Controlling Morphologyand Improving Stability withHigh-Boiling-Point Additive for Efficient Organic Solar Cells

The rapid advancement of solar photovoltaic technology underscores the growing significance of organic solar cells (OSCs) in renewable energy solutions. A critical challenge in optimizing OSC performance lies in achieving precise control over active layer nanomorphology. In this study, we innovatively introduce a high-boiling-point liquid additive, 1,2,4-trichlorobenzene (1,2,4-TCB), as a superior alternative to the conventional additive 1,8-diiodooctane (DIO). Compared to DIO, 1,2,4-TCB significantly enhances the molecular ordering of acceptors and improves the miscibility between the donor (D18) and acceptor (Y6) materials, leading to a notable increase in power conversion efficiency (PCE) from 17.56% to 18.80%. It has been revealed that 1,2,4-TCB promotes superior molecular packing, particularly for acceptor molecules from the grazing incidence wide-angle X-ray scattering. The contact angle measurements further demonstrate improved donor–acceptor miscibility, resulting in an optimized bicontinuous interpenetrating network morphology. This morphology effectively enhances exciton separation, facilitates charge transport, and minimizes recombination losses. In addition to performance improvements, 1,2,4-TCB-based devices exhibit exceptional photostability (<i>T</i>₈₀ = 981 h) and storage stability (<i>T</i>₈₀ = 2708 h), significantly outperforming their DIO-based counterparts. These findings not only establish the potential of high-boiling-point additives like 1,2,4-TCB in boosting OSC efficiency and stability but also provide a promising strategy to advance the commercial viability of this technology.