Controlling Morphology and Improving Stability with High-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.