 In this study, researchers investigated the effects of additive 1-chloroenethylene, CN, on the formation of Y6, PM6 films during spin coating. They found that CN leads to incomplete film formation due to its slow evaporation rate compared to the solvent, which requires additional time for complete film formation. Additionally, CN must be removed before the film can reach a smooth surface. To do so, the researchers added a second layer of DIN from methanol, which acts as an anti-solvent for CN, allowing it to quickly evaporate and leave behind a smooth surface. With this method, solar cells featuring a high CN concentration of 5% were able to achieve comparable performance to those with lower concentrations between 0.5% and 1%. This article was authored by Timo Robb, Tobias Seewald, Stefan Kraner, and others.