Water-based solar cells over 10% efficiency: designing soft nanoparticles for improved processability

Organic semiconductors are typically dissolved in organic solvents that are harmful to human health and the environment. To overcome this issue, these materials can be dispersed in water as nanoparticles to provide aqueous inks for more environmentally friendly solar cell manufacturing. Herein, we report the design of “soft” PTQ10 :Y6 nanoparticles to decrease the annealing treatment (130 °C/5 minutes) needed for processing the active layer and increase the conversion efficiency above 10%. Taking advantage of the nanoprecipitation mechanism, nanoparticles with intermixed donor/acceptor domains and a low degree of crystallinity were synthesized. Solar cells made with these nanoparticles were more efficient and needed less energy to be processed than those made from miniemulsion inks, in which Y6 crystallinity was more important. They even reached more than 90% of the performances of devices made from organic solvents, closing the gap with the classical toxic process.