Electrical Doping Stabilizes Organic Nanoparticle Dispersions for the Eco-Friendly Fabrication of Solar Cells

Nanoparticle dispersions allow the use of eco-friendly processing agents for the solution deposition of organic semiconductor thin-films for photovoltaic and other optoelectronic applications. Omitting surfactants, which are commonly used to stabilize dispersions, is essential to not jeopardize the solar cell performance. In this work, electrical doping is used to charge the organic nanoparticles. The resulting electrostatic repulsion between the nanoparticles stabilizes the dispersion. Different doping concepts are deployed, compared and their effect on the nanoparticle stabilization is explored. Preference is given to volatile dopants which evaporate from the nanoparticulate light-harvesting layer after thin-film deposition. Finally, using electrical doping and the corresponding electrostatic stabilization, novel surfactant-free nanoparticle dispersions from high-performance organic semiconductors are synthesized by nanoprecipitation, giving rise to record solar cell power conversion efficiencies beyond 10%.<br/>F. Manger et al., Adv. Funct. Mater. 2202566 (2022); F. Manger et al., Adv. Energy Mater. 2202820 (2023)