Layer-by-layer blade-coated organic solar cells with non-halogenated solvents and non-halogenated additive via adjusting morphology and crystallization

Abstract

Developing high-efficiency organic solar cells (OSCs) by layer-by-layer (LBL) blade-coating using non-halogenated solvents is eco-friendly and scalable for industrial production of OSCs. Therefore, searching for non-halogenated solvent additives and gaining insights into the morphological tuning mechanism are urgent for advancing the OSCs prepared by LBL blade-coating. We have investigated the effect of non-halogenated solvent additive 1,2-dimethylnaphthalene (DMN) in the upper o-Xylene (o-XY) solution of Y6 on the film formation kinetics of the LBL blade-coated PM6/Y6 active layer by in situ absorption spectroscopy. It is found that DMN induces nucleation and crystal growth of Y6 molecules twice during the LBL blade-coating process, promoting the formation of a nano-fiber phase separated and excellent crystalline morphology in the LBL PM6/Y6(o-XY + DMN) active layer and improving the exciton dissociation and charge extraction. Finally, a high power conversion efficiency (PCE) of 16.15% is achieved for the OSCs prepared using all non-halogenated solvents and LBL blade-coating. Furthermore, a large-area and high geometric fill factor OSC module with a PCE of 12.64% is fabricated based on the LBL PM6/Y6(o-XY + DMN) active layer, demonstrating the potential of a non-halogenated solvent additive for the eco-friendly large-scale fabrication of OSCs.