I have been researching OCSs and recently shifted focus to the PM6:Y6 active layer. For dissolving this active material, I use chloroform with a 0.5% vol/vol 1-chloronaphthalene solvent additive. The process involves stirring and heating (~50 ºC) inside a tightly closed vial overnight within in the glovebox for subsequent spin-coating. However, I've encountered an issue with the extreme volatility of chloroform, leading to changes in the solution's concentration and affecting device performance. Any recommendations, for example, a type of vial that can be tightly closed to decrease chloroform evaporation, would be highly appreciated.