Polymer solar cells offer a competitive alternative to existing conventional solar cells due to their light weight, semi-transparency, low cost, mechanical flexibility and ability to be printed with similar manufacturing techniques to newspapers and labels. While processing of polymer solar cell interfacial layers is from eco-friendly printing inks, the photoactive layer is still deposited from toxic chlorinated solvents. Three key avenues are being pursued by the polymer solar cell research community to move away from chlorinated solvent processing, (1) aqueous colloidal nanoparticle inks, (2) synthetic modification of the semiconducting polymers and fullerenes with polar functional groups, and (3) utilising available modelling packages to determine material Hansen solubility parameters (HSP) and trialling unconventional solvent systems. This talk will give an overview of the three strategies, followed by a detailed account of the researcher’s work in the space of aqueous colloidal nanoparticle ink technology. Nanoparticle photoactive layers have a dual advantage, the second advantage being they offer control of the semiconducting polymer and fullerene film morphology on the nanoscale, a factor critical to the optimisation of exciton dissociation efficiency and charge transport in these devices. The use of advanced synchrotron X-ray characterisation techniques have enabled the material-morphology-performance relationships to be unravelled in these devices, and thereby accelerated the development of nanoparticle polymer solar cells.
Dr Natalie Holmes was awarded her PhD in Chemistry from the University of Newcastle in 2015, as an Australian Renewable Energy Agency (ARENA) scholar, where she was involved in the development of aqueous nanoparticle inks for the fabrication of polymer solar cells. Her research investigated the structure-function relationships in these devices through the use of synchrotron-based X-ray microscopy, electron microscopy and spectroscopy, which led to the publication of several of the seminal articles in the emerging research field of nanoparticle polymer solar cells. Shortly after finishing her PhD, Natalie took up a Visiting Postdoctoral Research Associate position at Karlstad University, Sweden where she investigated other environmentally-friendly solvent options for coating semiconducting polymers and fullerenes for solar cell fabrication. Natalie now works as a Postdoctoral Research Associate at the Centre for Organic Electronics (COE), University of Newcastle in materials science, developing nano- and micro-structured functional polymeric materials for organic electronic sensor and solar cell applications.