Fluoroalcohol-Mediated Solvation for Self-Assembled Molecules Anchoring Optimization Toward High-Performance Organic...

The uniform chemisorption of phosphonic acid-based self-assembled molecules (SAMs) onto the indium tin oxide (ITO) substrate is fundamentally hindered by the thermodynamic limitations of interfacial heterocondensation reactions, limiting the photovoltaic performance and stability of organic solar cells (OSCs). Herein, we develop a facile solvation regulation strategy to address this issue by utilizing the solvation effect of 2,2,2-trifluoroethanol (TFE) solvent. It is found that TFE can form a robust intermolecular hydrogen bond (O─H···O═P) with the SAM 2PACz, thereby polarizing the phosphoryl moiety (P═O) bond, enhancing the electrophilicity of the phosphorus atom, and substantially elevating the thermodynamic driving force for the interfacial anchoring reaction. Consequently, the assistance of TFE for 2PACz leads to a more uniform and stronger anchoring 2PACz layer onto the ITO substrate, elevating the power conversion efficiency (PCE) of the D18:L8-BO-based device from 19.79% to 20.60%. Additionally, this solvation strategy effectively improves the scale-up processing capability of 2PACz, delivering a PCE of 15.89% in the flexible OSC module with an active area of 11.9 cm². Furthermore, the mechanism established in this work demonstrates broad universality across diverse active layer systems, SAM materials, and fluoroalcohol solvents.