Towards Highly Efficient Upscaled Organic Solar Cells: Solvents, Fabrication and The Role of Charge Carrier Dynamics

Organic solar cells (OSC) using non-fullerene acceptors in the Y6 family have now surpassed 19% efficiency. However, these lab-scale, state-of-the-art devices are usually processed using halogenated solvents, which are not suitable for up-scale. As the solvent used during deposition of the OSC’s active layer has a significant impact on its microstructure, and therefore the device performance, one of the first steps towards industrialization is to start with materials that are already soluble in greener alternatives.<br/><br/>Moreover, there is still a large performance gap between spin-coated, hero cells and large-scale modules. This is due, among other factors, to the difficulties in maintaining an optimal active layer morphology when switching to industrial fabrication techniques. To bridge this gap, it is paramount to study the photophysics of devices made with scalable techniques, such as blade coating and slot-die coating.<br/><br/>In this work, we demonstrate highly efficient organic solar cells fabricated with spin-coating, blade coating, and slot-die coating techniques, using PM6 and Y12 in o-xylene as electron donor and electron acceptor materials, respectively.<br/>We then investigate the differences and similarities between these techniques with a variety of optoelectronic techniques, including transient photovoltage, charge extraction, and GIWAXS, to determine charge carrier dynamics, morphology, photovoltaic performance, and stability.<br/><br/>Finally, this work demonstrates the application of green-solvent processed OSCs as semi-transparent devices with over 40% visible transmittance and a fully solution-processed stack.