Electrolyte; Organic photovoltaics; Morphology control; Bulk heterojunction; Cyanine dye; Counterion
Gesevičius Donatas, Neels Antonia, Duchêne Léo, Hack Erwin, Heier Jakob, Nüesch Frank (2019), Physical vapour deposition of cyanine salts and their first application in organic electronic devices, in Journal of Materials Chemistry C
, 7(2), 414-423.
Gesevičius Donatas, Neels Antonia, Yakunin Sergii, Hack Erwin, Kovalenko Maksym V., Nüesch Frank, Heier Jakob (2018), Superweak Coordinating Anion as Superstrong Enhancer of Cyanine Organic Semiconductor Properties, in ChemPhysChem
, 19(24), 3356-3363.
Gesevičius Donatas, Neels Antonia, Jenatsch Sandra, Hack Erwin, Viani Lucas, Athanasopoulos Stavros, Nüesch Frank, Heier Jakob (2017), Increasing Photovoltaic Performance of an Organic Cationic Chromophore by Anion Exchange, in Advanced Science
One research domain in organic photovoltaics is devoted to the questions on how to improve the nanomorphology of so called bulk heterojunction solar cells, and more fundamentally, what is the optimal morphology after all. Bulk heterojunction morphologies in thin films evolve during solvent evaporation by a quench of the solution into the unstable region of the solution phase diagram (via spinodal decomposition). We propose to investigate bulk heterojunction morphologies of small molecule absorber dyes with PCBM. Cyanine dyes are a class of ionic compounds, and control of the morphology can be achieved via the dissociation behavior of the counterion associated with the dye. A dissociated counterion is capable to strongly influence the miscibility of a ternary fluid and can also tune the morphology of a phase separating system. The effect on morphology usually leads to smaller features and is related to the emergence of electrostatic interactions associated with charge separation between the domains thus preventing further coarsening. Typically such mechanisms were investigated for aqueous polyelectrolyte / nonionic polymer systems. For small molecules in organic solvents, these processes are only rarely studied. This novel aspect will be the main focus of the proposed research. In particular we seek to exploit this effect in the development in solar cells which has not been done yet. We will systematically investigate the relation “dissociation - ternary solution phase diagram - thin film morphology - solar cell performance”. The challenge is to find meaningful correlations between phase diagram and film morphology. Phase diagrams represent equilibrium situations, however, during the fast solvent evaporation the system may not be able to adapt to equilibrium and a non-equilibrium morphology is frozen in. Goal of the project is to understand the morphology evolution in thin films and to optimize the device performance by morphology control.