In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells. Issue 9 (9th August 2020) - Yang, Dan
Abstract: The development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1, 8‐diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing‐incidence small/wide‐angle X‐ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole‐based polymer (PPDT2FBT) and [6, 6]‐phenyl‐C71‐butyric acid methyl ester (PC71 BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid–liquid phase, while phase separation mainly occurs in the liquid–solid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large‐scale fabrication of organic photovoltaics. Abstract : A detailed investigation of the polymer morphology and crystallinity development during the film formation process in the printed bulk heterojunction films shows differences in the kinetics depending on the used solvent additive. The choice of solvent additive is essential for the print process.