NEUTRONOPV - New neutron techniques to probe bulk heterojunction solar cells with graded morphologies – understanding the link between processing, nanostructure and device performance
(FP7/H2020 – Grant agreement number: 658391)
Gabriel Bernardo, Andrew J. Parnell, David Lidzey, Stephen M. King, Richard A. L. Jones
This project’s primary aim was to contribute to a better understanding of the relationship between processing conditions, active layer morphology and device performance in polymer solar cells (PSC), providing the understanding needed to guide the search for practical processing routes. The secondary aim was to develop the potential of Small Angle Neutron Scattering (SANS) for studying the morphology of thin films as used in real bulk-heterojunction (BHJ) solar cells, as an exemplar of the emerging classes of functional organic and hybrid devices which are expected to have significant economic and societal impact in coming decades.

NANODISPERSE - Dispersion of Functionalized Fullerenes in Polymer Nanocomposites
Hugo Gaspar, Liliana Fernandes, Nadya Dencheva, Zlatan Denchev, Gabriel Bernardo
In this project, polymer-fullerene blend systems were studied to understand from a fundamental level their structure-property relationships, using a combination of detailed materials characterization such as Small Angle Neutron Scattering (SANS), Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The immediate motivation for working with fullerenes comes from the field of photovoltaics where fullerene-polymer mixtures play a critical role in the properties of the devices. However, the results of this work have far wider implications in both fundamental understanding of generic polymer-nanoparticle interactions as well as in other technological applications, such as water purification where the fullerene acts as a catalyst for oxygen excitation.

Pressure Induced Mixing and Crystallization Effects in Materials for Polymer Photovoltaic Cells
Paulo Pereira, Loic Hilliou, Júlio Viana, David G. Bucknall, Gabriel Bernardo
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.