Computational Insights Into All-Fused Ring Non-Fullerene Acceptors for Enhanced Stability and Performance.

The chemical stability and performance of non-fullerene acceptors (NFAs) are critical for achieving high power conversion efficiency (PCE) and device stability. This study presents a novel computational design strategy for addressing key stability challenges. The photochemical stability is improved by removing the vinylene bridge between the core and end groups, which often causes degradation and photoisomerization. All-fused non-fullerene acceptors (AFNFAs) are designed by directly fusing high-performance end groups with core units such as Y6 (FY6) and ITIC (FITIC). Density functional theory (DFT) and molecular dynamics simulations show that the new molecules exhibit superior optoelectronic properties and favorable bulk-phase morphologies. The results also show highly ordered packing of acceptor dimers and efficient charge transport. Additionally, the voltage losses associated with exciton diffusion, dissociation, and energetic disorder in electron affinities are minimal. Overall, the proposed AFNFAs with imide end groups emerge as promising candidates for stable high-performance acceptors in organic solar-cell applications.