Intrinsic Role of Volatile Solid Additive in High‐Efficiency PM6:Y6 Series Nonfullerene Solar Cells

Abstract

Organic nonfullerene solar cells (ONSCs) have made unprecedented progress; however, morphology optimization of ONSCs is proven to be particularly challenging relative to classical fullerene-based devices. Here, a novel volatile solid additive (VSA), 2-hydroxy-4-methoxybenzophenone (2-HM), is reported for achieving high-efficiency ONSCs. 2-HM functions as a universal morphology-directing agent for several well-known PM6:Y6 series nonfullerene blends, viz. PM6:Y6, PM6:BTP-eC9, PM6:L8-BO, leading to a best efficiency of 18.85% at the forefront of reported binary ONSCs. VSAs have recently emerged, while the intrinsic kinetics is still unclear. Herein, a set of in situ and ex situ characterizations is employed to first illustrate the molecule-aggregate-domain transition dynamic process assisted by the VSA. More specifically, the role of 2-HM in individual donor PM6 and acceptor Y6 systems is unlocked, and the function of 2-HM in altering the PM6:Y6 bulk heterojunction blends is further revealed for enhanced photovoltaic performance. It is believed that the achievement brings not only a deep insight into emerging volatile solid additive, but also a new hope to further improve the molecular ordering, film microstructure, and relevant performance of ONSCs.

Impact of Intermolecular Interactions between Halogenated Volatile Solid Additives and the Nonfullerene Acceptor in Organic Solar Cells

“…Processing solvent and volatile solid additives are proven to be practical approaches for optimizing the active layer morphologies in high-performing NFA OSCs. [19][20][21][22] Nevertheless, due to the high boiling point, e.g., 1-chloronaphthalene [23] and 1,8diiodooctane, [24,25] the solvent additive residue remains within the active layer, causing degradation of the devices. In contrast, volatile solid additives could be efficiently evaporated from the active layer upon thermal treatment.…”

Film-formation dynamics coordinated by intermediate state engineering enables efficient thickness-insensitive organic solar cells

“…29 Two-dimensional (2D) 1 H-1 H nuclear magnetic resonance (NMR) measurement was further employed to validate this molecular interaction between TBr and Y6, where Nuclear Overhauser Effect Spectroscopy (NOESY) spectra can provide satisfying information about protons in the range of less than 5 Å in space. 30 As highlighted in Fig. 1d, there are multiple crossover signals at the C 11 H 23 proton signal at the 7.59 ppm location in the Y6:TBr blend, whereas no signal appears at the same location in the neat Y6 case (Fig.…”

Additive-assisted strategy for high-efficiency organic solar cells

“…Other volatile solid additives with distinct chemical structures were also investigated. 121–123 Zhan et al applied ferrocene (Fc, Fig. 1d) in PM6:Y6 based OSCs.…”