Closing the Lab-to-Fab Gap with Inkjet-Printed Organic Photovoltaics

Abstract

Inkjet printing promises to be an invaluable technique for processing organic solar cells with key advantages such as low material consumption, freedom of design and compatibility with different types of flexible substrates making it suitable for large-area production. However, one concern about inkjet printed organic solar cells is the common use of chlorinated solvents during the ink formulation process. While chlorinated solvents suit the inkjet printing process due to their high boiling points, suitable viscosity, and excellent solubility of organic donor and acceptor compounds, they still pose some risks for both human health and the environment, excluding them from being the ultimate choice for large-area production.

As a step towards commercialization of OPV, we demonstrated the possibility to close the laboratory to fabrication gap, through the engineering of environmentally friendly inks, using a blend of non-halogenated benzene derivatives solvents optimized to meet the viscosity and surface tension requirements for the inkjet printing process.

Starting from using the non-fullerene acceptor O-IDTBR combined with the commercially available donor polymer P3HT we obtained solar cell device with efficiency up to 4.73% - the best efficiency achieved by the P3HT:O-IDTBR system processed with all non-halogenated solvents via inkjet printing. We also delivered highly transparent active layer with device power conversion efficiency of up to 10% with a highly efficient blend of polymer donor PTB7-Th in combination with the ultranarrow band gap NFA IEICO-4F, using hydrocarbons solvent. Lastly, we demonstrated both high efficiency, transparency, and stability by presenting a novel approach based on NFAs consisting of lowering the donor:acceptor ratio in the photoactive layer ink formulations, resulting in more stable devices with comparable power conversion efficiencies to those achieved by lab methods.

This breakthrough in ink engineering paves the way in closing the lab-to-fab gap in organic photovoltaic using the low-cost, high throughput inkjet printing technology while considering both environmental and health-conscious mass production and device stability of organic photovoltaics.