 34 (2014) 183-191
http://dx.doi.org/10.1016/j.polymertesting.2014.01.013

4. Gabriel Bernardo, Deb Nabankur, Paulo Pereira, Lúcia Brandão, Júlio Viana, David G. Bucknall, "Solid State Low Temperature Extrusion of P3HT Ribbons", Applied Physics A 117 (2014) 2079-2086
http://dx.doi.org/10.1007/s00339-014-8622-x

5. Lúcia Brandão, Júlio Viana, David G. Bucknall, Gabriel Bernardo, "Solventless processing of conjugated polymers A review", Synthetic Metals 197 (2014) 2333
http://dx.doi.org/10.1016/j.synthmet.2014.08.003


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