In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells

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 (PC71BM). 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.

Revealing Donor–Acceptor Interaction on the Printed Active Layer Morphology and the Formation Kinetics for Nonfullerene Organic Solar Cells at Ambient Conditions

“…In Figure 5a, the intense and broad ring located around 1.3 Å −1 originates mainly from the scattering of the CB solvent, which is in agreement with earlier studies. [ 47 ] As the solvent evaporates, the scattering contribution of CB is reduced, whereas the (010) Bragg peak of the crystallites in the blend located at ≈1.6–1.8 Å −1 becomes more and more distinct. As seen in Figure 5d, the (010) Bragg peak becomes more pronounced with increased intensity and a slight shift from its initial position.…”

“…In stage IV, for CB the intensity of the Bragg peak of the donor decreases while crystallite size and stacking distance slightly increase, suggesting the stabilization of the crystallites. [ 47 ] For the acceptor, the intensity increases slightly, crystallite size decreases, and the stacking distance remains unchanged. In contrast, in case of CF the intensity, crystallite size, and stacking distance of the donor all slightly decrease, whereas for the acceptor, the intensity increases but size and distance decrease.…”

High‐Efficiency (16.93%) Pseudo‐Planar Heterojunction Organic Solar Cells Enabled by Binary Additives Strategy

“…At present, the introduction of additives is a good way to induce crystallization of polymer donors and small acceptors, which have been widely used to optimize the morphology of BHJ OSCs. [ 32–34 ]…”

Understanding the Microstructure Formation of Polymer Films by Spontaneous Solution Spreading Coating with a High‐Throughput Engineering Platform

“…Hence, we can conclude that the influence of BP on the amount of amorphous phase is general. [ 45 , 46 ] This notion, obtained from a selection of 4 samples, does however not preclude that other factors such as the aromaticity of the additive, may also play a role; these relationships will be studied by GPR in the following section.…”