Regulating H-Aggregation via a Thiazole-Modified Acceptor-Based Packing Reshaper Toward Highly Efficient and Stable Organic Solar Cells.

Organic solar cells (OSCs) based on non-fullerene acceptors have achieved power conversion efficiencies (PCEs) exceeding 20%. However, their long-term stability remains limited by uncontrolled molecular aggregation and morphological degradation in bulk heterojunction (BHJ) films. Here, we report a thiazole-based acceptor (BDTTz) as a molecular packing reshaper that selectively regulates acceptor H-aggregation to enable efficient and stable OSCs. Theoretical calculations reveal stronger interactions between BDTTz and L8-BO than between BDTTz and PM6, enabling targeted reinforcement of acceptor packing without disrupting donor organization. Incorporating BDTTz into PM6:L8-BO blends extends the acceptor crystallization window from 32 to 48 ms, increases the coherence length from 50.21 to 57.17 Å, and raises the glass-transition temperature from 104°C to 142°C, thereby suppressing molecular diffusion and stabilizing the blend morphology. The optimized morphology facilitates charge transport, suppresses the nonradiative recombination, and mitigates the electron-phonon coupling, affording a champion PCE of 20.66% with an extended T80 lifetime of 1200 h under continuous illumination and heating conditions. Moreover, BDTTz incorporation into D18:L8-BO blends yields a champion PCE of 21.08%. This work establishes a molecular-level packing-reshaping strategy for developing high-efficiency and long-term-stable OSCs.