Hydrogen-Bond-Mediated Solid Additives Enabling Enhanced Bi-Continuous Interpenetrating Network for 20.29% Efficiency Layer-by-Layer Organic Solar Cells.

Layer-by-layer (LbL) processing technology offers precise control over vertical phase separation in organic solar cells (OSCs), yet optimizing the underlying donor morphology to facilitate acceptor infiltration remains a critical challenge. Herein, we report two novel solid additives of BQ and BBQ, which feature a D-A-D type 2,5-di(thiophen-2-yl)pyrazine conjugated skeleton, to regulate the D18 donor layer in D18/L8-BO devices. The BQ molecule contains carbamate side chains that form robust intramolecular hydrogen bonds with the pyrazine core, locking the backbone into a planar and pseudo-pentacyclic structure. This structural feature enhances the crystallinity and face-on orientation of D18 film, fostering an optimized fibrillar network. This network acts as an ideal scaffold for subsequent deposition of L8-BO, thus resulting in a pseudo-bulk heterojunction with expanded interfacial area for exciton dissociation and continuous channels for charge transport. Consequently, the BQ-processed LbL-OSCs achieve an impressive efficiency of 20.29%. In contrast, the brominated analogue BBQ exhibited relatively excessive phase separation, which disrupted the active layer homogeneity and hindered optimal molecular packing. This work highlights the efficacy of hydrogen-bond-mediated solid additives in fine-tuning the morphology of the donor layer for high-performance LbL-OSCs.